Ask Me Help Desk - Adding subpanel

I have a 200A main panel in my garage and want to install a subpanel in my basement to feed 4 circuits (15 & 20 A). The best route I can find for the feeder wire is through the garage in conduit, then entering the basement through the concrete foundation. I have a couple of questions.

1. If I install a 100A main panel to use as my subpanel, then just use a 60A feeder breaker to supply it, in the end it's a 60A subpanel, correct?

2. What type/size wire should I use to feed the subpanel? (Assuming a 60A "feeder breaker" and a run of about 45')

2. What type/size of conduit should I use?

3. Any suggestions on how to handle the wiring at the point where I have to pass through the concrete foundation? To clarify, the floor in my garage is about a foot below the top of the foundation wall. So, I can drill directly through the wall into the basement. The problem is going to be drilling a large enough hole for the conduit. The subpanel will be located about 2 feet directly below where I pass through the foundation wall.

Thanks for any advice.

1. Yes the sub is now only rated at 60 amps,subject to derating 80%, so actually 48 amp load is the max.

2.If you can do the entire run with conduit. Then use 3#6 stranded THHN/THWN rated each one colored black, red, and white, and 1#10 green.

3.1 inch PVC Schedule 40 is easy to install. There quite a few parts needed, but layout, measure, cut, and glue is basically the chore. Or you can use 1- 4 wire #4 SER Aluminum cable,the only issue with AL wire is to be sure the connections are done properly using anti oxidant compound. Bending PVC conduit, uses heat, is another whole discussion, let me know if you need to know.

4.My guess is there is drywall on the upper wall, that ends at the concrete. IF so the bottom approx 12 inch is a the wood framing of the floor over that basement. Look in the basement you are heading the wire to, and note the framing, may be anything from 8" to 12" joists. You should be able to easiy drill through this wood.

Be sure to isolate the neutral and the equipment ground at the sub panel, including all branch wiring.

Thanks for the advice. I checked and, as you suggested, I can enter the basement through a floor joist rather than the concrete.

I think I will use the PVC conduit like you suggest. Can you describe how to heat and bend the PVC? I'll use fittings for all the connections and turns but there is a "jog" in the wall I'd rather just bend around. Where the 3rd stall meets the main garage, the 3rd stall wall is about 2" deeper than the main garage wall. As the conduit runs along the wall, it will need to go around that 2" and I figured on a long straight like that, a jog in the conduit (heat/bend) would be the best idea.

Thanks again.

Quote:

Originally Posted by tkrussell

Be sure to isolate the neutral and the equipment ground at the sub panel, including all branch wiring.

Do you mean to separate neutral and ground wiring on their own respective bus bars? Sorry, it's probably clear as day but I'd rather ask than be surprised when I go to wire up the subpanel. I bought a "main lug" panel rather than a full blown main panel. Will I need to purchase something further for the panel?

Thanks again.

The panel will come with a neutral bar, you will also need an equipment ground bar.This will bolt directly to the panel's backbox.The panel may come with one, if not you need to buy it separately.

All the branch circuit neutrals (white wires) will go the neutral bar, which is insulated from the panel backbox. The panel may come with a green screw or a jumper wire. Do not use either. They are intended to bond the neutral bar only if the panel is a main panel.

Any green or bare wires coming back from the house circuits will need to go onto the equipment bar.
Hope this helps to claify. Get back if you have anymore questions.

Ok, I picked up a Siemens main lug panel (convertible to main panel). Anyway, it has a grounding bar attached directly to the panel along one side. It also has 2 neutral bars on either side of where the breakers install and those are isolated from the panel by the plastic frame that holds all the components together. It looks like a main panel without the main breaker. Does my description of the ground and neutral bars make sense and is that what you were referring to?

There is a large green screw at the top of one of the neutral bars. A sticker in the box says to torque that screw to bond the neutral (I'm reciting from memory and don't recall exactly what it said). I'm thinking that I want to remove that screw and that it is only there if you were to convert the panel to a "main panel" in which case you would want the neutral bars to have a connection to the panel itself (bonded?). Is this correct?

Quote:

Originally Posted by tkrussell

The panel will come with a neutral bar, you will also need an equipment ground bar.This will bolt directly to the panel's backbox.The panel may come with one, if not you need to buy it separately.

All the branch circuit neutrals (white wires) will go the the neutral bar, which is insulated from the panel backbox. The panel may come with a green screw or a jumper wire. Do not use either. They are intended to bond the neutral bar only if the panel is a main panel.

Any green or bare wires coming back from the house circuits will need to go onto the equipment bar.
Hope this helps to claify. Get back if you have anymore questions.

Quote:

Originally Posted by Augy123

Ok, I picked up a Siemens main lug panel (convertible to main panel). Anyway, it has a grounding bar attached directly to the panel along one side. It also has 2 neutral bars on either side of where the breakers install and those are isolated from the panel by the plastic frame that holds all the components together. It looks like a main panel without the main breaker. Does my description of the ground and neutral bars make sense and is that what you were refering to?

There is a large green screw at the top of one of the neutral bars. A sticker in the box says to torque that screw to bond the neutral (I'm reciting from memory and don't recall exactly what it said). I'm thinking that I want to remove that screw and that it is only there if you were to convert the panel to a "main panel" in which case you would want the neutral bars to have a connection to the panel itself (bonded?). Is this correct?

This is correct and TK will echo this when he next gets on board.