100Amp main sub panel to granny flat 100amp?


Old 11-06-18, 02:34 PM
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100Amp main sub panel to granny flat 100amp?


We are building a granny flat on our property. We have a 2100 square foot home with a 100Amp panel all the spots are maxed out (doubled). The plans for the granny flat call for a 100amp sub panel. We were hoping to upgrade our home to a 200amp panel. We now realized that the transformer is across the street from us. We think the amp wire that comes across the street is 100. Does anyone have a suggestion on what to do? We called our locate electric company and they are 7 weeks out from coming to tell us what runs to our main home.

Old 11-06-18, 03:50 PM
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Welcome to the forums.

I'm quite sure your service drop is 100A and the poco... in most cases... will not increase it with a 200A service upgrade at your home.

The power companies don't follow the same electrical codes that your house does. They are allowed to use that 100A cable to supply a 200A service due to the cable is hanging in free air.
Old 11-06-18, 05:06 PM
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You might also be able to have a separate service and meter connect to the flat if it is a separate unattached building.
Old 11-08-18, 06:12 AM
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Usually you need a separate permit to install a new service panel and service entrance.

A licensed electrician is recommended if not required for this portion of the work.

If your city inspector will okay the 200 amp panel and the power company will pull/replace the meter for the project then just go ahead and have the new 200 amp panel installed notwithstanding the 100 amp service drop.

You can install the 100 amp subpanel and do all of the interior wiring at your leisure using a separate permit.
Old 11-08-18, 10:16 AM
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In most areas the service drop cable from the pole to the house is not your responsibility. The power company will choose to replace it or not (probably not) when they get the paperwork from your service upgrade permit. As PJ mentioned, aerial cables can carry much higher loads due to the cooling that air circulation provides; so the power company runs more amps through smaller wires than is allowed inside a building.

They also know that unless you are installing a massive electrical load like an on demand water heater, the actual continuous electrical usage in your MiL apartment will be very small so it's not worth the expense to upsize the wire.

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