When is a bigger breaker panel needed?


Old 01-06-06, 01:05 AM
Thread Starter
Join Date: Jan 2006
Posts: 5
When is a bigger breaker panel needed?


I'm refinishing the basement, and will need to be adding several new circuits (4-5 15A and 3 20A 110V) Can someone tell me how I calculate if the existing 200amp service will support these additions? (or, how much extra do I have left...)

Also, I'm considering putting in a sub-panel for my workshop for easier access and future modifications (Sub-panel would be only about 15-20' from the main panel, but a longer walk once the walls are up.) The shop will be using 2x15A/110, 2x20A/110, and an existing 40A/220 circuit. I might like to add a couple more 110 or 220 circuits in the next year or two. Anyone have a rough guess what just having the sub-panel wired up would cost from a pro? Or do you think I oughtta just bite the bullet and work it out meself? (I'm quite comfortable with wiring the switches, outlets, etc., but haven't done any panel work.)


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Old 01-06-06, 05:41 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Google the term "demand calculation" or "demand load calculation" to find quite detailed information on how to determine if your panel can support the load.

As for the physical circuits themselves, you can see if your panel box is full or if there are open slots.

As for new circuits, I recommend that you do not install any 15 amp 120 volt circuits. Rather, make them all 20 amp circuits. They only cost a few dollars more and provide one third more power.
Old 01-06-06, 11:08 AM
Thread Starter
Join Date: Jan 2006
Posts: 5
Thanks Bob,

Just a rough WAG at the numbers and it looks like my 200A service should be fine, but I'll check up on the detail when I have some time (and before I do any wiring...)

I'm still working out exactly how many new circuits I need to add, but it looks like there's room in the main panel for all of 'em. If it turns out to be cost-effective, I'd still like to run a sub-panel in the new shop before I drywall things in - it'd be a whole lot easier to add circuits in the shop that way, and quicker to get to when I trip one. Any ballpark estimates on what installing a 60 or so amp panel would cost me DIY or with a pro? Just trying to decide if that's a reasonable path to go down.

Old 01-06-06, 07:40 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
A 60-amp subpanel is pretty cheap. A nice SquareD Homeline panel with five 20-amp breakers thrown in, with a separate grounding bar and neutral bar already installed, can sometimes be had for less than $40. Your only other cost would be the 6/3 cable to feed it, and the cost of that depends on the distance.

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