subpanel selection

[mattmeitzner]

I went to Lowe's today and discovered that it might actually be a break even proposition to install a subpanel instead of running 6 new circuits back to the main, since i'll avoid about 150 total feet (over

6 circuits) of 12/2 cable. However, I saw only 100Amp, 125Amp, and 200Amp panels for sale. I was thinking I could find a 60A panel. One of the 100A panels came in a contractor pack with the ground bar, 4 20A breakers, and one 30A double breaker for real cheap. So my question is whether I can just buy a 100A panel, and connect it to a 40A or 60A breaker in the main panel, thereby effectively limiting it to 60A. If I buy a main lug panel, do I then just connect the #6 or #4 wires (depending on the amperage I choose) to the main lugs on the subpanel? If I buy a main breaker panel, is it just the lower of the two breaker amperages from the main or sub panel that determines the rating of the subpanel, or is that a no-no?

If I choose to just run 6 new circuits back to the main panel and dispense with the sub altogether, can I run all 6 through one hole in the studs, or would there be interference or some other bad result? Do I need to drill multiple holes in the studs to make the run back to the main panel?

Thanks

[RBM]

The panel's buss determines its amperage rating. It is fine to use a 100 amp panel and feed it with a 40 or 60 amp feeder. You don't need a main breaker in the sub,You would connect to the main lugs, but if you find it cheaper to buy a panel with one, it's fine, the breaker feeding the sub will be the one protecting the feeder, so it doesn't matter that the panel may have a 100 amp breaker in it. Just be sure to separate the neutral from the ground buss, and do not install the bonding screw

[Tom Horne]

What you propose to do is perfectly acceptable practice. The larger main breaker in the feeder supplied panel becomes a disconnect just as if you had installed an enclosed switch that some manufactures offer in a breaker style housing for use in isolating feeders from back feeds or complying with double block and break safety requirements in some safe work practices policies. You do have to do a calculation of the load to be served to be sure that the over current protective device and the feeder conductors are large enough to carry the calculated load. It is perfectly acceptable to terminate the feeder conductors on the main lugs of a main lug only (MLO) panel. The rating of the panel is determined by it's listing and labeling. Using the panel at any amperage at or below its listing is fine.

If you run all six cables through the same hole then you will exceed the de-rated amperage of the cables conductors. Shooting from the hip I believe you can get by with three two wire cables in the same hole. I would just buy the four conductor plus ground two circuit cable to make pulling easier and run each two circuit cable in it's own hole.

-- Tom Horne,

"This alternating current stuff is just a fad it is much too dangerous for general use." Thomas Alva Edison

[Toller]

Let me just add that you would have to be crazy to run 6 separate circuits when you could run a subpanel instead. The labor savings will cover the extra $50 real fast; not to mention the voltage drop reduction if you use an adequate cable. What are you doing that you need 6 circuits?

[mattmeitzner]

I'm finishing my basement. I will be using 2 circuits for lights (about 15-16 lights total), 1 for outlets, 1 for sewage pump, 1 for bathroom GFI outlet, and 1 for general other stuff (e.g, bathroom exhaust fan). If there's a better way, please let me know. I'm leaning the way of the subpanel now, but I'm going to be doing everything myself, provided the electrical permit I pulled already can be amended to include the subpanel to replace the longer home runs. So since I'm doing it myself, there's no real "Labor savings", other than my own time. Thanks again!

[Phisherman]

Try to have at least one electrical outlet on another circuit. Or, you can "leap-frog" outlets so that every other one is connected to the same circuit. My basement circuits are GFI, except for my 220v circuit. Put your subpanel box centrally located, preferably inside a closet or out-of-sight yet easily accessible. Electrical panels are ugly! Best to err on the side of too many outlets than not enough.

[Toller]

That seems reasonable. If you wanted to economize on circuits you could put half the outlets on each lighting circuit (15 sounds like an awful lot of lights...) and put the exhaust fan on the bathroom circuit. That would cut it to 4. But one nice thing about a subpanel is that you don't have to economize; 6 circuits isn't much more work than 4.

[HeyBub]

Paint the box white.

Put a large red cross and the legend "First Aid" on the outside.

You can pass TWO inspections that way.

[mattmeitzner]

Yeah, I know that's a lot of lights, but being a basement there's little to no natural light and everyone I talk to says to plan for

25-50% more light than I think I'll need. It's a big basement too - almost 700sqft of finished space when I'm done, and I also plan on using those compact fluorescent bulbs, whcih always seem a bit dimmer than their incandescent counterparts. I also need to have 11 outlets, so even with 12/2 wire, I can't get the lights and outlets all on two circuits, based on a 20amp breaker only being able to handle 12 devices, right? Then finally, I thought that the bathroom GFI outlet had to be on its own dedicated circuit...are you saying I can put the bath fan on that same line?

[RickH]

Thats what I did, got an 8 slot 100A panel and fed it with a 60A breaker. Just dont re-bond the neutral to ground in the subpanel, the new subpanel will be grounded through the conduit and neutral will "float" in. Rebonding the neutral will inadvertently make the ground between the 2 panels carry load and you dont want that.

[Toller]

At 20w each, 15 lights are only 300w. Why 2 circuits? You can have as many outlets or lights as you want on a circuit; the contraint is not overloading the circuit. But of course there is something to be said for having two lighting circuits in case of a trip. So if you have two lighting/outlet circuits, the lighting will take 2a, leaving 18a on each circuit for whatever you have to plug in. Unless you are doing something weird down there, you shouldn't exceed that. Unless something has changed since the 2002 NEC, you can put everything in a single bathroom on one circuit.

So yeah, 4 circuits should be adequate. A subpanel might be more elegant though; as well as making future expansion easier.

[Mark Lloyd]

My grandmother's had the panel in a garage. Later the garage was converted to a room. She hung a picture in front of the panel. The picture wasn't too hard to move if necessary.

BTW, that panel is a Square D.

As to the OP, I like the idea of using a subpanel.

[mattmeitzner]

Toller - to be honest, I'm just following the guidance of a "basement finishing manual" style book. In it, it states that no more than 10 current-drawing devices can be on a 14/2 (15A) circuit and no more than 12 devices on a 12/2 circuit. It also states that GFI outlets must be on their own circuit. The book was written in 2006. It sounds like that may not be the case based on your post and the referenced 2002 NEC. If you're right, I'd definitely go to 4 circuits

- 1 for half the lights and half the outlets, 1 for the other half, 1 for bathroom stuff, and 1 for the sewage pump. Probably do the subpanel still just for ease in the future.

Either way though, the permit I took out didn't specify that I'd be installing a subpanel. Actually it didn't state how I'd be connecting the circuits to power at all, but in the interest of not pissing off the electrical inspector, I think I'll ask him either way since he's really the opinion that matters. Thanks again though...

[Wayne Whitney]

Neither of these statements are correct for residential work. The restriction on receptacles may apply to commercial work. As to restriction on GFI outlets sharing a circuit with other loads, I'm aware of two:

The circuits serving the kitchen GFIs must at least two in number, and these circuits can only serve loads in the kitchen and dining room.

The circuit serving a bathroom GFI must meet one of two conditions: either it only serves loads in that bathroom, or it only serves bathroom GFIs.

Cheers, Wayne

[Toller]

Let us know what he says. His word is final regardless of what the NEC, your book, or anything else says.

[Paul Franklin]

One more consideration I haven't seen mentioned in this thread:

Regarding a MLO panel versus a panel with a main breaker: Isn't the rule that you have to be able to kill all loads connected to a panel with a maximum of 6 actions? If I'm remembering that right, the implication is that if a subpanel will have (or could have) more than load breakers, you have to use a main breaker so that all power can be killed with no more than 6 actions. I don't believe walking over the main panel and throwing the breaker feeding the sub counts.

Someone with better recollection of this rule chime in please, my code book is still packed somewhere....

Paul F.

[Wayne Whitney]

That requirement is for killing all the service conductors to a building, so it applies at the main disconnect. It doesn't apply for subpanels. It would apply for a feeder to a detached garage, which could terminate in a MLO panel as long as there are 6 or fewer breakers in it.

Cheers, Wayne

[hallerb]

two things around here ALL basement outlets must be GFCI protected. had big hassle with two different buyers at home sale time, I upgraded to GFCIs....

with basement space install some ingress egress windows which will not only add light and air but qualify the added space as bedrooms, very valuable when its time to sell!

[RBM]

The NEC does not require outlets in finished parts of a basement to be GFCI protected

[Tekkie®]

Phisherman posted for all of us...

DON'T put the sub panel in a closet!