Residential standby generator sizing

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Big Guns

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Hello, I have an 8,000 square foot house with a 400 amp service along with two 200 amp panels one panel is on the oppsite side of wall where the 400 amp meter is located and the other is on the other side of house in garage. The house is split up in both panels so it would be very costly to seperate priority circuits. So first question of my 2 part questions is can I bug my service entrance cable in my meter can and feed my 400 amp ATS which would be installed right next to existing meter can, is this code compliant. My second question is without me getting exact loads for all mechanicals and appliance and i want to cover whole house with generator what size would i need to do so. thank you
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
You can only feed the ATS directly from the meter IF the ATS is SERVICE RATED. (It will have service OCP device built in if it is)
If the ATS is service rated, the generator would need to be sized to the load being switched.
If the generator does not have that full capacity, it is possible to install load shed devices to drop sufficient loads.
 

echerbst

Member
Location
chicago
You would need to use a 400 amp service rates transfer switch then your 200 panels become sub panels. I you wanted full house coverage without load sheeding gonna need a big unit. How many a/c units, electric or gas heat, range, well, dryer. Those are your big loads. Would say 30-40kw for whole house and could get away with 20kw with load sheeding if on gas.
 
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