Cable too large for a main / sub panel lugs

fasterski
fasterski Registered Users Posts: 14 ✭✭
edited September 2017 in Construction #1
I have a question somewhat related to solar. Well not really .  I'm hoping to get some info here.

I'm building house and a garage in the cottage country. Due to the lot location the best way to get connected to hydro was to go to the garage first. Distance from the garage to house is over 200 ft. I had the trenching work done by local contractor. I had hydro connected to the garage with 200 AMP service. ESA inspection has passed for service only (1 plug connection in the garage). I'm doing all the work with permits pulled in homeowner name.

 I have 4/0 AWG wire (aluminum)  that I need to connect to the 100 AMP pannel at the house. The 100 AMP main lugs won't fit that big of a wire. Secondly at the 200 AMP panel in the garage I have to connect the 4/0 wire to either main rails of the service or somehow connect to 100 AMP breaker.

What are my options to make the connection safe.  I have gone to electric supplies shops all over and no one is willing to help. Electrical contractors won't help as they say they need to have the permit in their name.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited September 2017 #2
    Assuming, by reference to cottage country, as well as hydro, your location is in Ontario Canada, if so, using a larger interconnect cable between the garage and the house to prevent voltage drop is possible. In order to accommodate the lugs of both the 100A circuit breaker in the 200Ah panel and the 100A house panel lugs, a junction box at either end, transposing to a smaller gauge capable of handling 100A would be acceptable. The junction boxes are required because splices are not acceptable within a distribution panel,, but as long as the overcurrent protection is rated for the lowest gauge  conductors used, there shouldn't be a problem. Pass this by the inspector and get his/her blessing, don't just take my word. 
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  • fasterski
    fasterski Registered Users Posts: 14 ✭✭
    #3
    mcgivor said:
    Assuming, by reference to cottage country, as well as hydro, your location is in Ontario Canada, if so, using a larger interconnect cable between the garage and the house to prevent voltage drop is possible. In order to accommodate the lugs of both the 100A circuit breaker in the 200Ah panel and the 100A house panel lugs, a junction box at either end, transposing to a smaller gauge capable of handling 100A would be acceptable. The junction boxes are required because splices are not acceptable within a distribution panel,, but as long as the overcurrent protection is rated for the lowest gauge  conductors used, there shouldn't be a problem. Pass this by the inspector and get his/her blessing, don't just take my word. 
    Yes , I'm in Ontario.  Thing is the inspector saw the 4/0 cables in the main panel (it would have been a real pain to pull them in after the panel was mounted) and his exact words were "I guess you will have to" when  I indicated I will pig  tail them into the 100 AMP breaker) Hence  the thread. I  have a rough in inspection next month would love to get the house connected before the winter.
    So the idea of the junction boxes is great but I want to exhaust all the other avenues.  Thank McGivor.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Either split bolts, or splice blocks, in a J-Box outside the Panel.  Must be rated for CU-AL application
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  • softdown
    softdown Solar Expert Posts: 3,915 ✭✭✭✭
    #5
    If it was a simple cabin in the woods, one might remove enough wires to fit into a lug that would fit. 1/2" of slightly reduced cabling should not have a disastrous impact since you are using 4/0. 4/0 AL is about the same as 2/0 CU.

    Having said that, I really hate to remove wire strands. I just buy bigger lugs and grind on the sides until the lug fits....if I have to. 


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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #6
    mcgivor said:
    Assuming, by reference to cottage country, as well as hydro, your location is in Ontario Canada, if so, using a larger interconnect cable between the garage and the house to prevent voltage drop is possible. In order to accommodate the lugs of both the 100A circuit breaker in the 200Ah panel and the 100A house panel lugs, a junction box at either end, transposing to a smaller gauge capable of handling 100A would be acceptable. The junction boxes are required because splices are not acceptable within a distribution panel,, but as long as the overcurrent protection is rated for the lowest gauge  conductors used, there shouldn't be a problem. Pass this by the inspector and get his/her blessing, don't just take my word. 
    I am fairly certain in the USA splicing a large conductor to a smaller is allowed within the breaker panel s long as all 3 conductor ends stay within the panel.  The breaker will need to be rated for the smaller conductor. Meaning you cannot splice conductors inwithin the panel and rout back out again like you would in a junction box.

    Sounds like the inspector already knew the solution.

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