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lonnierogers 12-25-2010 11:39 AM

Adding a subpanel
 
I have an outdoor 200 amp main breaker panel with 24 breaker spaces, I have a 8 space subpanel attached to it. We are fixing to add a wall oven to the kitchen and I am needing to upgrade the subpanel as I am out of breaker spaces. I am wondering do I need to get another 200 amp breaker box with a main breaker or can I use a 125 amp breaker box as my new subpanel?

My cousin who is a licensed electrician will be doing the work for me but he is on vacation in Montana at the moment and I would like to get all the stuff together for when he comes back.

Thank You in advance for any help suggested.

Lonnie Rogers

rjniles 12-25-2010 12:33 PM

Yes you can have a 125 amp sub off a 200 amp main.

Just an idea for you, if you have the space in the outside panel, you could run to the outside for your new oven and leave the existing sub panel alone.

lonnierogers 12-25-2010 01:07 PM

Quote:

Originally Posted by rjniles
Yes you can have a 125 amp sub off a 200 amp main.

Just an idea for you, if you have the space in the outside panel, you could run to the outside for your new oven and leave the existing sub panel alone.

We don't have an inside panel, our main box has 20 something spaces and the subpanel we have now is only 8 spaces and all the spaces are full. We needed to use two big boxes when we resided the house but couldn't afford two of them. Do we need to have a main breaker in the replacement box as well as the main box?

rjniles 12-25-2010 01:40 PM

You do not need a breaker in the sub panel (as long as they are in the same building). The sub must have a breaker in the main panel.

That being said: I prefer having a breaker in the sub. Usually you can buy a 100 amp panel with a main breaker and 5 20 amp single pole breakers as a package in one of the big box stores much cheaper that buying the parts individually. I was at :The Big Orange the other day and a GE 100 amp panel, with a main breaker and 5 - 20 amp single poles, was about $75.

lonnierogers 12-25-2010 01:52 PM

Ok. I will get the 125 amp sub panel they have at home depot. I already have a bunch of breakers that were given to me by my cousin. Thank you for the advice. Just a side note we are powering the subpanel by a direct feed from the main box via the bottom rail tap. This won't change anything will it? As far as having a main disconnect in both boxes? It doesn't seem as it should make a difference but I'm just knowledgeable to know the black wire goes on the gold screw and the white goes on the silver and the copper goes on the back (that's what family is for).

rjniles 12-25-2010 02:56 PM

Quote:

Originally Posted by lonnierogers (Post 556789)
Ok. I will get the 125 amp sub panel they have at home depot. I already have a bunch of breakers that were given to me by my cousin. Thank you for the advice. Just a side note we are powering the subpanel by a direct feed from the main box via the bottom rail tap. This won't change anything will it? As far as having a main disconnect in both boxes? It doesn't seem as it should make a difference but I'm just knowledgeable to know the black wire goes on the gold screw and the white goes on the silver and the copper goes on the back (that's what family is for).

No you can not feed off the feed thru lugs at the bottom of the panel unless you size the wiring to the sub for 200 amps and use a rated 200 amp panel as the sub(same as main breaker). It is cheaper to feed off a breaker in the main and size your wiring based on your requiremments for the sub panel. You can use the 100 amp breaker in the sub panel even if the supply breaker (and wiring) in the main has less amperacity. Since you have an existing sub planel I assumed it is has a breaker in the main that you can replace. If it does not, free up 2 slots in the main by rewiring the circuits to your new sub panel.

lonnierogers 12-25-2010 04:25 PM

Gotcha. Thank you for the advice. I will have to go shopping now.

kbsparky 12-25-2010 06:16 PM

Quote:

Originally Posted by rjniles (Post 556803)
No you can not feed off the feed thru lugs at the bottom of the panel unless you size the wiring to the sub for 200 amps and use a rated 200 amp panel as the sub(same as main breaker)....

Not quite 100% true. IF the sub-panel is mounted adjacent to the main one, AND connected with conduit, AND has a main breaker in it, THEN one can invoke the tap conductor rules and safely connect a smaller wire to those feed-thru lugs. As long as those conductors are sized to handle the max load of the sub-panel's main breaker.

In this example, one would only need to connect at least a #1 copper or #2/0 Aluminum wire instead of a larger one.


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