Sub-Panel Question


Old 02-10-09, 11:18 PM
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Sub-Panel Question

I have a house that is nearly 100yrs old and is a major fixer upper. When I got the house it was in the midst of a renovation. The previous owner had a contractor skip out on her with all the money and materials and left the house in a mess.

The panel inside the house was literally just hanging from the opening in the wall where it once was mounted. It had no door cover, no cable clamps for the incoming lines and looked very rusted on the outside. I recently replaced this panel with a Square D QO 100a panel that was almost identical to to the previous Square D panel, ensuring that I hooked everything up just as it was with the old one. One of the things I noticed on the old panel was that the grounds and neutrals were all connected to the same bus bars. I did not see any bonding screw or any indication that the bus bars were bonded to the panel or a seperate ground bus. Also, the incoming feed from the main panel on the outside of the house was a 3-wire feed (H-H-N) and this sub-panel does not have a main cut-off switch.

From what I've researched over the past few days, since this is a sub-panel, a 4-wire line should have been run from the main outside panel by whomever originally installed the old sub-panel.

Is this correct?

More Background Info:

Outside the house is a main panel next to the meter. From this outside main panel there are a total of 4 breakers, one of them being a 100A breaker feeding what I'm assuming is called a (correct me if I'm wrong on the terminology) the Sub-Panel or is it considered a Main Lug.

Anyways, this Sub-Panel in the house is what supplies power to 90% of the house.

So I guess my main questions are:

1) Is this panel I just replaced considered a sub-panel or a main lug?
2) Should I have the feed from the outside panel to the sub replaced with a 4-wire feed (H-H-N-G), and then install a ground bus bar in the sub-panel
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Old 02-11-09, 04:35 AM
Join Date: Jun 2008
Location: VA.
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Anything after the service equipment(your outside panel) is a subpanel. If a panel doesn't have a main breaker it is called a main lug panel.

So what you have is a main lug subpanel.
Yes, it requires a 4 wire feeder, and you'll need the ground bar so you can separate neutrals/grounds.
Old 02-11-09, 08:44 PM
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Excellent! Thanks for the response. That's what what I thought the answers would be, but wanted confirmation

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