PV8 Breaker Sizing

Discussion about the Power System PV Combiner (PSPV)

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UgashikBob
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My RE system: Hup Solar One SO-6-85-21 for 1055 amp/hrs @48VDC Two Trace 4048 SW Plus One Small Power Systems Dual Axis tracker w/16 BP590E panels for 1.44 Kw tied to RV Industries 3048 controller w/remote display. Fixed arrary of 4 53 watt Solerex panels tied to Trace C40 for .2Kw. 2 SWW W100 one roof mounted one on 80' LMWS tower. 3 303/403 roof mounted toys. Omnimeter
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PV8 Breaker Sizing

Post by UgashikBob » Thu Apr 01, 2010 5:44 am

Will have 3 two panel series strings of Sanyo 215 panels into a PV8 combiner box. ISC for the 215 Sanyo is 5.61 x 1.25 for a breaker rating of 7.0125. What size breaker is appropriate for each 2 panel series string?

The Sanyo panels come with MC connections and I will have to calculate physical location to determine MC cable lengths from the strings to the combiner box. I'm sure the cables are outdoor rated but would you recommend a conduit of some sort for extreme conditions like mine?

Kent Osterberg
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Re: PV8 Breaker Sizing

Post by Kent Osterberg » Thu Apr 01, 2010 8:47 am

Per NEC 690.8 the minimum wire ampacity and breaker size is Isc x 1.25 x 1.25 = 8.76 amps. The maximum breaker size is specified on the PV module label, 15 amps for the Sanyo 215 you are asking about. So a 10-amp breaker would be a a satisfactory choice. You are less likely to have nuisance trips if you use a 15-amp breaker. With three or more parallel strings of modules, you'll need a breaker or fuse in every string.

UgashikBob
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Joined: Wed Jul 26, 2006 4:37 pm
My RE system: Hup Solar One SO-6-85-21 for 1055 amp/hrs @48VDC Two Trace 4048 SW Plus One Small Power Systems Dual Axis tracker w/16 BP590E panels for 1.44 Kw tied to RV Industries 3048 controller w/remote display. Fixed arrary of 4 53 watt Solerex panels tied to Trace C40 for .2Kw. 2 SWW W100 one roof mounted one on 80' LMWS tower. 3 303/403 roof mounted toys. Omnimeter
Location: Outlet Lower Ugashik Lake Alaska

Re: PV8 Breaker Sizing

Post by UgashikBob » Thu Apr 01, 2010 9:34 am

Thank you for the info.

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tallgirl
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Re: PV8 Breaker Sizing

Post by tallgirl » Thu Apr 01, 2010 12:26 pm

UgashikBob wrote:The Sanyo panels come with MC connections and I will have to calculate physical location to determine MC cable lengths from the strings to the combiner box. I'm sure the cables are outdoor rated but would you recommend a conduit of some sort for extreme conditions like mine?
Kent answered the breaker question, I'll take this one ;)

The cabling is USE2, which is rated for outdoor and sunlight exposure. It is a much more cold tolerant insulation than THHN, which tends to be used to make connections from combiner boxes back to charge controllers. Conduit would be nice, but I'm not sure what is "extreme" about your conditions -- remember that conduit can have its own issues with condensation forming inside of it and causing rust or freezing or bugs or you name it. If precipitation is an issue, drip loops are a must, as well as drain holes and other such things. Keep all that in mind if you choose to go the conduit route.
Julie in Texas

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