? Combiner & Breaker's

tcvb

If panels are wired in parralell,say three 135 watt panels. When you wire them into the combiner does the breaker go on each panel and what does the breaker look at the feeder going to the charger?Another question when you install the breaker in the combiner each panel has it's own breaker now how does that work as far as the feeder goes?

Still learning and researching and dabbling in this,:)

Thank's

crewzer

Re: ? Combiner & Breaker's

Not quite sure I understand your question(s), but here we go:

Module voltage (or, if several modules are wired in series, string voltage) is defined by National Electrical Code (NEC) Article 690.7. It's basically STC Voc times the "local record low" temperature correction factor. See: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/HP129_PV%20MATH_Code_Corner.pdf

Module current (or string current) is defined by NEC Article 690.8(A)(1). For NEC purposes, a module's source current is considered to be 125% of the STC Isc. Assuming using a DC-rated circuit breaker (not an AC-rated breaker) rated for 100% continuous duty, the breaker rating would be 125% of the module's STC Isc, rounded up to the next standard value.

Wiring identical modules (or strings) in parallel may or may not require overcurrent protection devices. See: http://www.nmsu.edu/~tdi/pdf-resources/CC125.pdf

The PV array's total output current is the sum of the currents described above. The circuit breaker must be rated for this current spec. See: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/HP130_pg114_CodeCorner.pdf

HTH,
Jim / crewzer

audredger

Re: ? Combiner & Breaker's

Crewzer is correct but, I read your question slightly differently???
3 135 watt panels in parellel.... The negative wire (-) from each panel goes to the bus bar in the combiner box, the positive wire (+) goes to the fuse / breaker in the combiner box. The fuse/breaker should match the rating on the pv module data plate. The paralleling happens on the output side the fuse/ breaker.

The wires/cable from the combiner box go to where the charge controller is and then there is another fuse/breaker. The size of this fuse/breaker is the sum of the fuses/breakers at the combiner box. Then into the charge controller.

The charge controller has another fuse/breaker on the output side and it is generally the max output of the controller.

Example: If the data plate on the solar panel says "max series fuse 5 A" and, you are using a 40 Amp charge controller. Then you would have three 5 amp fuses/breakers in the combiner box. A 15 amp fuse/breaker just before the charge controller and a 40 amp fuse/breaker on the output side of the charge controller.

One thing you didn't mention was a lightning arrestor, http://store.solar-electric.com/deldcphotsur.html , there should be one of these at the combiner box and one at the DC breaker box.

crewzer

Re: ? Combiner & Breaker's

I don't agree with merely following the PV module label's fuse rating. Let's consider the Kyocera KD135GX-LPU, a 135 W STC module with an STC Isc of 8.37 A, and a fuse spec of 15 A.

NEC 690.8 says the maximum module current would be 8.37 A x 125% = 10.5 A. When using a DC-rated circuit breaker rated for 100% continuous duty (i.e. CBI from MidNite or OutBack), the next readily-available standard size up CB is 12 A.

CB's not rated for 100% continuous duty and fuses require a 125% safety multiplier. 8.37 A Isc x 125% x 125% = 13.1 A, so the next-size-up CB or 15 A fuse suggested by Kyocera would be appropriate.

Combining three of these modules in parallel would result in an NEC array current of 8.37 A Isc x 125% x 3 = 31.4 A. When using a DC-rated circuit breaker rated for 100% continuous duty (i.e. CBI from MidNite or OutBack), the next readily-available standard size up CB is 40 A.

CB's not rated for 100% continuous duty and fuses require a 125% safety multiplier. 8.37 A Isc x 125% x 125% x 3 = 39.3 A, so the next-size-up 40 A CB or fuse would be appropriate for OCPD'ing the array between the combiner box and the CC.

However, a 15 A x 3 = 45 A (or larger) CB or fuse would not.

HTH,
Jim / crewzer

audredger

Re: ? Combiner & Breaker's

You have a good point and, I agree.
In one of your previous links, the article spoke of listed series fuses being larger than NEC allows and that became a UL issue. Might this be on of those examples?

tcvb

Re: ? Combiner & Breaker's

crewzer wrote: »

Not quite sure I understand your question(s), but here we go:

Module voltage (or, if several modules are wired in series, string voltage) is defined by National Electrical Code (NEC) Article 690.7. It's basically STC Voc times the "local record low" temperature correction factor. See: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/HP129_PV%20MATH_Code_Corner.pdf

Module current (or string current) is defined by NEC Article 690.8(A)(1). For NEC purposes, a module's source current is considered to be 125% of the STC Isc. Assuming using a DC-rated circuit breaker (not an AC-rated breaker) rated for 100% continuous duty, the breaker rating would be 125% of the module's STC Isc, rounded up to the next standard value.

Wiring identical modules (or strings) in parallel may or may not require overcurrent protection devices. See: http://www.nmsu.edu/~tdi/pdf-resources/CC125.pdf

The PV array's total output current is the sum of the currents described above. The circuit breaker must be rated for this current spec. See: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/HP130_pg114_CodeCorner.pdf

HTH,
Jim / crewzer

OK,

When you bring the feed from the PV into the breaker it slips on the bus.Ok is this breaker looking at the feeder going to the Charger?And if so,what if other breakers are hooked into that same bus looking at that feeder?

crewzer

Re: ? Combiner & Breaker's

I'm sorry, but I really don't understand your question.


Jim / crewzer

BB.

Re: ? Combiner & Breaker's

[FONT=Fixedsys]
       +[/FONT][FONT=Fixedsys]--[series solar panel string 1]--:~:--+
[/FONT][FONT=Fixedsys]       +[/FONT][FONT=Fixedsys]--[series solar panel string 2]--:~:--+
[/FONT][FONT=Fixedsys](-)====+--[series solar panel string 3]--:~:--+====[+]
               paralleled             fuse/breaker[/FONT]s

So--just a quick ASCII drawing (Remember those)... The +/- go to the charge controller.

The +/+/+ are common points (bus connections).

[~] fuse/breaker per string.

You may need another breaker for the main run back to the solar charge controller if the Solar Array Imp*1.25 is greater than the current capability of the cable to the controller, or if the Imp*1.25 is greater than the controller's input current rating (typically Input = Output current rating).

-Bill