How close to breaker panel?

EllieThomas
EllieThomas Registered Users Posts: 12 ✭
in Solar Beginners Corner #1
I've talked to a local Solar store and they said that it didn't matter how far the solar panels are from the AC breaker panel.

Does this matter? I would think that the wire size and cost would be high since it will be a long way but I am completely new at this.

Thanks,
Ellie
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Comments

  • James
    James Solar Expert Posts: 250 ✭✭
    #2
    Re: How close to breaker panel?

    The advice you received is somewhat correct...your DC wiring length from PV array to controller & batteries is more critical due to line loss at low, dc voltages. AC wiring from inverter to load panel is not as important, but still adds up when you look at the cost of copper these days...
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: How close to breaker panel?

    actually the info is incorrect that effie received from that solar store and that effie's own intuition or knowledge or whatever may apply here is correct that as james stated the losses increase with distance and so do the wire costs as a result. test them and see what they say for a distance of 1000ft. if they still say it doesn't matter then don't deal with them at all.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #4
    Re: How close to breaker panel?

    There are several different wiring runs we are typing about here...
    1. Solar panels to combiner box / breaker (short run)
    2. Combiner Box to Charge controller (may be a long run)
    3. Charge controller to battery bank (short relatively heavy wire)
    4. Battery bank to inverter (short very heavy wire)
    5. Inverter to 120 VAC loads (short/long, normal house wiring/extension cords)
    Note that #1 and #2 may do the Combining with or without a combiner box/breakers--depends on size of solar array and how it is wired.

    The wiring runs where you generally "allow/support" long wire runs are #2 and #5.

    Runs #3 and #4 need to be kept short and heavy wiring to reduce voltage drop and carry heavy currents to/from the battery bank.

    That is a general answer--the specific answers will depend on the design for your system (how many solar panels, how long of wiring runs, what voltage battery bank, what type PWM or MPPT charge controller, and how big of inverter / loads you are using).

    It is a bit confusing to talk about things generically--but if you want to ask specific questions related to your system--please go ahead. It is less confusing when we talk specifics and go through the calculations instead of just waving hands.

    Also, you did not say, but the above is based on designing an Off-Grid system.

    For a Grid Tied System (solar panels + GT inverter only--no battery bank), it is less complex--but still important to do it right. Generally the long cable run is between the solar panels and the GT inverter. And a short run from the GT inverter to the house breaker panel...

    If the wire run is too long between the GT inverter and the House/Transformer on the pole--you can have problems with the GT inverter turning off because of Voltage Rise between the Inverter and the Pole Transformer.

    If you want more details, please ask--I don't want to go too deep into the explanations if it does not help you (wrong system type or not answering your question).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • EllieThomas
    EllieThomas Registered Users Posts: 12 ✭
    #5
    Re: How close to breaker panel?

    Thanks very much. It is correct that I didn't give specific information. I am only in the gathering of information stage so I really don't have much to give. It will be an off grid system and a 4000 or 4400 watt inverter most likely.

    I do know that the solar panels and batteries would be in one place and the connection to my breaker box would be far from them given the layout. I won't even be able to do this if that is very important that they be close. I don't know how far... I can measure and will do that soon, but it is the length of a good sized house, and drive way.

    Ellie
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #6
    Re: How close to breaker panel?

    For the most part, you can go a fair distance with the solar array to charge controller (can get around 80 to 100 VDC maximum).

    Your 120 VAC / 240 VAC (if 240 VAC is needed) is the higher voltage and easier to send longer distances (lower current, higher allowable voltage drops).

    Remember that Power = Voltage * Current...

    If voltage is 2x higher, then current is 1/2. So you can use 1/2 the thickness of copper wire to go the same distance (and 1/2 the cost).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jcgee88
    jcgee88 Solar Expert Posts: 154 ✭✭
    #7
    Re: How close to breaker panel?
    EllieThomas wrote: »
    I've talked to a local Solar store and they said that it didn't matter how far the solar panels are from the AC breaker panel.

    Does this matter? I would think that the wire size and cost would be high since it will be a long way but I am completely new at this.

    Thanks,
    Ellie

    There are first installation effects, which are one time,
    and then operational effects, which apply for the rest of
    the life of the array. I'll share with you some of my
    recent real life experience on this topic.

    For installation, long runs obviously take longer to
    install, and the materials cost most. Your contractor's
    bid may reflect that. More subtle, there may be
    additional time needed (whose costs you won't pay),
    which will delay getting in production. This includes runs
    out to the hardware store to get additional material
    (happened to me!) and utility inspection time. On
    the latter, for me, the utility inpector did not approve
    the initial line run, and this had to be redone (the original
    line was run about twice as long to take advantage of
    an existing chase from attic to circuit breaker box).

    If you are considering using micro-inverters, be
    aware they come with a max distance specification.
    That's to enable data communications between the
    micro-inverters and their control unit (which is typically
    installed near the circuit breaker box and near a network
    drop)...data flows over the power lines between the
    micro-inverters and their control unit. In my case, if we
    had been by chance "too far," we would have had to
    move the control unit to the attic, where it would have
    been exposed to much harsher environmental conditions,
    and I would have had to run a network drop up to
    the attic as well.

    Operationally speaking, my contractor attributes 1-2%
    power generation loss due to line losses. So, the longer
    the lines, the larger fraction of loss you will incur.
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