Now to put it together...

Hello. I plan on installing my own 7KW PV roof mounted system in the next few days and I could use some professional advice.

I have been a building contractor for 30 years and am experienced in AC electric, but know little about DC or solar installations.

I purchased the following components on the advice of a salesman:

24- JA P6 72-285/3BB PV panels (Multi Crystalline)
1- Xantrex XW6048 Grid-Tie inverter (6000 watts) (open circuit voltage 45)
2- Outback Flexmax 80 charge controllers 80 amps MPPT
16- 12V 170AH solar batteries
1- Xantex XW Distribution Panel
1- Midnite MNVP12 Combiner box
12- 20A 150 VDC single pole din breakers
4- 80A 125VDC single pole breakers
2- Delta LA302DC lightning arrestors
1- Delta LA302R 300VAC lightning arrestors
1- Xantrex Auto Generator Start
1- XW remote system control panel


Here are some of my questions:

How should I wire my panels with the MC4 wires to go into the combiner box? 24 panels and 12 breakers 20A?
Do I have to cut off the end of the MC4 to connect it to the breakers?
Why do I have 12- 50’ MC4 cables? Don’t the panel cables hook into each other?

What size wire should I use to go from the combiner box to the distribution panel (25’)?

How should I connect my batteries to go into the distribution panel? I have only 2- 10’ 4/0 inverter cables and 16- 1’ 2/0 battery cables 4- 80A 125VDC breakers

Will the Outback charge controllers be compatible and communicate with the Xantrex control panel? Why do I have 2 controllers?

Where do I install the 3 lightning arrestors?

Looks like I have to connect the big DC disconnect in the distribution panel to the 80A breakers?? What size wire? Why do I have 4?

Thanks

Pierre ><>

Comments

  • BB.BB. Posts: 27,699Super Moderators admin
    Re: Now to put it together...

    Pierre,

    That is a big project to start with!

    What size Battery Bank do you have?

    You are planning on Grid Tied operations (feeding power back to the utility)? Do you have pre-approval from your utility for GT connection/operation?

    -bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stephendvstephendv Posts: 1,571Solar Expert
    Re: Now to put it together...
    Pierre wrote: »
    How should I wire my panels with the MC4 wires to go into the combiner box? 24 panels and 12 breakers 20A?
    Do I have to cut off the end of the MC4 to connect it to the breakers?
    Why do I have 12- 50’ MC4 cables? Don’t the panel cables hook into each other?

    Hi, I'll answer what I can:

    With 24 panels (the 72 cell variety), you'd need to create 12 sets of 2 panels in series. I.e. you connect the + and - of two panels together, then you connect your long mc4 cables to the remaining + and - and those cables go to your combiner box. That forms 1 set. If you have 12 MC4 cables in total, then it seems whoever advised you to get them intended for them to be cut in half so that the ends without mc4 connectors go to your breakers in the combiner box.

    The outback controller won't talk to the Xantrex components, but it's not necessary that it does. Would have been nice to get everything Xantrex, but the system will work fine with the outback controller. You only have 1 controller listed, the Xantrex control panel is purely to program and monitor the Xantrex inverter.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Now to put it together...
    Pierre wrote: »

    Here are some of my questions:

    How should I wire my panels with the MC4 wires to go into the combiner box? 24 panels and 12 breakers 20A?
    String sizing tool for Outback will help you figure out the best configuration.
    Do I have to cut off the end of the MC4 to connect it to the breakers?
    No. Absolutely do not do this. MidNite combiner boxes come with MC4 connectors built in.
    Why do I have 12- 50’ MC4 cables? Don’t the panel cables hook into each other?
    Some of the panels will definitely hook to each other. You may need some cable length to go from each string to the combiner box. You probably do not need twelve of them. Salesmen like to sell stuff.
    What size wire should I use to go from the combiner box to the distribution panel (25’)?
    This will depend on how the array is configured, and the distance between combiner and distribution box.
    How should I connect my batteries to go into the distribution panel? I have only 2- 10’ 4/0 inverter cables and 16- 1’ 2/0 battery cables 4- 80A 125VDC breakers
    Did I mention salesmen like to sell things? Did I also mention they often don't have a clue? There's no way wire type/length could have been determined without planning the installation locations first. Unfortunately we can't tell you how to do it without knowing the distances.
    Will the Outback charge controllers be compatible and communicate with the Xantrex control panel? Why do I have 2 controllers?
    The Outbacks will not talk to the Xantrex. You should have got a Outback Radian inverter instead. Salesmen again. You have two controllers because the combined current for the total array exceeds what one can handle.
    Where do I install the 3 lightning arrestors?
    Good question. Combiner box will probably be the location for at least two of them; one on each half of the array (divided for the two controllers). The other may be intended for the AC output or input or .... who knows where. Salesmen again I'm afraid.
    Looks like I have to connect the big DC disconnect in the distribution panel to the 80A breakers?? What size wire? Why do I have 4?
    Salesmen again. If you have breakers you don't need a disconnect as well (unless local code requires it). Wire sizing is once again a matter of current, Voltage, and distance. This stuff isn't "one size fits all" and needs to be planned in advance, not just a bunch of equipment and parts sold to people.

    Frankly the project size here is so large that a first-timer should not be taking it on. You really need the help of a qualified installer on site to work out the details.
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: Now to put it together...
    Pierre wrote:
    Looks like I have to connect the big DC disconnect in the distribution panel to the 80A breakers?? What size wire? Why do I have 4?
    Welcome to the forum,

    You have 4 strings of batteries (each string is 4 batteries in series), and the 4 strings are in parallel. That is a poor design for batteries that are meant to be frequently cycled, but is not so bad if they are primarily meant to float (for backup use). The four 80 amp breakers are meant to go in each battery string... if one string develops a shorted cell the breaker will hopefully trip before a fire occurs.
    MidNite combiner boxes come with MC4 connectors built in.

    They come both ways. If yours does not have built-in MC4 connectors, then cut the MC4 extension cords in half and put the cut end into the combiner box. Do not ever cut off the MC4 connectors on the solar panels.

    I agree with the others that you should get some experienced help... or at least get your salesman to give you a wiring diagram.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
Sign In or Register to comment.