Determining Main Panel Load With Subpanel Added - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Determining Main Panel Load with Subpanel added
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04-11-2008, 11:15 AM   #1
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## Determining Main Panel Load with Subpanel added

Discussion in another thread got me thinking about a very important consideration when adding a subpanel to a main panel:

When adding a subpanel, does the load for the MAIN panel become the sum of the loads of both panels or is it calculated differently?
LOAD=Main+Sub
What if additional subpanels are added?

It seems that if you are adding subpanel to a MAIN because the MAIN is full, you would be taxing the load capacity of the main panel if you also filled the subpanel.

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 04-11-2008, 01:13 PM #2 Electrician   Join Date: Nov 2005 Location: Winnipeg, Manitoba Posts: 1,389 Rewards Points: 984 You will not be overloading your main panel, your main panel would draw only as much as your main breaker can handle. If your main panel is full and you add another subpanel, as long as you don't go over the rateing of the main breaker you are fine. You could have a full main panel as well as 10 subpanels that are all full but as long as you don't exceed the main breaker you will have no problems.
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04-11-2008, 01:21 PM   #3
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Quote:
 Originally Posted by Randell Tarin When adding a subpanel, does the load for the MAIN panel become the sum of the loads of both panels or is it calculated differently?LOAD=Main+Sub What if additional subpanels are added?
You are correct. If you are doing a load calculation for your service, you would add the service panel (main) loads plus the sub panel loads from all sub panels. Note, we are talking about actual loads and not merely adding up the sums of all branch over current devises.

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