Sub panel queston

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  #1  
Old 02-10-13, 10:26 AM
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Sub panel queston

Own a modular home. In 2008, a new 200 amp panel replaced a 125 amp on the outside utility pole by the home. "We own pole". It has the meter and 20 breaker slots. Inside this 200 amp panel is 1 - 100 amp breaker that feeds the home panel, and a 60 amp breaker that feeds a 6 circuit main lug panel in a detached garage. The only draw from garage is door opener, and a couple plugs. Inside the home we have electric stove, hot water tank, dryer, washer, fridge, freezer, microwave, dshwasher. We have no issues with tripping breakers or dimming lights. My wife is asthmatic, and we want to add 2 window ac units this summer. One 15,000btu that is 120v and requires 20 amp, one on other end of home, 10,000btu 120v 20 amp. Both high efficiency, radial compressors. I will be running individual lines to them. I would like to add a 6 circuit main lug sub panel to the house fed also by the 200 amp panel. I would use a 70 amp breaker and #4 thhn in 1 1/2" conduit. I will put the stove, 2 ac lines, dryer, and washer circuits in it. Because this is a modular, upgrading the 8 year old 100 amp service is a hassel. I already have the #4 copper thhn wire also. A freebie. This would mean the 200 amp meter panel would have a 100amp breaker feeding the house main, 70amp breaker feeding the house sub panel, and 60amp breaker feeding the garage. Is this legal. Our usage never goes anywhere near 80% of any panel ratings, but I feel the AC units will be to much for the 100 amp home panel.
 
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  #2  
Old 02-10-13, 10:34 AM
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Make it a 90 amp breaker.
 
  #3  
Old 02-10-13, 12:01 PM
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Are you out of slots to add breakers to the main panel? If so check to see if your panel will accept the 2 circuit breakers. They look like a single breaker but have 2 screws allowing 2 circuits per breaker. Each circuit is protected to the rating of the breaker.

You could connect some of your outlet and lighting circuits to them to free up space for the AC breakers and run the 2 circuits into the house through the conduit.

No sub panel, nor rerouting cables for the dryer, stove etc to the subpanel.

A much easier and less expensive way IMO. Only drawback is you don't have a use for that freebie THNN

Oversize your conduit and leave a pull string in it for possible future additions
 
  #4  
Old 02-10-13, 12:26 PM
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By code you may only have one feeder to a building.

Your only options are to try adding the loads and hope for the best, or upgrade the service to the house.
 
  #5  
Old 02-10-13, 03:16 PM
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I have 100A service with all the major loads you described plus central ac and have never tripped the main breaker.

My stove and cooktop are not the newer models that require a 40A breaker and my freezer is only a 4 cu ft chest model that only uses 1 amp while running. Yours may or may not hog more power.

The worst that can happen is you trip the main, but I don't see it happening unless you got everything big going at once which is unlikely. If it does trip, just don't run the ac while cooking, or fire up the grill instead of the stove.
 
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