Electrical Wiring in the Home/Adding a 220 volt circuit


I have a 100A service box (new house in 2001) and want to add a 240V circuit to the garage for a heater.  The existing box is full of tandem breakers except for one 120V slot.  Can I add a sub-panel and run the 220V circuit for the heater from that?  How do I get power from the main panel to the sub-panel?  What AWG cable is required from the main panel to the sub-panel?  The heater requirements are 240V 20A and has a 6-20P plug.


I did not realize they were still making houses in the 21st century with only 100 amp service. Yes, you can do that, but it still does not up the capacity of amperage. So, be careful you do not exceed the 100 amp capacity.

The size wire depends on the size of the breaker sub panel.

You will also need to move one of the circuits from the main box to the branch box to make room for the double pole breaker for the branch box.
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Electrical Wiring in the Home

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Bob Sponaugle


Just about any home wiring question. (not appliance repair) I have done all kinds of home wiring for myself, including adding a new breaker box, etc. Please, questions from North America only. Please be specific with details.

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