Proper wire gauge recommendation for installation of 125 amp sub panel. The sub panel will be located one floor below the 200 amp main panel and need about 14 feet of wire for a neat installation. Should I use #3 or # 2 copper? The local store clerks are steering me toward aluminum wire, I believe using alum. requires upsizing the wire gauge making it harder to work with. A check of wire capacity tables tells me for this short of a run even #4 copper would carry the load with little voltage drop. Thanks in advance, Bill
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
The RealTruck AMP Research Bedsteps give you easy access to your truck-bed storage.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
Just curious, why the big subpanel? Just because they call it a 125A subpanel doesn't mean that you have to supply that much current to it. Can you even get 125A breakers for the main panel that will supply the sub? I think I've only seen 100's. If it is for a shop or something, I'd suspect that 60-80A would be adequate power for any tools that were being run. Most people I know will use a 12-16 space 125A panel in their garage or workshop, but will supply it with 50-60A over #6 from their main panel.
I had been running all basement circuits including those from workshop to main panel. The panel was getting rather full and the extra conduit I routed to basement had gotten full of romex. Now I'd like to run 220V circuits for dust collector and future tool purchases. We are also in beginning stage of a basement remodel and I'd like the ability to add several more circuits all neatly run to the basement's own panel. You are correct that a smaller panel might suffice. My upstairs panel reveals my tendency to overdue the amount of circuits. The panel I purchased has a 125 A main breaker and I have also purchased a 125 A breaker for the supply from main panel. My plan is to maintain the basement light circuit to main floor panel and all others would get rerouted to the basement subpanel.
I can just hear the electricity police now, "Sir step away from the Alum."
Use the Cu, don't use the Al. Damn stuff will work harden on you fast and be tough to pull. Not to mention all the other issues with it.
"The panel was getting rather full and the extra conduit I routed to basement had gotten full of romex."
Having all of those runs together require that the cables be derated because of the extra heat build up. For example if you have 10 current carrying conductors you have to derate the capacity of the wires by 50%. And 5 120 only circuits is 10 current carrying conductors.
Use the #2 CU, nothing lighter.
Don't forget that it's a subpanel and you need to run for wires, the 2 hots, a neutral and a separate ground and you have to keep the neutral and grounds separate in the subpanel.