wiring my pv's

Maybe you guys can help me out. I bought three 24volt 160 watt BP Solar panels to add to my system. These panels have a closed junction box with mc connectors for wiring. The diagram clearly shows the short mc connector on one side of the box to be plus and the long mc connector from the other side of the box to be minus. However, when I hook my volt meter to them, the meter reads the opposite. Now, I've called my distributor for the panels and they told me to trust the meter, not the diagram. I'm inclined to do just that. But still, I'm concerned that the manufacturer would take the time to draw a diagram that shows the wires to be configured one way, but in actuallity, they are opposite. I tried to call the manufacturer, to talk to some techy who could give me a diffinitive explanation of the diagram, but I got no where with my phone calls. Everyone referred me back to the distributor. The only reason I checked the polarity to begin with is because I'm cutting the mc connectors to splice in a #6 wire to the panel. I can't open the junction box to check polarity there. What do you think, should I trust the meter and wire them up? My electrician told me I could splice a 10 amp breaker on the plus side for "just a case", but I'm still reluctant to make the connection, even on just one of the panels. The panel will be wired to a combiner box with an 8 amp outback breaker on that panel. Maybe I'm being over cautious, but I don't want to burn up my panels because of some boneheaded mistake. Please help ease my mind with this confusion I'm feeling. Thanks folks.


  • BB.
    BB. Super Moderators, Administrators Posts: 33,522 admin
    Re: wiring my pv's

    Trust (the meter), but verify...

    Double check the meter on your car's battery just to be sure that everything is right.

    Next, I believe that some manufacturer's will void the warranty if you cut off the MC connectors on their solar panels.

    And, if you wish, just buy some pre-made MC assemblies and cut those to meet your needs:


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dhill
    dhill Solar Expert Posts: 47
    Re: wiring my pv's

    Thanks Bill. I have double checked my meter and re-checked my readings. I guess I'm just finding it difficult to believe that the manufacturer would show a diagram that is so clearly wrong.
  • Roderick
    Roderick Solar Expert Posts: 253 ✭✭
    Re: wiring my pv's

    My Mitsubishi panels have MC connectors, and the spec sheets admit that the lead length could vary widely. Rather than look at the lead length, can you tell us whether the male connector (the one with the prong sticking up in the middle or the female (the one with just a hole) is the positive?

    Although it's unlikely that your meter is backwards, if you want assurance, you could check the polarity by measuring a plain old flashlight battery.