Circuit Sense Check

You learn in life that assuming you are right can be dangerous. That being said, I would welcome any corrections or suggestion to my attached wiring diagram. I think I need to add
a cut-off between the PV panels and the combiner box. The Midnight Solar 200 charge controller has its own arc fault circuit. The combiner box breaker feeding the well pump is for emergency use only if normal grid power was down and my off-grid inverter was also down.) A Grundfos SQF well pump will run on both AC and DC voltages. I would also switch off the charge controller breaker if I activated the DC pump circuit which could only function in daylight. Thanks for your input. Attachment not found.

Not sure my attachment is here. If not let me know.


  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Circuit Sence Check

    Welcome to the forum TexasDan.
    First thing I notice, perhaps I misunderstand your drawing, but it appears you have your 4 PV panels all wired to short circuit each other. (+ from PV1 going to - of PV2, and + from PV2 going to - of PV1) Repeat for PV 3 and 4.
    If they are 24 volt panels, then all + should be connected together and likewise all - should be together.
    Also, there is no need to triple fuse in the combiner box as presently shown. I would however bring in a positive lead from EACH PV and fuse EACH PV input to the combiner box. And personally, I'd have either a breaker or disconnect between the combiner box and the charge controller, so power could be disconnected from the CC. Furthermore, if each of your 4 PV panels output 8 amps max, then they'll be trying to push over 30 amps through that existing 15 amp fuse, and it ain't gonna like that one bit.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: Circuit Sense Check

    It looks like he is trying to run one series string with all 4 panels. He list a vmp series value of 117v that would have an imp of 8amp. I would be a little concerned of the voc on cold days. The classic could go into hyper voc and disconnect from the panels. Dan if you are doing a series string with all your panels, make sure you go + to - from one panel to the next all the way across. Looks good otherwise.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Circuit Sense Check

    Voc would hit 194 at worst which the Classic 200 can handle.

    (Calculated from what Ned wrote - I can't see the diagram well enough to render any help.)
  • boBboB Solar Expert Posts: 1,004 ✭✭✭✭
    Re: Circuit Sense Check

    From the wiring drawing, it looks to me like you have 2 modules wired in series and the other 2 modules wired together but
    not being connected to anything besides ground on the frame.... I am assuming that's the frame hooked to the ground ?

    Also, it is not normal, and possibly harmful to the Classic to wire the pump across the PV and Classic input terminals at the same time.

    Some have wired their pumps across the PV wires along with the controller, but a diode should be used to isolate the pump
    from being powered by the battery, through the Classic, back feeding out its input terminals.

    Aside from these points, the wiring looks OK I think.

  • TexasDanTexasDan Registered Users Posts: 10
    Re: Circuit Sense Check

    Yes my panels are shown in series and add up to 117volts. As the classic 200 can handle up to PV 200 volts, cold weather should not be a problem, which is why I did not purchase the a classic 150. Several knowledgeable responders both here and from a premier solar company found fault with the possibility that the CC and well pump could both be switch on at the same time. The best suggestion I received was to replace the two 15 amp breakers with a 3 pole switch (i.e. CC/OFF/PUMP) so only one circuit could be active at a time and and an off (both off) position would available for exactly that. Breakers for the CC or pump would then be added down line. Anyone know a good source for a 3 pole DC din mounted rotary switch or perhaps some sort of 3 pole breaker... I saw one once. Thank ya'all for your input!
  • Robin GudgelRobin Gudgel Registered Users, Solar Expert Posts: 58 ✭✭✭✭
    Re: Circuit Sense Check

    Check out our wind turbine stop switch. It can be connected as a transfer switch. The 150V breakers are good for 165 volts. We can also make it using 300V breakers, but I don't think you need them.
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