MC-4 connectors

Discussion in 'Off Grid Living' started by rsbhunter, Feb 15, 2012.

  1. rsbhunter

    rsbhunter Monkey+

    Ok, so with the panels being wired with the MC-4 connectors, how does somebody wire 2 panels in parallel? And then what do you do to connect the 5 strings (of 2 parallel panels) to a junction box? I have seen the connectors for sale, but no connectors that would allow you to tie two panels together, and then branch off to a jct box?,,,,I have heard that cutting the ends off is not a good idea, as IF a elec. insp. is needed, it won't fly....Any help would be great....rsbhunter ...ok, after looking at a solar site, i see that you can buy "multiple connectors" that i can hook two positive cables into, and one out....that way, i can just go in a "string" of 2 panels, 5 strings into a buss bar on the jct box...yes?
  2. TnAndy

    TnAndy Senior Member Founding Member


    You are connecting two panels IN SERIES ( not parallel ) You connect the MC4 positive ( and make damn sure you know which one that is and don't loose track of them when you get into the extensions that have no ends.....put some colored tape on those ends to mark them ) of one panel to the MC4 connector of the second will be a male, the other a female, so this happens to be exactly how they are designed to work......and you're left with a negative of the first, and a positive of the second. That is one string, of 2.

    From there, you will most likely need extension cables to run to your combiner box ( you did buy one, right ? ) unless the box is real real close to the panel mounting.....and since you have no idea where you're gonna mount them, you also have no idea how long to get the extension, huh ? The come in various lengths, like 15', 30', 50', 100', with a male/female connector on the ends. IF you need a 12' from the panels to the combiner box, then you buy 30' cables, cut them in half, connect the MC connectors to the left over ends of that pair above, then the cut ends go directly into the combiner box terminals/breakers.
    larryinalabama likes this.
  3. rsbhunter

    rsbhunter Monkey+

    MC-4 connectors...

    No, didn't buy a combiner box yet, as didn't know what brand i want to go with, but they only run from about $75.00- $ that's no problem... as for cables, i might just buy 100 foot of cable and some ends, make my own...or wait til needed and buy them.....although, watched the stock market report today, oil is headed up, by about a buck a barrel a day...for the last 2 days...hope it stops.....or everything will get more expensive fast....By wiring the panels in series, can the 2 panel strings , be wired in parallel to the combiner box, or do each string need to be wired individually to the combiner box? If they are wired seperatly (5 strings of 2 panels) does that help with a partial shade bringing down the whole array? ...Thanks, rsbhunter
  4. TnAndy

    TnAndy Senior Member Founding Member

    Wait until you price the crimping tool before you say that......several hundred bucks.

    Both of those are different ways of saying the exact same thing. You take the pos/neg lead from the pair and run it to the combiner box. The neg goes on the NEG common buss, the pos goes on a breaker, feeding a common POS buss.

    Then you repeat with the next string of 2....

    THAT is running in parallel.

    AT the POS buss of the combiner box, you have a breaker, and the incoming amps from the panel is, say for example, 8amps and 70v. When you wire the next string in, the volts on the output Buss stay the same, but the amps double.

    ANd when you get done, the volts are 70, and the amps are 5 x (amp of each string).

    The wire from the buss bars needs to be large enough to handle that amperage, and not allow more than 2-3% voltage drop to boot....generally you'd be looking at #4 or #2, but it could be larger, depending on distance from the combiner box to the charge controller(s)
    rsbhunter likes this.
  5. rsbhunter

    rsbhunter Monkey+

    cable distances

    TNAndy...i know what you are trying to drill in my there a combiner box that is a good choice in your, (or anybodies) opinion? Thanks for all the help
  6. TnAndy

    TnAndy Senior Member Founding Member need a Midnite 6 circuit box, and 5 breakers for it.
    (Sources below are for illustrative purposes only, shop wherever you want)

    Midnite Solar MNPV6 Solar Array Combiner

    5 breakers, get the 10amp version in your case:

    Midnite Solar MNEPV 150 VDC Solar Array Breakers

    You need 5 of these, they go in the knockout holes in the bottom of the combiner box, and you run the ends of the MC4 extension cables in thru them:

    Two Wire Cable Grip

    You'll also need some locally obtainable conduit to take the larger wire from the combiner box to the DC input point on the Outback power panel.

    Grounding/lightning protection:

    One per panel:

    GBL4 DBT Solar panel grounding lug UL

    One of these, screw it in the the side knock out of the Midnite Combiner box, connect as per instructions included:

    Delta DC Photovoltaic Surge Arrestor

    You'll also need: (obtain locally)

    #6 bare copper wire, panel to panel in the above ground lugs, and then enough to go to the combiner box, then to a 8' driven ground rod, and a clamp for the rod.

    You'll also need enough #6 bare from the power panel to that same ground rod.

    Mount racking:

    Thought of that yet ? You have the panels, now you need some way to attach them to whatever you're gonna attach them TO.
    BTPost likes this.
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