Vykon Hvac

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PARTNER INFORMATION

TRIDIUM

Vykon HVAC release 3.4.46_HVAC.2.2

DOCUMENT RELEASE DOC REFERENCE: teu-jb-101_16.doc DATE 18th

Mar 1016 PAGE 1 of 284

Release_3.4.46_HVAC.2.2

Vykon HVAC

Application guide

Copyright TRIDIUM. INC.

TRIDIUM EUROPE LTD


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PARTNER INFORMATION

TRIDIUM




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Contents

PARTNER INFORMATIONTRIDIUM




Contents:

Contents: ................................................................................................................... 3Introduction ............................................................................................................... 7Scope.......................................................................................................................... 7Acknowledgements and references........................................................................ 7The applications library............................................................................................ 9

Vykon HVAC applications ........................................................................... 11General applications (hvacAppsGeneral) ................................................... 11Heating plant applications (hvacAppsHeatingPlant) ................................... 12Heat delivery applications (hvacAppsHeatDelivery) ................................... 12Cooling plant applications (hvacAppsCoolingPlant).................................... 13Cooling delivery applications (hvacAppsCoolingDelivery) .......................... 13Air handling applications (hvacAppsAirHandling)........................................ 14Standard-applications and Mini-applications (hvacAppsGeneral)............... 15

Common functions ................................................................................................... 17Hysteresis.................................................................................................... 18Heat curve ................................................................................................... 20Adaptive optimum start optimiser ................................................................23Non adaptive optimum start optimiser......................................................... 26Setpoint change delay................................................................................. 28Application Status........................................................................................30

General functions and applications ........................................................................ 31The pump exercise application.................................................................... 32Alarms ......................................................................................................... 36Alarm indicator strategy...............................................................................38The holiday schedule application ................................................................40The time schedule application..................................................................... 43The outside temperature application ...........................................................49The average outside temperature application............................................. 53


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The night purge application ......................................................................... 57The fire override application ........................................................................ 62The trace heating application ......................................................................65

The Max 10 boilers application................................................................................ 67Overview ..................................................................................................... 67Boiler heat generation plant.........................................................................69System enablers, interlocks and alarms......................................................70Desired supply temperature and heat demand control strategy ................. 73Delta T, boiler staging and sequence control strategy ................................ 76Transport system and pump sequence strategy......................................... 79

The radiator group application ................................................................................ 81Overview ..................................................................................................... 81Common strategies ..................................................................................... 84Control on supply temperature.................................................................... 88Control on space temperature..................................................................... 93

The radiant panels application ................................................................................ 99Overview ..................................................................................................... 99Common strategies ..................................................................................... 102Control on supply temperature.................................................................... 106Control on space temperature..................................................................... 111

The heating delivery system application ................................................................117Overview ..................................................................................................... 117Control strategy ........................................................................................... 121

The heating non controlled group application....................................................... 129Overview ..................................................................................................... 129Control strategy ........................................................................................... 131

The domestic hot water (DHW) application............................................................ 135Overview ..................................................................................................... 135Control strategy ........................................................................................... 137

The Max 4 chillers application ................................................................................. 145Overview ..................................................................................................... 145Cooling plant................................................................................................ 146


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System enablers, interlocks and alarms ..................................................... 147Chiller staging and sequence control on direct strategy ............................. 152Chiller staging and sequence control on supply temperature strategy ....... 156Chiller staging and sequence control on load power strategy..................... 158Chiller staging and sequence control staged externally strategy ................ 161Transport system and pump sequence strategy ......................................... 163

Cooling delivery - The delivery system application............................................... 165Overview ..................................................................................................... 165Control strategy ........................................................................................... 169

Cooling delivery - The pre-controlled group application...................................... 175Overview ..................................................................................................... 175Common strategies ..................................................................................... 178Control on supply temperature .................................................................... 185Control on space temperature.....................................................................187

The Air Handling Unit application ........................................................................... 189Overview ..................................................................................................... 189Application selection.................................................................................... 190System enablers, interlocks and alarms ..................................................... 191Control strategy overview............................................................................ 192Delayed start-up method strategy ...............................................................194Heating and cooling staging strategy ..........................................................202Low / High fan speed control strategy.........................................................208Fan modulating control strategy ..................................................................210Filters strategy............................................................................................. 212Supply fan control strategy..........................................................................213Extract fan control strategy .........................................................................215Heater control strategy ................................................................................ 217Chilled water cooler control strategy ...........................................................224DX chiller control strategy ........................................................................... 227Humidifier control strategy........................................................................... 231Heat recovery run around coil strategy .......................................................234Heat recovery wheel control strategy..........................................................237Heat recovery plate heat exchanger (modulating bypass) strategy............ 239Heat recovery plate heat exchanger (open / close bypass) strategy .......... 243Heat recovery mixing dampers strategy......................................................245


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The extract fan application.......................................................................................251Overview ..................................................................................................... 251System enablers, interlocks and alarms......................................................252Extract fan control strategy overview ..........................................................252Fan On / Off control strategy....................................................................... 253Fan Low / High control strategy................................................................... 255

The heat recovery unit (HRU) application...............................................................257Overview ..................................................................................................... 257System enablers, interlocks and alarms......................................................258Control strategy overview............................................................................ 258Combined supply fan and extract fan control strategy................................ 259Separate supply fan and extract fan on / off control strategy...................... 262Separate supply fan and extract fan modulating control strategy ...............265Bypass air damper open / close control strategy ........................................ 270Bypass air damper modulating control strategy .......................................... 271

Default alarms............................................................................................................ 277Logging ...................................................................................................................... 281

Overview ..................................................................................................... 281Logging frequency and capacity..................................................................281Default logging............................................................................................. 281

Related documents ................................................................................................... 284Document Control ..................................................................................................... 284

This is a 284 page document at A4


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Introduction





Introduction

Vykon HVAC provides a new approach to creating heating, ventilating and air-conditioning controlapplications within a standard Tridium JACE controller. Powered by the industry-leading NiagaraAXFramework, it dramatically speeds up control system engineering whilst ensuring consistency andaccuracy of set-up.

For the installer, to the engineer and end-user, Vykon HVAC has been designed to provide productivity,reliability and efficiency from a simple to use, intuitive software based solution. With a web browserinterface for remote maintenance and a future-proof ability to adapt along with a buildings lifespan thebenefits of Vykon HVAC set the benchmark for HVAC applications.

The use of standardised applications provides the framework to control any location. Although each VykonHVAC installation will be different in option choices and settings, as each is derived from a standardapplication source, it offers instant familiarity and versatility for the engineer.

Thanks to the power of the NiagaraAX framework you wont get bogged down with detailed programming.Configuring of Vykon HVAC is a truly automated experience. Applications come with default settings toensure your system works first time, every time and modifications can be made instantly offering totalflexibility and future-proof expansion.

As a solution which is delivered in a standard JACE controller, Vykon HVAC seamlessly connects to thecontrols automation network and operates alongside other application solutions. It is a scalableimplementation which supports standard NiagaraAX connectability to enterprise applications.

Scope

This document contains a detailed description of all the applications available in the Vykon HVAC release.

Summary of the applications library Mini applications General applications Super applications Standard applications

Acknowledgements and references

Most of the Vykon HVAC application control strategies are based upon industry standard principles andtechniques. The description of their operation in this guide contains content which has been collected from

several sources. Grateful acknowledgement is therefore made to the following:

Title Author Organisation

Application Guide AG 7/98 Library of systemcontrol strategies

AJ MartinCP Banyard

The Building Services Researchand Information Association (BSRIA)

Design Guide 2000 SeaChange SeaChange

Building Control Systems CIBSE Guide H CIBSE The Chartered Institution of Building ServicesEngineers (CIBSE)

Terminology and graphical symbols (VDI code ofpractice) DIN 1946 Part 1)

DIN Deutsches Institut fur Normung.e.V Berlin.(DIN)


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Introduction







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The applications library






Here is an overview of HVAC applications and strategies that comprise the Vykon HVAC applicationslibrary

Heating Systems

Heat generation Constant or modulating boilers Boiler status and system monitoring Individual boiler pumps and cut-off valves Single or twin primary pumps and cut off valves Shunt pump Delta T temperature and sequence control

Heat distribution (secondary circuits) Constant volume / variable temperature Constant temperature / variable volume Single or twin secondary pumps and cut off valves Radiators or radiant panels Indirect or direct domestic hot water system (DHWS)

Cooling Systems

Water chillers Packaged air cooled water chillers Chiller status and system monitoring Individual chiller pumps and cut-off valves Single or twin primary pumps and cut off valves Staged sequence control

Chilled water distribution (secondary circuits) Constant volume and variable volume Single or twin secondary pumps and cut off valves Pressure or temperature controlled Dew point control


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Air Handling Systems

Damper control Full outside air damper system

Filtration Air filter with pressure monitoring

Heat recovery Thermal wheel (constant speed or modulating) Mixing dampers Run around coil Fixed plate heat exchanger (constant or

modulating bypass)

Cooling coil

Chilled water (CHW) cooling coil Direct expansion (up to 4 stages of DX) cooling

coil

Heating coil Low temperature hot water (LTHW) heating coil

Humidification Steam humidifier (constant or modulating)

Supply fan Constant volume supply fan Two speed supply fan VAV main duct static pressure system -

supply fan speed control

Extract fan Constant volume extract fan Two speed extract fan Variable volume extract fan

Fire / smoke control

Fire / smoke control, plant shutdown Fire / smoke control, damper position

Control strategies for air handling systems Constant air volume system Variable air volume system

General control strategies

Time control Low temperature plant protection Summer condition Adaptive and non adaptive optimum start Night purge

Trace heating

Fire system interlock Fan overrun Pump prerun and overrun

Compensated control PID control Sequence control Delta T control Pump auto changeover

Pump exercise

Thermal flow Geo-thermal wells


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Vykon HVAC applications

Within the Vykon HVAC library, applications are categorised as either super-applications, general-applications, standard-applications or mini-applications and their definition determines the scope and type

of HVAC application.

Super-applications and general-applications form the core of the automated Vykon HVAC applicationlibrary because these applications provide complete controls flexibility and can all be set up and configuredwithout any recourse to programming with the Niagara

AXworkbench tool. The heating plant application is

an example of a super-application. General-applications are common applications which all HVAC controlsystems need and these are always loaded by default into every station. A time schedule or holidayschedule are examples of general-applications.

The Vykon HVAC New HVAC station wizard provides an easy to use intuitive method of selecting one ormore super-applications from the Vykon HVAC library for inclusion in a station. The super-applications,or general-applications can then be completely configured via the browser because they contain all the I/Oconfiguration, settings parameters, alarming, histories, graphics visualisation and other functionality in

common with any fully completed HVAC application. It is by using these applications that the Vykon HVACapplications engineering user can gain the maximum productivity in engineering time and reliability.

Mini-applications and standard-applications are the building-blocks of the super-applications becausethey contain fundamental hvac components and control strategies and also include appropriate graphics.These building blocks are made available in Vykon HVAC to the applications engineer so that, if required,they can be manually selected and configured to easily add new or extra controls functionality to anapplication whilst still maintaining the same overall look-and-feel of the super-applications. Roomsensor and PID Loop are examples of mini-applications, and Air heater, Thermal wheel and Heatpump are examples of standard-applications.

General applications (hvacAppsGeneral)

All the applications which make up the general applications can be inspected and used by the applicationsengineer by accessing them via the hvacAppsGeneral module in the palette. General applications(GeneralApp) is a super-application but breaks the rule of being available for selection in the New HVACstation wizard. This is because it is always automatically selected and available in every station because itis part of the default station which is used whenever the wizard creates a station. General applicationsconsist of some general station application configuration and some general-applications

General station application configuration

Station time and date display Generation of I/O module wiring schedules Reset push button configuration Alarm indication and control behaviour

General-applications

Pump exercise Holiday schedule application Time schedule application Outside temperature application Average outside air temperature applicatin Night purge application Fire override application Trace heating application


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Heating plant applications (hvacAppsHeatingPlant)

The applications which make up the heating plant applications can be inspected and used by theapplications engineer by accessing them via the hvacAppsHeatingPlant module in the palette. There is one

super-application in the heating plant module which is available for selection in the New HVAC stationwizard

Super-applications

Max 10 boilers: The Max 10 boilers application comprises monitoring and control facilities for aboiler system comprising up to 10 packaged boiler units. The application contains options fortemperature and sequence control as well as mechanical options such as on/off or modulatingboilers, individual boiler pumps with or without cut off valves and a range of shunt pumparrangements. Applications which are utilising a combined boiler-calorifier packaged unit are alsoaccommodated in the Max 10 boilers application.

Heat delivery applications (hvacAppsHeatDelivery)

The applications which make up the heat delivery applications can be inspected and used by theapplications engineer by accessing them via the hvacAppsHeatDelivery module in the palette. There arefive super-applications in the heat delivery module and they are all available for selection in the NewHVAC station wizard

Super-applications

Radiator group: The radiator group application provides a heating delivery secondary circuitcomprising pump, control valve, monitoring devices and control strategies to maintain theenvironmental temperature of a space which is heated with water filled radiators. The radiatorgroup application offers valve arrangement options for constant volume, variable temperature andconstant temperature, variable volume circuits as well as control using supply or space temperature

Radiant panels: The radiant panels application provides a heating delivery secondary circuitcomprising pump, control valve, monitoring devices and control strategies to maintain theenvironmental temperature of a space which is heated with water filled radiant panels. The radiantpanels application offers valve arrangement options for constant volume, variable temperature andconstant temperature, variable volume circuits as well as control using supply or spacetemperature.

Delivery system: The delivery system application provides a general purpose secondary circuit forthe delivery of heated water. It comprises maintained or modulating, single or twin pumparrangements, restricting or diverting control valve, monitoring devices and control strategies tomaintain the supply temperature and pressure of any connected secondary circuits. The deliverysystem is responsive to the demand of any secondary circuits that are connected to it as well asbeing able to communicate with the heat generating system for boiler demand temperature andboiler demand limiting

Non-controlled group: The non controlled group application provides a simple secondary circuitfor the delivery of heated water to heating devices. It contains no pumps nor controlled valve. Its

primary use is an un-controlled delivery system which can communicate with the heat generatingsystem for boiler demand temperature.

Domestic hot water (DHW): - The domestic hot water (DHW) application provides for acomprehensive range of mechanical equipment, control and protection strategies for thedistribution of tap water. Heat supply for the final DHW circuit may be supplied by electricity, gas orindirectly from a boiler system with or without a heat exchanger. Temperature protection strategiesare available for both the calorifier and DHW circuit as well as a high heat strategy specificallydesigned for Legionella prevention. The DHW application is able to communicate with the heatgenerating system for boiler demand temperature and boiler demand limiting. In addition the DHWapplication can also communicate with other heat distribution circuits to request DHW preferencepriority for heat supply.


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Cooling plant applications (hvacAppsCoolingPlant)

The applications which make up the cooling plant applications can be inspected and used by theapplications engineer by accessing them via the hvacAppsCoolingPlant module in the palette. There is just

one super-application in the cooling plant module and it is available for selection in the New HVAC stationwizard

Super-applications

Max 4 chillers: The Max 4 chillers application comprises monitoring and control facilities for achiller system comprising up to 4 packaged chiller units. The application contains options fortemperature and sequence control as well as mechanical options such as on/off chillers, single ortwin primary pumps and individual chiller pumps with or without cut off valves.

Cooling delivery applications (hvacAppsCoolingDelivery)

The applications which make up the cooling delivery applications can be inspected and used by theapplications engineer by accessing them via the hvacAppsCoolingDelivery module in the palette. There aretwo super-applications in the cooling delivery module and they are both available for selection in the NewHVAC station wizard

Super-applications

Delivery system: The delivery system application provides a general purpose secondary circuit forthe delivery of chilled water. It comprises maintained or modulating, single or twin pumparrangements, restricting or diverting control valve, monitoring devices and control strategies tomaintain the supply temperature and pressure of any connected secondary circuits. The deliverysystem is responsive to the demand of any secondary circuits that are connected to it as well asbeing able to communicate with the chiller system for chilled water demand temperature.

Pre-controlled group: The cooling delivery pre-controlled group application provides a chilledwater delivery secondary circuit comprising pump, control valve, monitoring devices and controlstrategies to maintain the chilled water (CHW) demand of a zone of mechanical equipment such asfan coil units (FCU) or chilled ceilings. The pre-controlled group application offers valvearrangement options for constant volume, variable temperature and constant temperature, variablevolume circuits as well as control using supply or space temperature.


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Air handling applications (hvacAppsAirHandling)

All the applications which make up the air handling applications can be inspected and used by theapplications engineer by accessing them via the hvacAppsAirHandling module in the palette. There are

three super-applications in the air handling applications module and they are all available for selection inthe New HVAC station wizard

Super-applications

Air handling unit: Air handling unit: An extensive air handling unit application comprisingmechanical systems for ventilation, heat recovery, humidification and methods for heating andcooling the supply air

Extract fan: The extract fan application comprises an extract fan which can either be an on/off ortwo speed Hi/Lo device.

Heat recovery unit (HRU): The heat recovery unit (HRU) application comprises a supply andextract fan in a unit which is also equipped with an air heat exchanger. The HRU is a simple way ofventilating a space when there is no direct need for any additional heating or cooling.


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Standard-applications and Mini-applications (hvacAppsGeneral)

These applications are made available for use by the applications engineer to create custom applicationsand add functionality to the super-applications. They can all be inspected and used by accessing them via

the hvacAppsGeneral module in the palette.

Standard-applications

Air heater Air cooler Air DX cooler Modulating humidifier On-off humidifier Thermal wheel Run-around coil Plate heat exchanger Dampers

AHU start functions Heat and demand control Heat-pump Cooling tower Weather station Thermal flow Geo-thermal wells

Mini-applications

Dampers (Air valves) (Register valve, Register valve 0-10v, Register valve Tri-state, Valve FDS)

ColdGeneration (Chiller) Fans (Fan, Fan 0-10v, Fan HiLo, Fan HiLo with IO) Functions (Adaptive OSC, Heating curve, Hysteresis Rel, Hsteresis Abs, Non-adaptive OSC, PID

loop) HeatGeneration (Boiler, Boiler 0-10v, Boiler HiLo, Boiler HiLo with IO, Boiler on-off 0-10v, Boiler on-

off tri-state) Pumps (Pump, Pump 0-10v) Sensors (Duct sensor, Outside sensor, Room sensor) Valves (Changeover valve 3-way, Valve 0-10v, Valve 2-way, Valve 3-way, Valve tri-state)


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Common functions




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Common functions

In this section are a number of functions which are common and used in more than one place in the super-applications and to avoid repetition, they are described here. Some all also available as mini-applicationsand can be found in various folders of the general applications module (hvacAppsGeneral) and.Functionsmodule (hvacFunctions)

Common functions

Hysteresis absolute (abs) [hvacAppsGeneral Functions] Hysteresis relative (rel) [hvacAppsGeneral Functions] Heat curve [hvacAppsGeneral Functions] Adaptive optimum start optimiser [hvacAppsGeneral Functions]

Non adaptive optimum start optimiser [hvacAppsGeneral Functions] Set point change delay (decrease value) [hvacFunctions Functions] Application Status


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Hysteresis

Overview

Hysteresis is used to filter signals so that the output reacts slowly by taking recent history into account. Inan HVAC application for example, a thermostat controlling a heater will turn the heater on when thetemperature drops below 5C, but will not turn it off until the temperature rises above 7C. Thus the on/offoutput of the thermostat to the heater when the temperature is between 5C and 7C depends on thehistory of the temperature. This prevents rapid switching on and off as the temperature drifts around theset point.

The hysteresis function that is used in Vykon HVAC has the additional functionality of time which furtherenhances the filtering of on/off control. There are also two variants of the hysteresis function, absolutehysteresis and relative hysteresis, which are used extensively in the Vykon HVAC applications.

Operation

Operation of both the absolute hysteresis (hysteresis abs) and relative hysteresis (hysteresis rel) isdescribed in Figure 1 and Figure 2 respectively below. Both versions offer two preset operational modes,heating and cooling and the output is an on or off value. The behaviour of the output of each of thesemodes is similar except that one is the inversion of the other. Note how the adjustable time delay offersanother level of filtering to the change of value. The hysteresis (rel) calculates the difference that themeasured input is away from a relative setpoint value input in order to determine the switching points.

C

Outside

airtemp.

Figure 1: Hysteresis (abs) operation

5

7

HeatOn

Off

Cool On

Off

00:10 00:20


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C

Outside

airtemp.

Figure 2: Hysteresis (rel) operation

9

12

HeatOn

Off

Cool On

Off

00:10 00:20

10

Setpoint

10


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Heat curve

Overview

The heat curve function is a method of adjusting a value, usually one which is used as a control loopsetpoint in accordance with some other temperature value. A typical example is for compensated watertemperature control where the flow water temperature setpoint is varied as a function of the measuredoutside air temperature. This is sometimes called weather compensation or compensated setpoint.

The heat curve function that is used in Vykon HVAC is designed to be a universal control device that can beused for any type of application which requires that an output value is set by the value of an input to aconfigured ratio. The heat curve has optional slope correction functionality which provides compensationfor those applications using non-linear control devices such as most varieties of valve.

OperationThe output value (Y) of the heat curve function is calculated using the input value (X) and a slope which isdefined by two co-ordinates X1/Y1 and X2/Y2. This fundamental relationship is simply described in Figure 1.

When the heat curve is used in its usual and default application mode, the input values of X1 and X2 are twovalues of an outside air temperature which would typically set the setpoint value of a loop controlling the

internal water flow temperature between values defined by Y1 and Y2. Operation is simple such that if theoutside air temperature was -10C or lower then the water flow temperature would control to 90C and asthe outside air temperature rose to 20C and above, control of the flow temperature would decrease in alinear manner to 20C. Figure 2 shows this relationship but please note that for this application the outputvalues of Y1 and Y2 are positioned on the Y axis in a reversed order of magnitude. To overcome thisapparent graphical discrepancy the heat curve has a standard configuration setting which allows the heatcurve to be displayed in a more usual fashion. This is also shown in Figure 2.

Figure 1: Fundamental heat curve operation

X

1X

2

Y1

Y2

Input

Output


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Notice that the heat curve display indicates what the value of the current measured input is (in this exampleOutside air temperature) and the value of the calculated output (in this example Flow temperature). Thevalues of X1/Y1 and X2/Y2 are user adjustable settings and the heat curve function also provides for both

maximum and minimum limits to be set on the output which will override any conflicting output from thecurve. These two values can optionally be set either by an external value from other control strategy logicor internal by a user setting. Figure 2 shows the heat curve with internal (user) settings.

In order to accommodate use of the heat curve in applications where the transfer ratio action is notreversed, it has an optional proportional configuration setting and an example of this is shown in Figure 3.Notice that Figure 3 also shows the heat curve with external maximum and minimum output value limitsettings.

Figure 2: Typical heat curve operation

-10 20

90

20

Outside air temperature

Flowtemperature

C

C

Figure 3: Proportional heat curve operation

20 50

30

40

Input temperature

Outputtemperature

C

C


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Slope factorThe slope factor is a means of altering the transfer ratio of the heat curve from being a simple straightlinear relationship to a more complex one. The slope factor is an adjustment which is applied at a point

which equal to 2/3 between the X1/X2 values. An example can be seen in the Figure 4. With a slope factorof 1.0 an output of 43.3C corresponds to an input of 10C. However with a slope factor of 1.5 the output islifted to 64.9 at the same input value. The linear slope effectively tilts at the 2/3 point on the x axes but theX1/Y1 and X2/Y2 values remain constant.

Figure 5 shows examples from the heat curve function

Figure 5: Slope factor in operation

Figure 4: Slope factor operation

-10

90

Input temperature

20

200 10

43.3

64.9

Slope factor = 1.5

Slope factor = 1

Slope factor = 1.5

Slope factor = 1

C

C

Outputtempe

rature


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Adaptive optimum start optimiser

Overview

Optimum start is used for the optimisation of start time for heating systems in intermittently occupiedbuildings with regular occupation profiles. Adaptive optimum start operation utilises an adaptive self-learning algorithm to achieve the defined comfort conditions at the start of the occupied period in theshortest possible time, thus minimising fuel consumption and thereby maximising energy efficiency.Optimum start control systems are now required by many statutory building regulatory bodies. Forexample, in the UK, optimum start is required for heating systems of over 100kW capacity and generallyrecommended for heating systems of over 30kW capacity.

In a heating application the optimum start strategy will switch on some time before the time that peoplearrive in the building, in order to heat the building up to its normal occupied temperature. This is known asthe preheat period. How long the preheat period needs to be depends on the outside temperature, thethermal response time of the building structure and of the heating plant, and the difference between thecurrent space temperature and desired space temperature at occupancy time. An optimum start strategy

monitors the outside temperature, and ensures that the preheat period is the correct length of time for thebuilding to reach occupancy temperature neither before nor after people arrive. This minimises energywastage by 'optimising' the preheat time.

An adaptive optimum start strategy will modify its preheat time algorithm after each plant operating periodusing knowledge of the time at which the space temperature setpoint was achieved or of the actual spacetemperature when normal plant operation at occupancy began. The algorithm is continually modified andthis iterative process modifies and adapts the algorithm to the particular building and installation and soimprove its performance. The optimum start operation terminates either when the space temperaturereaches its setpoint value or when occupancy time arrives and normal plant operation begins.

The optimum start function that is used in Vykon HVAC two variants, adaptive and non-adaptive and bothare used extensively in the Vykon HVAC applications. Three boolean signals are provided by the optimiser

for use by other HVAC applications. These are; Preheat, Occupancy and Combined. Figure 1 shows asummary of the Vykon HVAC adaptive optimum start optimiser.

Figure 1: Adaptive optimum start optimiser

Time &next event

Adaptiveoptimum start


Space air temperature

Preheat

HVACapplications

Combined

Occupancy


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Operation

Operation of the adaptive optimum start optimiser is shown in Figure 2 and it can be described in threeparts

Calculated start time Outside temperature correction Adaption factor

Calculated start timeThe optimiser uses the boost constant (default 20 min / K) to calculate the duration of the preheatperiod and this is based upon the delta T (T) value between the current space temperature and thedesired space temperature (default 21C) required at the start of occupancy. This calculation will onlytake place as long as the following conditions are satisfied

The optimiser is not in a preheat mode

The current space temperature is lower than the desired space temperature at occupancy The outside temperature is less than 15C

Figure 2: Adaptive optimum start optimiser operation

C

06:00

21

space temperaturemax. preheat duration

occupancy start

desired spacetemp. atoccupancy

22:00

normal operationpreheat

calculated start time

03:00

12

space temp.

desired spacetemp. correctionfactor

outside temperature

C

10

(10*0.1)=1

1

0

0 20

K

time to raise 1kelvin

space temp.

Boost constant

minutes

16:00

occupancy end

Preheat

Occupancy

CombinedBooleansignals

t

oHVAC

ap

plications


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The calculated start time may also be adjusted by the outside temperature correction algorithm andadaption factor. The preheat period will be no longer than the maximum preheat time parameter

(default 8hr)

Outside temperature correctionThe outside temperature is used to adjust the desired space temperature at occupancy and thereby thepreheat period to avoid undershoot and overshoot during the spring and autumn seasons. The productof the outside temperature and the desired space temperature correction factor (default 0.10) issubtracted from the desired space temperature. This provides a corrected desired space temperaturevalue which is then used to calculate the preheat period

Adaption factorThe adaption factor (default 0.8) is a measure of learning within the optimiser because it reflects howsuccessful the optimiser was at the end of the preheat period. It is used to correct the next calculatedstart time.

If the desired space temperature at occupancy is achieved then there is no change to the adaptionfactor. This value will be used for the subsequent occupancy period

If the desired space temperature is achieved early then the adaption factor will be adjusted to alower value so that the subsequent occupancy period will start later

If occupancy time occurs before the desired space temperature is reached then the adaption factorwill be adjusted to a higher value so that the subsequent occupancy period will start earlier

In the example shown in Figure 2, the space temperature is currently 11C. The desired spacetemperature at occupancy of 21C is corrected to 20C due to the outside air temperature and desiredspace temperature correction factor (10*0.1=1). This means that the heating plant must raise the space by9C which will take 3 hours (with a boost constant of 20 minutes per 1K). If the desired space temperature

at occupancy is achieved then there will be no change to the adaption factor of 0.8.


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Non adaptive optimum start optimiser

Overview

Optimum start is used for the optimisation of start time for heating systems in intermittently occupiedbuildings with regular occupation profiles. Optimum start control systems are now required by manystatutory building regulatory bodies. For example, in the UK, optimum start is required for heating systemsof over 100kW capacity and generally recommended for heating systems of over 30kW capacity.

In a heating application the optimum start strategy will switch on some time before the time that peoplearrive in the building, in order to heat the building up to its normal occupied temperature. This is known asthe preheat period. How long the preheat period needs to be depends on the outside temperature and thethermal response time of the building structure. An optimum start strategy monitors the outsidetemperature, and ensures that the preheat period is the correct length of time for the building to reachoccupancy temperature neither before nor after people arrive. This minimises energy wastage by'optimising' the preheat time.

The optimum start function that is used in Vykon HVAC two variants, adaptive and non-adaptive and bothare used extensively in the Vykon HVAC applications. Three boolean signals are provided by the optimiserfor use by other HVAC applications. These are; Preheat, Occupancy and Combined. Figure 1 shows asummary of the Vykon HVAC non adaptive optimum start optimiser.

Operation

The non adaptive optimum start optimiser does not use the space temperature in its calculation of starttime. It relies entirely on the outside temperature only and it calculates the start of preheat from the outsidetemperature and a factor which reflects the performance of the heating plant and building fabric. Operationof the non adaptive optimum start optimiser is shown in Figure 2.

Figure 1: Non adaptive optimum start optimiser

Time &next event Non adaptive

optimum startOutside air temperature

Preheat

HVACapplications

Combined

Occupancy


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Calculated start time

The start time of preheat is calculated by using a delta T (T) value between the outside temperatureand a 15C constant. The calculated preheat time is the product of this T value and a degree hourfactor (default 0.25) and this is a cumulative algorithm. This calculation will only take place as long asthe following conditions are satisfied

The optimiser is not in a preheat mode The outside temperature is less than 15C

The preheat period will be no longer than the maximum preheat duration parameter (default 8hr). Inaddition, if the preheat period follows a period of extended shutdown such as a holiday, then thepreheat period will be extended by the value of the extend preheat after holiday shutdown value(default 10 minutes).

Figure 2: non adaptive optimum start optimiser operation

06:00

max. preheat duration

22:00

normal operationpreheat

calculated start time

03:00

space temp.

preheat time = 15 C outside temperature * degree hour factor

Outsidetem

erature C

occupancy start

16:00

occupancy end

Preheat

Occupancy

CombinedBooleansignals

toHVAC

applications


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Setpoint change delay

Overview

The setpoint change delay function provides a method of smoothly changing a setting from one value toanother. When a setting is subjected to a sudden and violent step change the resulting control strategymay become unstable while it reacts to the new setting. A typical example is where the setpoint to a controlloop is changed from one value to another when the system moves between normal and night setbackoperation. By introducing a setpoint change delay the step change can be made to incrementally movebetween settings thereby smoothing out any sudden change.

The setpoint change delay function, referred to in the Vykon HVAC applications is provided by a decreasevalue function. This function is designed to be a universal control device that can be used for any type ofapplication which requires a delayed change between two values.

Operation

The output of the decrease value function will be set equal to the input when the enable signal is true.When enable goes false then the output will decrement towards zero at a rate determined by the interval,which has a default of 10 seconds, and a step value of default 0.1. This fundamental relationship is simplydescribed in Figure 1.

-IN

EnableTrue

False

interval

Figure 1: Decrease value operation

+IN

0

(setpoint change delay)

step value

(0.1)

output


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When the decrease value function is used as a setpoint change function then the setpoint will change to thenew value at a rate determined by the configurable setpoint change delay parameter and a step value of0.1. In the example shown in Figure 2, the control loop setpoint will be changed smoothly over a period of 5

/ 0.1 seconds. This equates to a delay of 50 seconds.

Figure 2: Typical decrease value operation

1 sec

50

45

setpoint change delayC

controlloopsetpoint

normal operation night control

step value0.1

delay


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Application Status

Overview

The main graphic view of every one of the Vykon HVAC applications contains a Status label which can beused to manually override the application. In addition it contains a Status log which details the recenthistory of the applications status.

Operation

There are two functions available by mouse click on the status label of the main graphic view of eachapplication and these are illustrated in Figure 1

Status label Left mouse click:A pop-up dialogue displays the contents of a status (string) log which by default shows the most recent

30 records of automatic and manual events of the application status. The Time range drop-downallows for a different range filter to be selected. The list may also be exported by use of the columnselection switch

Status label Right mouse click:The application may be manually overridden to On / Off / Auto. Note that this manual action will notoverride any safety interlocks such as frost protection that may be configured or in operation.

Figure 1: Status label operation


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General functions and applications

All the applications which make up the general applications can be inspected and used by the applicationsengineer by accessing them via the hvacAppsGeneral module in the palette. There are also a number ofgeneral functions included in this which can also be configured and set. General applications (GeneralApp)is a super-application but breaks the rule of being available for selection in the New HVAC station wizard.This is because it is always automatically selected and available in every station because it is part of thedefault station which is used whenever the wizard creates a station. General functions and applicationsconsist of some general station application configuration and setup and the following functions andgeneral applications will be detailed in this section:

General functions

Pump exercise Alarms

General applications

Holiday schedule application Time schedule application Outside temperature application Average outside air temperature application Night purge application Fire override application Trace heating application


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The pump exercise application

Overview

Whenever mechanical devices such as pumps are not used for long periods of time, seizure due tocorrosion and precipitate build-up may occur. Pump exercise is an application which exercises the pumpsperiodically to ensure operation after the times of inactivity.

The pump exercise application can be found in the hvacAppsGeneral module. It is also one of a number ofapplications that are part of the GeneralApp which is a super application and is part of the default stationand automatically installed in every Vykon HVAC station database. It provides a pump exercise strategywhich can be used by other super applications. Figure 1 summarises the pump exercise application

Pump exerciseapplication

HVACapplications

Figure 1: The pump exercise application

On / OffTime &day

Enable pumpexercise

Direct

None

Interval


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Control strategy

There are two methods of pump exercise available within this application; Direct or Interval. Thedifference between the two relates to the flexibility required for pump exercise, particularly on whether

individual pumps have differing requirements for their pump exercise operation:

Direct:An example of pump exercise (direct) is illustrated in Figure 2. This is the simplest method of operationand is selected when the Enable pump exercise is configured as Direct. A Day of week is set toselect the day(s) during the week when the pump exercise must occur. The Start time and End timesettings determine when on the day(s) the pump(s) will start and stop under control of this pumpexercise application. A pump exercise configuration within every relevant HVAC application must alsobe set to Direct thereby providing a consistent site-wide Direct pump exercise strategy.

Figure 2: Pump exercise (Direct) operation

Direct(General app)

Time

S S M T W T F S S M T

Direct

(HVAC app)

Pump


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Interval:An example of pump exercise (interval) is illustrated in Figure 3. This method gives some control ofwhen the pump exercise occurs to individual pumps in the relevant HVAC applications and also is

dependent upon the normal operation of the pump. If the pump has been running normally then apump exercise is not required. It is only after the pump has not been running for some time (theinterval) then a pump exercise is needed but furthermore, this pump exercise may be scheduled not torun at inconvenient times during the week such as when there are no maintenance personnel on site.

This method of pump exercise is selected when the Enable pump exercise is configured as Interval.The Day of week, Start time and End time settings determine an operational window during theweek when the pumps may perform a pump exercise operation. The exact time and duration of thepump exercise is determined by the settings within each relevant HVAC application and the normaloperation of each pump but this pump exercise application effectively gives an enabling operationwindow.

This method will allow pump exercise to occur for example only at times when the maintenance facility

is on-site such as during a weekday. It also allows individual pumps to have different regimes for thefrequency that pump exercise takes place and for how long it lasts. The pump exercise configurationwithin every relevant HVAC application must therefore be set to Interval. When this is done the Pumpexercise interval and the normal running of the pump sets the frequency of pump exercise and thePump exercise duration sets how long it lasts. Note that the interval timer in the HVAC application isreset whilst the pump is normally running and the reset removed every time it stops.

Figure 3: Pump exercise (Interval) operation

S M T W T F S S M T W T

Time

Interval(General app)

Interval(HVAC app)

Pump

Reset removed


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Note that only when the Pump exercise interval has expired and the pump exercise application Starttime is active the pump will start and this is illustrated by the example in Figure 4.

Finally, beware that if the pump exercise application is set to interval with Start time and End timesset appropriately large but if the relevant HVAC application is set to direct, the pump will operate forthe duration of the start-to-stop time.

Figure 4: Pump exercise (Interval) operation

S M T W T F S S M T W T

Time

Interval(General app)

Interval

(HVAC app)

Pump


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Alarms

Overview

All the super applications of Vykon HVAC contain strategy options that include the allocation of one or morealarms which alert users, of any mechanical plant failure or adverse environmental conditions. Thesealarms are collected in two alarm databases called Urgent alarms and NonUrgent alarms. The alarmsare available for review and acknowledgement via the browser interface. In addition, the alarms in thesedatabases can be made to affect the condition of one or more visual or audible indicator devices whichcould be sited in the mechanical plant room or elsewhere in the building under control.

Alarm classification and behaviour

There are two main alarm databases that contain the alarms which alert users of any mechanical plantfailure or adverse environmental conditions. These are

Urgent Alarms Non Urgent Alarms

The behaviour of each is similar with respect to annunciation or indication and acknowledgement but thesetwo provide a priority choice to offer some categorisation of alarms. A HighHigh alarm which is monitoringa boiler flow high temperature is an example of an Urgent Alarm but a High alarm which is monitoring thesame boiler flow temperature but configured at a lower level to give a warning is an example of a NonUrgent Alarm.

Vykon HVAC has another two types of alarm classification for the alarms in each of these two databases.These are

Urgent Alarms Ack and Urgent Alarms NoAck Non Urgent Alarms Ack and Non Urgent Alarms NoAck


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The significance of the Ack and NoAck types, as their names suggest, relates to options on the behaviourof the alarm and plant control with respect to Acknowledgement. Consider the boiler application exampleillustrated in Figure 1 to describe the operation of the Ack and NoAck functionality

Using the signals shown in Figure 1, consider the following operation1) A boiler goes into lockout and raises a boiler failure alarm2) The boiler immediately becomes unavailable for demand and sequence control3) The alarm indicator, which may be sited in the plant room, goes to an active on state4) An (as yet) unacknowledged alarm is raised

5) If the alarm is of the Ack type then, even though the original boiler failure alarm clears, the boiler stillremains unavailable until an Acknowledgement is generated either from user acknowledgement viathe browser interface or from pressing the Reset pushbutton

6) Alternatively, if the alarm is of the NoAck type then, even though an acknowledgement has not beengenerated, as soon as the original boiler failure alarm clears the boiler becomes immediately available

Notes: If an acknowledgement of an (as yet) uncleared alarm is generated then both Ack and NoAck types

behave in exactly the same way in that there is no change of I/O condition The behaviour of the Alarm indicator(s) when an acknowledgement is generated when the alarm is

still active can either be to go off or to remain on until all the alarms are cleared. This is set by theAlarm indicator behaviour setting

Figure 1: Alarm Ack and NoAck behaviour

Boiler failure alarmFail

Normal

Boiler availabilityAvailable

Unavailable

Alarm indicator(s)On

Off

Browser interface viewNo alarm

Alarm

Acknowledge

UrgentAlarmsAck and NonUrgentAlarmsAck behaviour:

Boiler failure alarmFail

Normal

Boiler availabilityAvailable

Unavailable

Alarm indicator(s)On

Off

Browser interface viewNo alarm

Alarm

Acknowledge

UrgentAlarmsNoAck and NonUrgentAlarmsNoAck behaviour:

No alarm visible

Unacknowledged alarm

Unacknowledged cleared alarm

Acknowledged uncleared alarm

Alarm indicator behaviour


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Alarm indicator strategy

The alarm indicator strategy contains the following main features

Reset pushbutton One or two alarm indicators Manual indicator

An optional reset pushbutton, usually sited alongside the indicator device, can provide a manual feedbackto reset the alarm indicators. The current state of all the indicators and the reset pushbutton is available inan overview graphic. Please note that the name shown in the overview is the name of the mapped I/Odevice.

A similar facility of a local plant room or building indicator device exists for the manual mode condition ofthe I/O module channels. There are two varieties of manual mode that the I/O channels can be in.Mechanical plant can be manually overridden either through the browser graphical controls, by using theTrue or False selection, or by using the hand-off-auto bypass switches that exist on the digital output and

analogue output channels of some of the Vykon HVAC I/O modules. It is important that users are alerted tothe condition of all the plant with relation to manual override because this will cause a loss of efficiency ifleft in a manual mode. An indicator device output which again, could be sited in the mechanical plant roomor elsewhere in the building under control, is available such that it will be active if any I/O channel is in amanual mode. The overall alarm indicator strategy is illustrated in Figure 2.

Figure 2: Alarm indicator strategy

I/O module override

switch status

Resetpushbutton

Urgent alarmindicator

Externalsignals

Acknowledge

I/O channel manualoverride

NonUrgent alarms(Ack or NoAck)

Urgent alarms(Ack or NoAck)

Acknowledge

1 or 2indicators

NonUrgentalarm indicator

Indicatordriver

Manual?

Manualindicator

Off after reset Off after allalarms cleared

Alarm indicator behaviour


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When pressed, the reset pushbutton automatically acknowledges all the alarms in both the Urgent andNonUrgent alarm databases. Whether this reset action also switches the indicator(s) off or whether theindicator(s) remain on until all the active alarms have cleared is determined by the alarm indicator

behaviour selection. There are two settings for this selection and the behaviour of each is describedhere

Off after reset: The indicator will go off after the reset pushbutton has been pressed despite thealarm being still in an active state. By using this setting it can be clearly identified in the plant room thatif an alarm from another source occurs then the indicator will return to an on condition to highlight thatanother problem has arisen

Off after all alarms cleared: The indicator will only go off when all the active alarms have beencleared. This is also a very useful and simple indication to signify that there are no more alarms activein the system (this is the default setting)

Finally, if only one indicator, (it must be the Urgent alarm indicator), is mapped then the strategyautomatically allocates the single indicator behaviour to both databases.


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The holiday schedule application

Overview

A holiday schedule enables a number of preset time periods to be configured throughout a calendar yearwhich affects the way that a site installation may operate as regard to occupancy. The holiday scheduleapplication is mainly used as an optional override for time schedule applications but it may also be useddirectly in some hvac applications.

The holiday schedule application can be found in the hvacAppsGeneral module. It is also one of a numberof applications that are part of the GeneralApp which is a super application and is part of the default stationand automatically installed in every Vykon HVAC station database. It provides a holiday schedule strategywhich can be used by other applications. Figure 1 summarises the holiday schedule application:

Control strategy

Output from the holiday schedule application to the time schedule and hvac applications is an off condition

unless the current time and date corresponds with its settings for an event holiday in which case an oncondition is given. The effect of the holiday schedule override on a time schedule is that if the holidayschedule is active then the time schedule will be overridden to an off condition. Figure 2 illustrates atypical example.

Holiday scheduleapplication

Time scheduleand HVACapplications

Figure 1: The holiday schedule application

on / offTime &

date

Figure 2: The holiday schedule


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Up to four holiday schedules may be created and each one has the following controls and configurationoptions which are illustrated in Figure 3:

Name:Each holiday schedule must have a unique name allocated to it. This is used to identify it when theholiday schedule is linked to other applications

Independence:Up to four holiday schedules (Holiday schedules 1, 2, 3 and 4) may be created; However they areindependent of each other and can be individually deleted when not required without affecting the otherschedules. This is illustrated by schedules 1 and 3

Event range:Up to 10 independent events or ranges may be created in any one holiday schedule. Each event maybe either a Single day event in which case only a start date is configured, or a Date range where botha start and end date are configured

Event description:Each event may have an Event description to describe the event

Each year:Each event may be configured to repeat Each year or be regarded as a one-off event

Auto delete expired dates:Each holiday schedule may be configured to automatically delete any event which has not beenselected to repeat Each year and whose date has expired

Manual override:The current state of the holiday schedule may be overridden manually by right mouse click on the

current status


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Figure 3: Holiday schedule controls, configuration and event creation


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The time schedule application

Overview

Fundamentally, a time schedule enables a number of on and off times to be preset within a weekly period.These are times that represent for example the occupancy of a building, floor or zone, or which may enablethe switching of lights within an exhibition hall. The Vykon HVAC time schedule application has a numberof extra features that can be added to its basic functionality. These are; holiday schedule influence,optimisation, time extension and setpoint. Up to 16 independently operating time schedule applicationsmay be configured.

The time schedule application can be found in the hvacAppsGeneral module. It is also one of a number ofapplications that are part of the GeneralApp which is a super application and is part of the default stationand automatically installed in every Vykon HVAC station database. It provides a time schedule strategywhich can be used by HVAC applications. Figure 1 summarises the time schedule application

Holiday schedule

HVACapplications

Figure 1: The time schedule application

Current stateTime &da

Next event/value

Time extension

Time scheduleapplication


Space air temperature

Time extension


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Control strategy

Output from the time schedule application to the HVAC applications is an off condition unless the currenttime corresponds with its schedule settings in which case an on condition is given. Figure 2 illustrates a

typical example showing the users view of the schedule.

Up to sixteen time schedules may be created and each one has the following controls and configurationoptions which are illustrated in Figure 3:

Name:Each time schedule must have a unique name allocated to it. This is used to identify it when the timeschedule is linked to other applications

Independence:Up to sixteen time schedules (Time schedules 1, 2, 3 thro 16) may be created; However they areindependent of each other and can be individually deleted when not required without affecting the otherschedules. This is illustrated by schedules 1, 2 and 4

Period range:Up to 4 periods or ranges may be created in any one day of a time schedule. In addition an All dayperiod may be configured in which case the schedule is on for all 24 hours.

Figure 2: The time schedule


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Figure 3: Time schedule controls, configuration, period creation and adjustment


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Manual override:The current state of the time schedule may be overridden manually by right mouse click on the currentstatus and this is illustrated in Figure 3

Time extension:Up to 6 external digital input signals (5 continuous and 1 pulse) may be linked to a time schedule togive a pre-defined extension time, which has a default value of 1 hour. This provides an externalmeans of extending the on time of the schedule or, if it is not already on then switching it on. Inaddition a manual start extension override is provided. Figure 4 shows an example.

If the time extension signal is derived from a pulse status input then there is an additional overrideoption whereby the pulse signal can force an immediate extension time or, if the schedule is already on,the extension time will not start until the end of the current on period. This is illustrated in Figure 5

Holiday override:A holiday schedule application may be configured to override the time schedule. The holiday scheduleapplication is described elsewhere in this document. There are a number of settings which are specificto the holiday schedule override influence and these are illustrated in Figure 6

Figure 5: Time extension (pulse only)

Figure 4: Time extension

Figure 6: Holiday schedule influence


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Holiday schedule influence: This setting simply defines whether the linked holiday schedule will haveany influence, or override (Yes) on the time schedule or not (No)

Holiday schedule action: If the linked holiday schedule does have influence on the time schedule,then is the override action to take place throughout the whole week (Always) or is the override actionrestricted to a preset period in the week (Period)

Weekly period: If the holiday schedule override is restricted to a period during the week, then whattime (from / to) is it active and does that also include weekends (Active on weekends) or not (Inactiveon weekends)

Optimiser selection:A time schedule application may optionally be configured to operate as either an adaptive optimiser,using outside and controlled space air temperature, or non-adaptive optimiser, using only the outside

air temperature. The time schedule application can thereafter be regarded and used by other HVACapplications as an optimiser schedule. The functionality of adaptive and non-adaptive optimisation,applicable to the time schedule, is described elsewhere in this document. The default start condition ofa time schedule application is None, without optimisation

Setpoint (numeric):A time schedule application normally by default operates with a boolean On / Off output. However thetime schedule may optionally be configured to provide a numeric setpoint during its On condition. TheOn condition setpoint value is adjusted from the period adjustment dialogue and the Off conditionsetpoint value is adjusted via the settings button and this is illustrated in Figure 7

Figure 7: Setpoint (numeric)


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Setpoint (off / low / high):A time schedule application normally by default operates with a boolean On / Off output. However thetime schedule may optionally be configured to provide an off / low / high setpoint during its On

condition. The On condition setpoint value is adjusted from the period adjustment dialogue and theOff condition setpoint value is adjusted via the settings button and this is illustrated in Figure 8

Temporary disable:For some HVAC applications such as for example a school premises, it is sometimes necessary to

temporarily disable the time schedule when for example the school is unusually closed for a shortholiday and this could occur for up to 3 days. A temporary disable feature is available in the timeschedule settings which allows for the schedule to be disabled for off (none) one, two or three days andthis is illustrated in Figure 9

Figure 8: Setpoint (low/high)

Figure 9: Temporary disable


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The outside temperature application

Overview

HVAC applications such as those that control air and heating systems require interlock signals to changetheir mode of operation during conditions of low or high outside air temperature. Operation during theseconditions is often described as frost protection and summer/winter mode. The outside temperatureapplication provides three interlock signals which are based upon the outside air temperature and time.The outside temperature application can be found in the hvacAppsGeneral module and up to four may beconfigured in a station. It is also one of a number of applications that are part of the GeneralApp which is asuper application and is part of the default station and automatically installed in every Vykon HVAC stationdatabase. Figure 1 summarises the outside temperature application:

Control strategy

Up to four outside temperature applications may be created and each one has the following controls andconfiguration options which are illustrated in Figure 2:

Name:Each outside temperature application must have a unique name allocated to it. This is used to identifyit when the application is linked to other applications. Note that the name is automatically given to theapplication and is the same name as the outside air temperature sensor to which it is linked


HVAC

applications

Figure 1: The outside temperature application

Frost limitTime

Summer condition

Summer stop

Outside

temperatureapplication

Figure 2: Outside temperature configuration and options


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Independence:Up to four outside temperature applications (outside temperature 1, 2, 3 and 4) may be created.However they are independent of each other and can be individually deleted when not required without

affecting the other outside temperature applications. This is illustrated by applications 1 and 4

Logging:The logging history record can be viewed as illustrated in Figure 3

The Vykon HVAC outside temperature application also contains three discrete condition strategies andprovides these as individually selectable and independent interlock signals for use by HVAC applications.The three conditions are described as follows and Figure 4 summarises the operation of all three:

Frost limit:To indicate a condition of low outside air temperature, a Frost limit condition interlock signal isgenerated. This signal is independent of real date and time and will switch to an on condition if theoutside air temperature falls below a preset value. The condition is protected against instability whichcan be caused by small fluctuations in outside temperature by virtue of an adjustable time basedhysteresis control. This ensures that the measured outside air temperature has to change by asignificant amount and be stable over a time period before a switch to the frost limit condition is made.The default settings of frost limit on and off are 5C and 6C respectively. Typical use of this interlock is

the starting of circulation pumps and the enabling of heating systems

Figure 3: Outside temperature logging


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Summer condition:To indicate a condition of high outside air temperature such as that experienced during the early to latesummer seasonal period, a Summer condition interlock signal is generated. This signal isindependent of real date and time and will switch to an on condition if the outside air temperature risesabove a preset value. The condition is protected against instability which can be caused by smallfluctuations in outside temperature by virtue of an adjustable time based hysteresis control. Thisensures that the measured outside air temperature has to change by a significant amount and bestable over a time period before a switch to the summer condition is made. The default settings ofsummer condition on and off are 21C and 18C respectively. Typical use of this interlock is thedisablement of heat demand signals from room radiator control systems.

Summer stop:To indicate that a condition of an extended duration of high outside air temperature exists such as that

experienced during the mid-summer seasonal period, a Summer stop condition interlock signal isgenerated. This signal is different from the other two in that its output is adaptive and based on what

C

Outside

airtemp.

late spring day

Figure 4: Outside air temperature condition strategy

early summer day mid summer day late summer day

9 16

Frost limitOn

Off

56

17

Summercondition

On

Off

Summerstop

OnOff

18

21

916

916

916

summer stopenable delay

start timesummer

stop disable

summer

condition

Off

On

OnOff

frost

limit

outside temp.disable summer

stop

end timesummer

stop disable


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outside air temperature conditions were experienced on the previous day. Once it is set on, thesummer stop condition can only be reset off when the outside air temperature falls below a preset valueduring the day between mid-morning and mid-afternoon. A typical use of this interlock is within an

energy saving strategy to prevent the unnecessary generation of heat to satisfy room radiator systemdemand during the early morning and late afternoon. This would be a waste of energy because fromthe experience of the previous day the likely rise in outside air temperature would then cause anincreased demand from the cooling systems. The summer stop condition can only asserted after thesummer condition has been on for an uninterrupted period (the default is 2 hours). The summer stopcondition is only reset when the outside air temperature falls below a preset value (the default is 17C)during a time period (the default is a 7 h

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