What is the main reason of upgrading panel from 100A to 200A???

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  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???

    So u tell me on 125 Amp Main I can connect 40A solar breaker ??
    Loads are 80A
  • BB.BB. Super Moderators, Administrators Posts: 29,321 admin
    Re: What is the main reason of upgrading panel from 100A to 200A???

    As I understand, unless you change to a 100 amp main breaker, the answer is no.

    If you change to a 100 amp main breaker, and the rest of the load breakers add up to less than 125% of the 100 amp breaker (if residential)--then you can.

    -Bill "not a code expert" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • newenergynewenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???
    Batikikik wrote: »
    So u tell me on 125 Amp Main I can connect 40A solar breaker ??
    Loads are 80A

    If your main is 125 amp and your busbar is 125 amp, the most you can connect is 25 amps of solar.

    If your busbar is 125 amp, you could downgrade the main to 100 amp and then connect your 40. This is easier than other changes we've talked about since a 100amp main should be pretty easy to find and not cost *too* much.

    (depends on manufacturer/age of course)
  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???

    ok , thank you ... I think the same way :)
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???
    BB. wrote: »
    If you change to a 100 amp main breaker, and the rest of the load breakers add up to less than 125% of the 100 amp breaker (if residential)--then you can.
    Not quite - you have to run a load calculation to see if can run a 100A main breaker or not. You can have a lot more than 100A of loads plugged into a 100A main.
  • solar_davesolar_dave Solar Expert Posts: 2,343 ✭✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???
    drees wrote: »
    Not quite - you have to run a load calculation to see if can run a 100A main breaker or not. You can have a lot more than 100A of loads plugged into a 100A main.

    Something tells me that the local code guys are not going to buy off on a 40A add to a 100 amp panel, especially if there are slots left in the panel after the load calculations.
  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???

    No I dony need to do claculation beacuse I am gonna install SB4000USwith 25A breaker ,,,,and main will be 125 A
  • solar_davesolar_dave Solar Expert Posts: 2,343 ✭✭✭✭
    Re: What is the main reason of upgrading panel from 100A to 200A???
    Batikikik wrote: »
    No I dony need to do claculation beacuse I am gonna install SB4000USwith 25A breaker ,,,,and main will be 125 A

    If you have a permit for this design then more power to ya!. ;)
  • Energy EfficienciesEnergy Efficiencies Registered Users Posts: 11
    Re: What is the main reason of upgrading panel from 100A to 200A???

    Please bare with me, as I read the original post and a few responses...and I am drinking beer, but it seems there are a lot of different views on this. Mostly it seems people dont understand the reasoning behind the 120% rule. Basically the bus bar rating is what the bus bar can handle from a "utility source". One utility source is the grid electricity from your electric provider coming to your panel. Another is your PV system. Both are considered Power production systems, or utility sources. It doesnt matter how many breakers are in the panel feeding your lights, dryer, etc..You may pop a breaker....but the bus bar is rated for power coming in, not the various circuits in your panel using that electricity. So whoever posted something along the lines of stay away from my house....go look in your panel. You BETTER RUN! lol.

    Now I will try to explain the rating....lets say you have a 100A main breaker in your panel. This doesnt necessarily mean it is a 100A max panel. You need to look at the MAX panel rating. A lot of times there are 100A mains in a 200A panel. And sometimes panels arent maxed at 200A. If it says "XXX"amp bus bar rating, that is all you can rate for. Then multiply that by 120%. You then subtract the main breaker from that number. What is left is what you are allowed max to use for a breaker on your PV system...

    What I dont understand through the posts I have been reading is why everyone acts like it is taboo to do a line side tap. I do them all the time in CO. YOu have to install an AC disconnect anyway. So if you get a fused disconnect and then line side tap, all of this post is moot. Also I have heard rumor that the NEC 2011 will require line side taps for RE systems...so learn what you are doing, and save the money doing a system upgrade that you dont need.

    And as I have always understood, your home load calculations dont matter a bit...at least here in CO. They are SUCKING electricity...not heating the buss bar..
    Good luck!
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