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Discussion Starter · #1 ·
I have a customer who has a double wide trailer and two other outbuildings on the same piece of property. The trailer is powered from the meter pack which has space for other breakers. Right now it has two other 125A double pole breakers which serve the other two buildings. Is there anything wrong with this?

How do you do a load calculation for three separate buildings that all use the same service? Is this even acceptable? I don't know of anything that would prohibit it.

This is what I did so far. I combined the calculations for the three separate buildings into one calculation and came up with a required service size which exceeds the size of the existing service. - I would however, like some confirmation that I am approaching this correctly.
 

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Discussion Starter · #3 · (Edited)
The house would be calculated as a dwelling. You then need to calculate the other buildings based on use and load unless they are also dwellings
One building is a dwelling, the other additional building is a tool shop. (there is also an additional well house that I did not mention at first.)
How would you categorize a shop?
 

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This is how almost all rural areas here are set up.look around ask some questions about expansion and go from there a lot of small rural buildings are rarely used.
 

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Have you read 220.87? It allows you to use the power company maximum demand for the last year instead of doing a load calc. Or you can put a recording ammeter on the service for at least 30 days.

Coincidentally, we're having the Fluke rep stop by our shop next Tuesday to show us some recording ammeters. We have a customer that keeps adding large motor loads to some existing MCC's and we figured it's time to get one.
 

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I have a customer who has a double wide trailer and two other outbuildings on the same piece of property. The trailer is powered from the meter pack which has space for other breakers. Right now it has two other 125A double pole breakers which serve the other two buildings. Is there anything wrong with this?

How do you do a load calculation for three separate buildings that all use the same service? Is this even acceptable? I don't know of anything that would prohibit it.

This is what I did so far. I combined the calculations for the three separate buildings into one calculation and came up with a required service size which exceeds the size of the existing service. - I would however, like some confirmation that I am approaching this correctly.
Just curious, but if these are existing and are powered already, why do you need to do a load calculation? Are you needing to add something substantial to the service?

Anyway, you would do the mobile home according to Article 550 and the other dwelling according to Article 220 if it's not a mobile home.

The other building according to existing load.
 

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Discussion Starter · #8 · (Edited)
He bought this piece of property as is and I don't think he realized that some of the buildings were probably built without permits. He is going to be doing a lot of electrical work out there in addition to what he wants me to do, but I'm not going to do anything without a permit.... (too much work and liability for that) the existing service is missing a dead front and is in rough shape. Someone also stole the electrical panel out of his shop. I know once I buy a permit and get an inspector out there all these issues are going to come up.... if we replace the service and find out it is too small we wasted our money.... Hey thanks for the great answer! I'll have to check out article 550. I really do appreciate the input, I learn more and more as I go.
 
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