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Question DetailsAsked on 5/28/2015

what is a 200 amp 30/40 electrical panel with main breaker?

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Means a 200 Amp capacity (so normalish size for normal size (about 2000SF) modern homes) with a main breaker (protects against overall overload of electrical service) at the top of the panel (as opposed to a separate main breaker say outside by meter), with 30 breaker slots and neutral/ground buses able to handle 40 circuits (actually 40 110V circuits - 220V counts as two, sort of).

The 30/40 needs a bit of explanation - the 30 breaker slots means space for 30 full-width breakers (electric range, water heater, furnace, dryer, and maybe dishwasher if heats own water or steam type each take 2 slots (double breakers), so that really leaves you typically about 20-26 outlet and light circuit slots, minus any double breaker (220V) circuits needed for pool / sauna / hot tub heating or large garage power tools like welders, air compressors, large table or radial saw or planer, etc, to feed lighting and outlet circuits.

The 40 circuit designation generally means the neutral and ground buses can handle a maximum 40 neutral and ground leads coming in - 1 to each 220V double breaker setup even there are two "hot" leads going to the two breakers, and one to each 110V circuit of course, but with 30 breaker slots you can only bring in 30 circuit leads, not 40, unless you use half-width breakers in about 10 of the slots. Depending on how many 220V circuits you have, that can actually mean well less than 40 circuits in most cases because each 220V item requires two breaker slots.

If a lot of those are circuits that are not loeaded to anywhere circuit capacity using half-width breakers or dual-circuit breakers (so two circuits fit in slot ofr one) that can work, but get carried away and you can easily overload the breaker box and cause overheating and tripping out of the main breaker. Personally, I hate the half-width breakers because I have seen too many overheat and cause fires, so I would spend the extra probably $100 or less to get a 40/40 box rather than a 30/40 if you need that many circuits.

Course, buy the time you add up the box load (which is NOT just the total of the breakers, but is figured using an equation that estimates the percentage of total circuit loads you are likely to use at one time), if you are loading your box up with 40 circuits you may well find that you need a 250 or 300 A box anyway - rare, but getting more common these days with the added loads from "smart" homes, large home entertainment systems, masses of decorative lighting, in-law apartments (with second kitchen etc), and added loads from hot tubs / pools / electric saunas and electric car plug-ins.

If talking an upgrade, you can find several prior quetions with answers on typical costs and issues right below this answer, plus more linked below each of them.

Answered 4 years ago by LCD

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