Hi, I'm building my first solar kit. I know that too many amps going down a thin wire can melt the wire or destroy the mppt. I plan to run the 4 100w panels in series. I think that this will increase the voltage but that my mppt should keep it at 12v so that I can run 12v devices. I know that in series that amps DO increase. My question is what size circuit breaker should I use on the 4 to 1 combiner harness. Meaning...the 4 sets of wires coming from the panels into ONE wire that goes into the MPPT. I want to put a circuit breaker after the ONE wire harness before it goes into the MPPT. I have a 40 amp circuit breaker and a 50 amp circuit breaker. However what I'm reading is the series panels will keep the amps to a total of about 5.7 amps. So should I put in just a 10 amp circuit breaker or will that keep tripping? Any help appreciated! Thanks
100w x 4 panels / 12v in series. What size circuit breakers?
- Thread starter clyoul3ss
- Start date
In series you add the voltage and keep the amperage the same.
In parallel you add the amperage and keep the voltage the same.
If you really do intend to put the 4 panels in series then the amperage does NOT increase. The voltage increases. You do not need any fuses or breakers for a 4S arrangement.
If you actually intend to put your 4 panels in parallel (why?) then the amperage would be 4 times one panel and with 3 or more in parallel you need to fuse all of the parallel strings.
Independent of either arrangement, you might want a disconnect breaker on the PV wires near the SCC.
Post the full specs of your panels.
Post details about your SCC.
With that info people can offer the best suggestions.
In parallel you add the amperage and keep the voltage the same.
If you really do intend to put the 4 panels in series then the amperage does NOT increase. The voltage increases. You do not need any fuses or breakers for a 4S arrangement.
If you actually intend to put your 4 panels in parallel (why?) then the amperage would be 4 times one panel and with 3 or more in parallel you need to fuse all of the parallel strings.
Independent of either arrangement, you might want a disconnect breaker on the PV wires near the SCC.
Post the full specs of your panels.
Post details about your SCC.
With that info people can offer the best suggestions.
Thanks for the info Rmaddy. I'm pretty sure I'll be running them in series. So I guess i don't even need a 4 to 1 harness. I'll probably use one of the extra 50 amp circuit breakers I got to go between the battery and the 40amp SCC and use the 2nd one as a "disconnect breaker" on the PV wires near the SCC to turn the PV's off. Does that make more sense? I saw some videos where they did put fuses between the PV and the SCC I guess that's not needed every in series? or just small setups in series?
Doesn’t make sense. The wire you are using has a max rating of 30 amps. That’s what the Mc4 connectors are rated for. If you are running series you will only have about 5 or 6 amps at about 100 volts. I suggest a breaker around 25 amps used as a cutoff switch near the SCC. Be sure to fuse the wires at the battery regardless if you have a circuit breaker or not.
Check your SCC max voltage. Most likely the 4 panels will be close or over. Would be better to run 2S2P. That will put you into the 10amp at 50 volt range.
Check your SCC max voltage. Most likely the 4 panels will be close or over. Would be better to run 2S2P. That will put you into the 10amp at 50 volt range.
I connected it all up today 4 100w panels in series. It worked from what I can see. I think I did the circuit breakers wrong though. I'm running 6 awg from the SCC to the battery and thinking about taking STWs' advice and putting a 25amp breaker between the SCC and the battery. Although the charts I'm seeing say that 6 awg copper wire should be fused/circuit breaker around 70 amp. I do have a 50amp circuit breaker. Shouldn't I use that at least instead of a 25 amp? That way if the wires get too hot the circuit will break at 50 amps which is a lot closer than 25 amps.
As far as the circuit breaker between the PV and the SCC from what you said Rmaddy I don't need one if I'm running the PV in series...I am definitely running the PV in series. Since the PV will only be putting out around 6 amps......should I put in a 5 or 6 amp circuit breaker or stick to no circuit breaker at all like you suggested. Thanks in advance.
As far as the circuit breaker between the PV and the SCC from what you said Rmaddy I don't need one if I'm running the PV in series...I am definitely running the PV in series. Since the PV will only be putting out around 6 amps......should I put in a 5 or 6 amp circuit breaker or stick to no circuit breaker at all like you suggested. Thanks in advance.
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You misunderstood. You should have a 25amp breaker between the solar panel wires and the SCC. This helps protect the wires (10 ga / 30a) and gives you a way to disconnect the solar panels. You never want the panels connected to SCC if the SCC is not connected to batteries. It can build up heat and ruin your SCC.
You should have another breaker between the SCC and battery. In my case I have a Victron 100/30 and run 6 ga wire. So I went with a 40a breaker (Your 50a breaker would be fine). That allows the Victron to put out full power without tripping breaker and gives me a disconnect. It really isn’t for overload protection, the fuse near the battery is for that. It mainly for a disconnect.
So I can turn off panels to SCC, and I can turn off SCC from battery. Also that is the order in which to disconnect everything. The connect, reverse…. Turn on SCC to battery breaker, then Panel to SCC last.
Always fuse near the battery. Fuse based on wire size and length.
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Thanks STW. I'm getting most of what you said. I think the circuit breakers are to protect the WIRE and not to much the device at the end of the wire. So if I'm running 6awg from the SCC to the battery..... the "DC ampacity chart" says 6awg wire can handle 55 amps. So 50 amp circuit breaker should protect the before the wire melts at say ....56 amps. Hope that make sense. Is my thinking correct?
Actually the fuse at the battery is there to protect the wire. The circuit breaker is there as a disconnect, so it needs to be larger than the possible charge capability of the SCC so it doesn’t trip during normal charging.
The circuit breaker for the panels is also a disconnect. However if sized less than the 10 ga wire rating, which is 30 amp, it also protects the wire.
So you are wondering WHY do I need both a CB and fuse on the SCC to battery wire. Simply it’s because you need the fuse close to the battery. If you don’t fuse close to the battery and the wire gets a short you will have a melt down. You don’t HAVE to use a CB close to the SCC, but then how would you cut power to the SCC if you needed to? Disconnecting the wire is a pain, so a CB makes it easier. Also in my RV I may have it on storage (in garage) so no solar. Having the SCC on draws power and will run down battery. Being able to turn off SCC with CB solves that.
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