Clarification on Article 220.83(B)

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wmeek

Senior Member
Location
Texas
Occupation
Electrician
I was wanting to verify the interpretation of 220.83(B). I am adding a water heater, A/C, elect. heat, Refrigerator, Keg Cooler in a room above a garage 14'x39'. Also adding an air compressor in the 20' X40' garage downstairs. Also will be adding 3va per square foot per 220.12. Article 220.83 says to take 100% of the largest load of A/C or Electric Heat. Then it says to take the first 8000kva at 100%, and the remainder of all other loads at 40%. My question is do you take all the loads from existing dwelling and add all your loads from new addition, and take 8000kva at 100%and the remainder at 40% to find out if existing service is adequate to serve the new loads. I am just trying to make sure if I am interpreting this code section correctly.
 
Looks to me like you use the formula in 220.83 (B) for the new and existing together. So you would take all the calculated other loads including existing and new, and take the first 8kva of that at 100% and the remainder at 40% then add that to 100% of the largest a/c-heat load, 100% of the air comp.
 
Thank you for your input on 220.83. I think I am on the right track. Was wandering why would the air compressor be at 100%. It is cord and plug connected. I would think it would be treated as an appliance on a dedicated circuit. I also Have a Pool Pump motor on existing dwelling, would it have to be at 100% also.
 
Thanks again for all your help. I just have not done a calculation that pertained to article 220.83. What I have is a dwelling with a 125A Service and a customer that wants to add a game room in a room above a detatched garage. I came up with 165.28 Amps, and will have to upgrade the existing service to a 200A.
Again Thanks Alot
 
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