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# Residential Service - Minimum Size?

#1
06-15-05, 11:44 AM
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Join Date: Jan 2005
Location: United States
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Residential Service - Minimum Size?

For a small house, I'm calculating the Electrical loads as follows:

1300 sq.ft. x 3 watts = 3900 watts
Dishwasher @ 1200 = 1200 watts
Disposal @ 800 = 800 watts
3 outdoor outlets @180 = 540 watts
---------------------------------------
6440 watts total

6440/230 = 28 amps

Does this mean that a 40 amp service would be sufficient?
Is there a minimum service size regardless of the calculation?

Note that this house has a Gas Range, Gas wall heater and a Gas Dryer. There is a Refrigerator/Freezer and a Microwave but no major fixed electrical appliances other than listed above.

#2
06-15-05, 11:56 AM
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" Is there a minimum service size regardless of the calculation? "

My city, it was 100 amp I think it went up to 125 amp.

#3
06-15-05, 02:52 PM
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Location: welland ontario
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You will not get insurance if the house has less than 100 amp service.

#4
06-15-05, 05:32 PM
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The National Electrical Code calls for a 100 amp minimum.

In your calculation you left out the 2 small appliance kitchen circuits and the laundry circuit.

#5
06-15-05, 09:12 PM
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Originally Posted by pcboss
The National Electrical Code calls for a 100 amp minimum.

In your calculation you left out the 2 small appliance kitchen circuits and the laundry circuit.
You're right so I add another 4500 watts. The calculation then results in a total of 10940 watts.

10940/230 = 48 amps

NEC minimum of 100 amp service or whatever the city requires will govern.

#6
06-16-05, 01:30 PM
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Location: Harrisonburg
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I have to tell you.....Regardless of the SQ Ft...in todays home we do not put in anything less than 200A service. Cost wise not that much of a difference between a 100A and a 200A service these days.....

With new homes their is always the possible need for expansion and so on and when it comes to figuring a smaller home...or firm simply always goes 200A or more if needed depending on the size of house we are doing.

Yes, the NEC says the service has to be 100A minimum so regardless of your calculations you need a 100A service minimum....but do the math and look at the 200A service panels......Home line or GE ( we use Square D QO ) but the homeline and GE brands are fine.

Now some will argue..I am sure but let me tell you.......we charge very close to the same for a 200A as we do a 100A.....of course we buy the 200A units larger amounts since we split them between my brother any myself...but still it has more options.

Just a thought......

#7
06-16-05, 01:53 PM
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I will absolutely concur about a 200 amp service. I can't remember the last time I did a 100 amp service.
We have many modest homes in the area that are all gas and can "get away" with 100 amps. With service replacements some do go this way, but not very many.

I always knew there was a 100 amp minimum service as per the NEC. I completely forget where it is in the book though. Who has the Art.# ?

#8
06-16-05, 02:08 PM
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Speedy.

We are still in the 1999 here in VA but it is Art. 230-79(c) for One-Family Dwellings.

Yeppers......I cant remember the last 100A unit we put in. Probably a sub-panel to a detached garage or something but in a house...heck it has been years....I have replaced quite a few...

#9
06-16-05, 02:52 PM
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Yup. That's what I was looking for. Thanks.