Electrical help, have 400amp service?

Question

I am wiring a house for a guy and he says he is going to have a 400amp service. I havn't done residental in a while and am struggling to remember how this goes. You have your meter with one serivice wire coming in, and that will hit one 200amp panel, and will have have a load side and you can jump out with another service to feed the second 200amp? And what it a good AWG for the service.

Also - they make 20amp arc fault breakers right? all I've ever used is 15amp but this guy is using 12AWG / 20 amp for general receps.

Answer 1

Any electrical service over 200 amps need to be metered through current transformers (CTs). Most utility companies will have a book they publish with their specifications.

Here in Montana, we are required to use a 36x36 CT cabinet for a 400 amp service. Typically, you install a fifth jaw meter base to one side of the CT cabinet, then the CT cabinet and finally the 2 disconnects on the opposite side of the CT cabinet that the meter base is on. A typical 400 amp service, with the meter base, CT cabinet and 2 disconnects, will take up a space approximately 7' wide.

For sizing your feeders you use NEC table 310.15(B)(6). To size your grounding electrode conductor use NEC table 250.66. To size your equipment grounding conductor use NEC table 250.122.

Yes they make 20 amp arc-fault breakers. Don't forget, you can't share the neutral on arc-fault circuits. This means no 3-wire "home runs" for your bedroom circuits.

This is a job for a licensed electrician. When you get into services over 200 amps, they get complicated. Even if the homeowner has the permit, you are still required to be licensed to help them.

If you need further assistance, please visit:
http://electricalblog.gilchrist-electric.com

Answer 2

You are correct as far as the Line supply Hitting a Meter/CT cabinet in the Middlehttp://www.sea.siemens.com/resident/images/metercombophotos/MM0404L1400RLM_Straight.jpg, on one side I would set a 200 Main Breaker Disconnect to feed your 200 amp Main Panel In the Househttp://www.sea.siemens.com/resident/images/metercombophotos/MM0404L1400RLM_Straight.jpg, on the other side I would set a 200amp Main Breaker with feed thru lugs (similar to a Mobile home Panel outside)http://www.sea.siemens.com/resident/images/metercombophotos/MM0404L1400RLM_Straight.jpg, This way you can still feed a sub-panel in the basement and Have spaces in that panel for you 220v equipment, such as a/c's, Range, water heaters etc... a 400 amp service is not uncommon at all, 200amp feeder 4/0 aluminum with a 2/0 aluminum for Neutrals, and Yes they do make 20 amp arc-fault breakers, I hope this helps

Answer 3

Why does this person need 400 amps? You are right about 15 amps and something like a maximum of 110 volts as a standard for most North American products that require electricity, except for the larger appliances like your fridge, stove, washing machines, and dryer (usually over 20 amps and require a 220 volt outlet). You are also required to have an electrical license to install wiring in a home to ensure that no-one gets shocked to death! (maybe you are interpreting or calculating the total panel needed as 400 amps versus each of the individual sockets or circuit breakers as 15 to 25 amps? Is this correct?) Now, as for wiring, if you were to use aluminium wiring in a home, that could be dangerous because aluminium heats up faster than copper and could cause major house fires from past experiences when aluminium was used. Furthermore, you will need to know the impedance and resistance formulas for the length of wire in question that you will be installing. I would recommend a chart to reference your meter to Ohm's Law with and you will need to know how to wire your panels with step down transformers that handle the particular alternating current in question at the correct phases for whatever it is that this person needs 400 amps for! This sounds like something more industrial than home based. I almost missed your AWG part of the question- AWG is a system for indicating wire diameter size- you can type this in on the interent through a search and it should bring up tables for your reference- I beleive the smaller the AWG, the larger the diameter of the wire, and vice versa. You should also do a search and download an electrical engineer's handbook or consider purchasing one.

Answer 4

What's he got? An Electric chair in the basement?