Breakers for dmppt

[Josh Peterson]

Does anyone have suggestions for the 100 amp breakers for the input out put of the DMPPT? I will be mounting them on a din rail.

[Dacian Todea]

Josh,

I think 63A is the limit for normal thickens breaker There are 100A even 125A but they are 2x as thick so you can fit two of those 63A one in the same space and maybe more convenient depending on how you have the heating elements split up.

Make sure they are DC rated breakers as open circuit voltage can be around 40V

Also breakers need to match your cables not the DMPPT450 rating so say you use 10AWG wire to the heating element then that wires should be protected by a 32 or 40A breaker normally depending on the type of cable insulation and local rules.

[Plamen Yordanov]

     Hi Dacian,

  I think I've seen on some pics of your setup that You're using 63 amps breakers for the 6mm2 cables. And what will be the minimum for one 260 - 280 watts PV panel. Like 16amps is enough or should be more?

[Dacian Todea]

Yes minimum for a single 260 to 300W panel should be 15 to 16A as they will output 10A in cold sunny days (especially February, March is when I see that in my setup) and you can have 12A for a few minutes even with edge of cloud effect.

I have 63A breakers for groups of 4 panels each group of two has 6mm2 cable this then go to my DMPPT450 and from that to SBMS120 that has ideal diodes on the inputs so current from battery can not flow back.

If there where to be a short circuit on any of the PV wires (super unlikely) then max current will be the one coming from the other group of two panels so max 20A and breaker will do nothing as this is not trough the breaker but I have those mostly as a way to easily disconnect the PV array. Initially I had MC4 fuses on each individual panel but those where low quality and many failed (not the fuse but the MC4 fuse holder so I removed all of them).

You can have 32A breakers for just one group of two parallel panels connected on one of those 6mm2 PV cable.

[Plamen Yordanov]

Thanks Dacian!