InstallationofPLCCores
22ndMarch2017,v1.11
Thisdocumentreferstothe
followingpartnumbers:
• PLC-CORE-57-1
• PLC-CORE-75-1
Eachpartnumbercontains
quantity1PLCCore.Theseitems
aresuppliedasanordering
convenience,andarealso
availabledirectlyfromthe
manufacturer:
http://www.coolblue-mhw.com
Purpose
OccasionallyPVinstallsusing
TrueStringinvertersexperience
issueswiththePowerLine
Communication(PLC)usedto
communicatebetweenthe
invertersandtheHiQ
communicationgateway.One
reasonforthiscanbethatthe
nearbygridissufficientlylow
impedancethatthePLCsignal
‘leaksaway’andhasinsufficientstrengthremainingforpropercommunicationtooccur.Inthis
instancethePLCCoresprovideameansofincreasinggridimpedanceinthefrequencyband
usedbytheHiQsystemtoensuresufficientsignalremains.Externalnoisecanbeanothersource
ofissues.
Sizing
Twosizesareoffered,asshowninthephotographs.USQuartercoins(whicharearound1”
across)areincludedforscale.Thesizerequiredwilldependuponthesizeoftheinstall/
thicknessofwiresbeingaccommodated.Theinnerdiametersareasfollows:
• PLC-CORE-57-1:57mm(2.25”)
• PLC-CORE-75-1:75mm(3”)
Physicalwirediameterandinternaldiameterofthecorearetheoverridingcriteria.Notethat
coresaturationisnotanissue,duetothefactthatallthreepowerphasesarepassedthrough
HiQSolar,Inc.
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InstallationofPLCCores
22March2017
thecore,resultinginanetzerofluxwhenallthreephasecurrentsareequal.Inabalanced
system,thecoresonlyseefluxfromthecommunicationsignal,whichisverysmall.
Chapter9,Table5oftheNationalElectricalCode1givesinformationonwirecharacteristics
includingwirediameterwithdifferentinsulationtypes.Similarinformationisalsoavailable
elsewhere23.
Eachcorewillhavethreewiresrunningthroughit.Atranslationfromwirediametertothe
diameterofabundlemaybecalculatedusingthekfactor4.For3wires,k=2.16.Itisalsouseful
toleavea10%margintoensurethefitissuretowork.
• Asanexample,theouterdiameterofTHHNwire4/0is16.3mm.3wiresinabundlewill
have16.3x2.16=35.2mm;adding10%margingives39mm.Thisfitscomfortablyinside
thesmaller(57mminnerdiameter)Core.
• Similarly,a750MCMTHHNwirehasanouterdiameterof30mm.30mmxkof2.16x
110%=71mm,whichwillfitinsidethelarger(75mm)Core.
Installation
TheendobjectiveistoachieveanimpedancebarrierwiththeinvertersandGatewayonone
side,andthegridontheother,withthePLCCoresbetween.Anexampleisshownintheline
diagrambelowwheretheCoresareinstallednexttotheloadcenter.IfthereisamainPV
disconnect,thiscanalsobeaconvenientplacetosituatetheCores.
1
http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-andstandards?mode=code&code=70
2
http://www.buildmyowncabin.com/nec/nec2011_chap9_table5.html
https://www.encorewire.com/wp-content/uploads/EncoreWire-THHN-SSE.pdf
4
http://www.nationalwire.com/pdf/cat07_design_guideV10.pdf,bottomofpage7-1
3
HiQSolar,Inc.
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InstallationofPLCCores
Grid
HotPhases
PLCCores
LoadCenter
22March2017
PVSystem
HotPhases
N
TrueString
Inverter
N
TrueString
Inverter
N
Gateway
Neutral
1HotPhase
EquipmentGround
NotethatfortheCorestoachievethedesiredaffect,allthreehotphasesmustpassthroughthe
samecore(s),andtheNeutralandGroundMUSTNOT.Werecommendaminimumoftwocores
beused,althoughmoremaybeaddedifdesiredandthereissufficientphysicalspace.
Theseitemsmustbeusedwithintheirratings:
L1 L3
L2
• http://www.coolblue-mhw.com/wpcontent/uploads/2016/11/M-113-Rev-0203.pdf
• http://www.coolblue-mhw.com/wpcontent/uploads/2016/11/M-114-Rev-0303.pdf
Breakers
Adesignguideisavailablefromthemanufacturer:
Grid
• http://www.coolblue-mhw.com/wpN,
content/uploads/2014/09/CoolBLUEGND
Installation-Guide.pdf
PVArray,
connec0ontoGateway
HiQSolar,Inc.
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