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?
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
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.
"This alternating current stuff is just a fad it is much too dangerous
for general use." Thomas Alva Edison
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
What are you doing that you need 6 circuits?
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!
On Fri, 02 Nov 2007 05:10:12 -0700, firstname.lastname@example.org wrote:
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.
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.
Just to close the loop, I submitted an electrical permit amendment
with the suggested wiring as suggested on this and other threads and
and it just came through as approved. Going to cost me an extra $75
for the permit, but I guess that's just for the additional inspection
work. Overall, I still think this is gonna SAVE me money since I'll
be running almost 175' of less 12/2 cable and the subpanel kit only
costs a few bucks more than buying the breakers separately (the kit
comes with 6 breakers).
Thanks for all your help.
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.
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?
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.
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...
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
On Nov 1, 9:01 pm, email@example.com wrote:
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.
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....
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