Installing a subpanel

I currently have an 200amp panel with only one open space and I am in the process of finishing the basement. I was looking to install an 125 amp subpanel with 8 spaces (16 circuits) to use for the basement and future outdoor projects including a hot tube.

Will this size subpanel do and what size wires should I use to feed it from the main panel?

Will I need to run a new ground wire for the subpanel to the water pipe or can I extend the ground and neutral hook ups from the main panel to the subpanel?

The subpanel will be a couple of feet away from the main panel.

Thanks for the help.

 

Give us a layout, and quantity, of what electrical stuff you plan to install in the finished basement.

How many light fixtures and wattage of each. How many receptacles?

A hot tub require's a 50 amp circuit at the most, that's all I've seen anyway. Somebody chime in if I'm incorrect.

The subpanel will require four wires: 2-hots, 1-grounded (neutral) and 1-equipment grounding.

You'll need two terminal bars in the subpanel one for the grounded conductor (neutral) and one for the equipment grounding conductor.

The grounded conductor (neutral) connection has to be isolated from the panel (not bonded to it).

The equipment grounding conductor is bonded to the subpanel.

NO ground rod(s) required because the subpanel is in the same structure as the service panel.

 

The subpanel that you install should have as many spaces as you can get. Most folks run out of spaces, before they run out of capacity (as you have found). The incremental cost is small.

 

Thanks thinman

Layout:

Lights will be about 60 watts.

Office - Will have several computers and probably one light fixture plus track lighting (not much). Will have a lot of outlets for all the computer stuff so I will have this room on its on circuit.

Kids room - One light and four outlets

Workout room(yeah right!!) - one light and three outlets

TV room - Will probably have its own circuit since I will have the home theater systems in there plus recess lighting and some column lighting and maybe some other goodies in the future

Full Bathroom - One light and one gfi outlet

Party area - Probably have a small refrigerator, 6-8 outlets, 9 - 12 recess lighting

small storage area - one light

Outside future projects - Hot Tube and pond

Thanks Ron.

Our neighbor which has the same house got a panel with 40 spaces but we only got 20 spaces.

 

For this 125A subpanel I would suggest #1 awg copper or 2/0awg al. Four conductors, two hot, one grounded (neutral) and one grounding.

 

I think a 100 amp circuit would be sufficient in your case.

Install a 100 amp circuit breaker in the service panel and use #3 awg copper (if #3 is unavailable, use #2 awg copper) or #1 awg aluminum for the ungrounded conductors (hot wires).

Number #6 awg copper or #4 awg aluminum for the grounded conductor (neutral). Those wires would be able to handle 65 amps between any one hot conductor and the grounded (neutral)conductor (120 volt).

The equipment grounding conductor's ampacity is based on the 100 amp circuit breaker and it would be a #8 awg copper or #6 awg aluminum.

These wire sizes are based on using single conductors within a raceway, not multiconductor cable.

The grounded and equipment grounding conductors will be connected to the same buss bar in the service panel. Some service panels have a jumper that connects two buss bars together. If that's would your panel is like, you can connect the grounded and equipment grounding conductor to separate buss bars.

You DON'T ground the water pipe to the subpanel. That's only allowed in the service panel.

Receptacles shall be installed so that no point measured horizontally along the floor line in any wall space is more than 6 feet from a receptacle outlet. This means you cannot exceed 12 feet between receptacles.

 

In my opinion, 100 amps is way more than you need (since you do not plan a shop or a kitchen in the basement). 60 amps would be plenty, and there's a pretty good chance that 40 or 50 amps would also do. I don't see any energy hogs in your list.

One important piece of information that would be useful is the square footage of your basement. If your basement is under 1200 square feet, I'd just go with 6/3 cable and a 60-amp breaker. I just can't see you ever using more than that. (Even with more than 1200 square feet, 60 amps is probably plenty.)

 

thinman,
Since this is a subpanel, and not directly fed by the main disconnect, just a feeder breaker in the main panel, I would suggest #1 cu or 1/0 al for a 100A panel. This is from table 310.16, 60 degree column (not 310.15). 110.14 would require 60 degree column 100A and less.

 

There's a lot of weasel words in 110.14. It is true that you can only use the 60-degree column if the terminations don't specify otherwise. However, 110.14(C)(1)(a)(3) says you can use the higher temperature rating if the terminations are listed as 75-degree terminations.

So if the breaker and panel both say that they have 75 degree terminations, then you can use the 75 degree column. If one or the other doesn't specify, you must use the 60 degree column.

 

Im not sure if you saw this John, but he mentioned a hot tub and future loads in his first post.

In my opinion, since the subpanel is only a few feet away, go big. Heck, you could even stick a 200a main lug panel in there and feed it with a 125a breaker. Im a big fan of over-building things.

 

I like marcerrin's thinking. As I mentioned early, my neighbor with the same house has a 40 space panel which is just about full and he finished his basement, has a pond, and is now getting a pool and he is going to need to get a subpanel.

I know we are not getting a pool but I do like to do projects around the house so I go to go big just to make sure.

 

marcerrin, you're right! I misread this post badly. I not only missed the hot tub, I missed the fact that the subpanel is only a few feet away.

Never mind ...

 

110.14 Electrical connections under the section for #14 awg to #1 awg conductors for circuits rated 100 amps of less states in (1) (3); Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors.

This tells me that a panelboard w/ dual rated temperature connections, 60 deg c/75 deg c, the conductors can be based on the 75 deg c column in table 310.16? All modern day electrical temperature terminations are dual rated for 60/75 deg c.