Tynetec Advent xt - Final System Test and Support Contact

DocNo.FM0410issueM‐1Page9
5.NETWORKLOADCONSIDERATIONS
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Itisveryimportanttotakevoltagedropacrossthesystemnetworkintoconsiderationwhenplanninganinstallation.Itis
thecableresistanceonthepowersupplywiringthatgivesrisetovoltagedrop‐thelongerthecablerunandthelargerthe
currentrequirement,thelargerthevoltagedrop.
Toperformadetailedassessmentofvoltagedropiscomplex;youneed
toknowthecurrentrequirementofeachdevice,thedistancebetweeneachdeviceandtheresistanceofthecableper
metre.Toestimatetheworstcasescenariosimplytakethemaximumcablerunandcalculatethevoltagedropasifall
deviceswereattheendofthecable.
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TypicalcurrentrequirementsofdevicesconnectedtotheAdventxtnetworkaregivenbelow:
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24VNetworkDevices Standby Active
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StandardIntercomUnit 2mA 10mA
RemoteIntercomUnit 2mA 10mA
CeilingPullcordwith24VLED 0mA 10mA
DoorEntryTelephone 3mA 15mA
DoorEntryTelephonewithLEDon 4.5mA N/A
CombinedIntercom 2mA 70mA
CombinedIntercomwithLEDon 7.5mA N/A
Manager/LiftCallpoint 2mA 10mA
NetworkReceiver 10mA 10mA
StatusModule 12mA 12mA
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12VAuxiliaryDevices Standby Active 
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DigitalDoorPanel 30mA 250mA
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EXAMPLE
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Theestimatedvoltagedroponaninstallationwith40intercoms,1statusmodule,1managercallpoint,1liftcallpointand6
networkreceiverson400metresofcablewouldbe;
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 (40x2mA)+(1x12mA)+(2x2mA)+(6x10mA)=totalcurrent156mA(0.156A)on24Vline
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 400metresofCW1308cable=40Ω(10Ωper100metres)
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 usingV=IxR:0.156Ax40Ω=6.24Vdropon24Vline(leavingapprox.18V)
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Devicesonthe24Vsupplywillworkdowntoapprox.16Vthereforetheabove dropisacceptable.
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REDUCING VOLTAGE DROP
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Thereareseveralmeansofreducingthevoltagedrop;siteconditionswilldictatewhichisused;
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1.Thebestsolutionistosplitthenetworkintoanumberofshortspursratherthanonelongrun.Thishastheadvantageof
smallervoltagedropspercablerunandsimplifiedfaultfinding. 
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2.Onlargeinstallationsinstalla1.0mmpowerpairoraCW1308withadditionalsparepairstoallow“doubling‐up”on
powerconductors.Increasingthecablecrosssectionareawillreduceitsresistancethereforereducingtheamountof
voltagedropped.
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3.Loopingbackthepowerconductorsfromthelastintercomtothecontrollerwillformaringcircuitwhichwilleffectively
halvetheresistance.
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4.Anauxiliarypowersupplycanbeconnectedtothesitewiringatasuitablepointto“jack‐up”thesupplymidwayalong
thecablerun.Thedisadvantageofthisbeingfuture serviceengineersmaynotbeawareofPSU’spresenceandthe
networkwillremainpoweredwhenthecontrollerisswitchedoff.
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THERESISTANCEOFCW1308CABLEIS
APPROX100ΩPER1000METRES