Some fusing questions

stereoman405
stereoman405 Solar Expert Posts: 56 ✭✭✭✭
in Solar Beginners Corner #1
I plan on running 4 REC 210's in (2) 60v series paralleled together. I'm trying to figure out where I need proper fusing / breakers. There will be about 75' of cable between the PV's and controller.

I was planning on using 2 of the MC4 multibranch connectors at the panels to get everything down to one pair of 6awg before the 75' run.

- Do I need to place my first set of breakers at the panels, or can I just have it mounted at the 'end' of the 75' near my controller?

- How do I transition from an MC4 to my 6awg? Do I just get a pigtail like THIS and clip an end off and butt connect inside a j-box near the panels? (Not buying the crimper for this small of a project.)

- Do I need to run a chassis ground from the panels to tie into the ground om my controller, inverters, etc? If so how do I do that? Just run a naked copper strand for the 75' from panels to controller? (I'm assuming yes, but I didn't know if the size of my array changed anything, or if there is a better way to do it.)

Thanks!
· Share on Twitter

Comments

  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #2
    Re: Some fusing questions

    Ok, there should be a breaker/fuse for each series string at the solar panels. You take a made up cable like http://store.solar-electric.com/10fomc4excam.html cut it to length an run it to a combiner box like this http://store.solar-electric.com/mnpv3.html. The cut end goes into the breaker (positive end only). negative end ti the neg bus bar. Then two wires 75' to another breaker in the DC distribution box.

    I would strongly recommend a lightning arrestor at Both the combiner box and dc distribution box. http://store.solar-electric.com/deliar.html

    Grounding: A ground wire should run from the panels http://store.solar-electric.com/gbdbtsopagrl.html to a ground rod. The case of the combiner box should also be grounded to this ground rod. Note: Do NOT connect the ground to the negative bus bar in the combiner box. The charge controller and inverter should have ther own ground wire and ground rod.
    · Share on Twitter
  • stereoman405
    stereoman405 Solar Expert Posts: 56 ✭✭✭✭
    #3
    Re: Some fusing questions

    Thanks! Just a few questions for you.
    audredger wrote: »
    Ok, there should be a breaker/fuse for each series string at the solar panels. You take a made up cable like http://store.solar-electric.com/10fomc4excam.html cut it to length an run it to a combiner box like this http://store.solar-electric.com/mnpv3.html. The cut end goes into the breaker (positive end only). negative end ti the neg bus bar. Then two wires 75' to another breaker in the DC distribution box.

    - So does the breaker at the end of the 75' in the DC distro box actually provide any protection since the ones at the combiner should have tripped first during a short? It seems like it would just be more for convenience so you have a local 'shutoff' for maintenance at the charge controller?

    - How would I create the parallel between my two series at the combiner box? Would I have the positive from each series go into separate breakers then have a combined breaker bus bar LIKE THIS with my 75' home run connected to it? (That's what I could gather from THIS PIC.

    - For the DC distro box at the charge controller, can I use just one larger box for all my remaining DC needs? (Charge controller IN/OUT, inverter runs from batts, DC charger feed to batts, etc...) Assuming I have the proper sized breakers of course.
    audredger wrote: »
    I would strongly recommend a lightning arrestor at Both the combiner box and dc distribution box. http://store.solar-electric.com/deliar.html

    - Do you have any wiring diagrams that show how these guys are wired? I've seen a few pics and think I have it figured out but I's like to verify my assumptions. From THIS PIC it looks like they tie into all three legs passively, but current doesn't actually pass through it at all until a strike, which I would then assume channels it all to the earth ground and trips all your breakers?
    · Share on Twitter
  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #4
    Re: Some fusing questions
    - So does the breaker at the end of the 75' in the DC distro box actually provide any protection since the ones at the combiner should have tripped first during a short? It seems like it would just be more for convenience so you have a local 'shutoff' for maintenance at the charge controller?

    Yes, it protects the 75' wire from possible short / malfunction of the charge controler and, it acts as a "switch" to turn off the power from the PV.
    - How would I create the parallel between my two series at the combiner box? Would I have the positive from each series go into separate breakers then have a combined breaker bus bar LIKE THIS with my 75' home run connected to it? (That's what I could gather from THIS PIC.

    No, most combiners come with a "comb" like http://store.solar-electric.com/comb-bus.html it installs into the tops of your breakers.
    - For the DC distro box at the charge controller, can I use just one larger box for all my remaining DC needs? (Charge controller IN/OUT, inverter runs from batts, DC charger feed to batts, etc...) Assuming I have the proper sized breakers of course.

    Yes, see http://store.solar-electric.com/mndc250.html or http://store.solar-electric.com/oufl501.html
    - Do you have any wiring diagrams that show how these guys are wired? I've seen a few pics and think I have it figured out but I's like to verify my assumptions. From THIS PIC it looks like they tie into all three legs passively, but current doesn't actually pass through it at all until a strike, which I would then assume channels it all to the earth ground and trips all your breakers?

    I have no idea of what that pic is showing! I don't have a wiring diagram to share perhaps someone else does.

    How this helps
    · Share on Twitter

Categories