Mike M wrote:
>Where I am we have NEC, state, and then local rules, not to mention
>sometimes building code or fire marshalls. Arguing with inspectors is
>a little like wallowing in the mud with pigs. Eventually you figure
>out they like it. LOL, and usually they can cite the code section.
I agree, but the *code* they cite isn't always in the books...
In my town the inspector was busting my gonads about building a simple
shed, and he was using some interesting *interpretations* of state code.
So when I copied the code from the book and then called the state and
made a recording of the official telling me the inspector cannot
supersede state code on that matter (and played it for him), he
relented. But I'm wary of what he will do upon final inspection of the
site - these guys tend to have long (and mean) memories.
In another town when we had an inspection of the new breaker panel
replacement in my mother's house, the town electrical inspector insisted
we pay for a plumbing permit and refused to sign off on the electrical
inspection. He was looking at a short piece of PVC that was used as a
drain from the furnace's humidifier down to the sump (this was on the
other side of the basement, no connection to the electrical work). That
installation was from more than 20 years ago, and since mom died we
couldn't ask her for the copy of the paper work from the contractor for
the installation, so the inspector said we could not have a C.O. for the
These guys are just plain evil.
brianlanning, or somebody so disguised, wrote the following at or about
4/19/2006 11:38 AM:
Probably just to give you a margin of "safety" so you're not continually
popping the main breaker.
60 Main and 6 or less 15a breakers. How likely is it that you'll have a
10a+ load on six of them at the same time? Low, I'd say.
60A Main and, say, 12 breakers (mixed bag of 15A and 20A) much more
likely to pop the main.
Not a safety issue, per se, more like a "this standard is engineered for
the dumbest person." Think "I still have breakers and open outlets.
How can I possibly overload this panel?"
The financial corollary would be, "I can't be overdrawn! I still have
checks in my checkbook!"<g>
I think we are interested in the STANDARDS here. From that one can determine
if he might get away with a higher gauge number on the wire or six 40AMP
breakers in the sub-panel knowing how far he is straying from what the EE's
recommend and building inspectors demand.
I ran #8 24' or more from my panel to my stove/oven as I recall so #6
sounded a bit conservative from my perspective.
But I always check the code requirements before installing or replacing
electric runs or panels and try to follow the standards or better during
Experience taught me that it is cheaper to do it "bullet proof" during the
installation than to retrofit subsequently.
Having said all that, he standards allow for quite a lot. But, then, the
house across the street burned down after some faulty electrical work by a
Telling the Fireman you figured you could get away with a cheaper breaker
box is not the conversation I want to have.
First, remove the bonding screw that bonds the grounded (neutral)
busbar to the enclosure. Second, purchase an accessory busbar and
fasten it to the enclosure as the grounding busbar. Third, bond the
grounding busbar in the subpanel to the grounding busbar in the
service entrance with the appropriate gauge green/bare conductor. You'll
also want to bond the grounded busbar in the subpanel to the grounded
busbar in the service entrance panel with suitably sized white conductor.
Not a problem.
If you use a 60A breaker, #6 should be sufficient at that length. Check
the NEC tables for definitive value based upon your conductor temperature
Are you using conduit and a thermoplastic insulated 90 degree-rated conductor
such as THHN or #6/3 w/g jacketed (which IIRC are 60 degree-rated conductors)?
No - you should run 4 - two hots, a neutral and a ground.
Because the cost difference isn't much, I'd recommend you go with #4 in
case you ever want to upgrade from the 60A to 100A. Also, be sure to
use large enough conduit (probably 2") so that you don't overfill.
Lots of other good responses here.
Lastly, do talk to your electrical inspector - not only is it the law
(almost everywhere) but it means you'll have a safe install and you
won't be on the line if your house burns down and it is traced back to
your work! Our local inspector is very helpful and is happy to help
I think there is a choice here. He can run 4 wires as you say, keeping
ground and neutral separate in the subpanel, or he can run 3 wires
and put a grounding rod in at the outbuilding with a bonded ground
bus in the subpanel. I don't remember if there is some minimum
distance between buildings for that.
As others have suggested, I'd talk to the local inspector to see
what he/she expects. My local inspectors are generally very helpful
if you talk to them in advance.
The screw that fastens the grounding busbar to the subpanel enclosure
serves as a bonding screw. Discard the bonding screw you remove from
the grounded busbar in the subpanel.
If you're burying the conduit, there is really no good reason to use
jacketed cable rather than individual conductors. Run four THHN or THW
- #6 or #4 BLACK (current carrying conductor #1)
- #6 or #4 RED (current carrying conductor #2)
- #6 or #4 WHITE (grounded conductor, aka neutral)
- #8 or #6 GREEN (grounding conductor)
RED and BLACK are simply convention, you can use any color other
than white, green or green with yellow stripes for the current
carrying conductors. The RED and BLACK conductors must, of course,
be connected to different poles in the service entrance via a two-pole
Watch your conduit fill percentage. 2" should be more than sufficient
as only two of the four conductors in the conduit carry current.
robb email@example.com wrote:
> I have a new SquareD load center panel (QO8-16L100S) that I
> want to use but need some clarification.
> 1. This particular panel only has one grounding/neutral bar, but I was
> under the impression the ground and neutral must be separated in a
> subpanel installed in a stand alone structure.
Buy a separate ground bar kit from a SQ D distributor and install it.
> 2. The panel is rated for 100A, but I was hoping to use a 60A-75A
> breaker in the main box to feed this subpanel. Is this a problem?
No. Just install a 2P-60 as a main C/B the in the sub panel.
> 3. The run from the main panel to the sub will only be about 15 ft.
> total. What size wire do you suggest I run?
Bigger is better.
I'd run #2 but #4 will do the job.
Since my profession is a "catastrophe" insurance adjuster, may I suggest if
you live in an area that doesn't have a-holes for inspectors, get a permit &
have it inspected. Should your workshop burn due to an electrical problem
some of the insurance companies will try to use "your" contributory
negligence to gain a little wiggle room. Also take pictures of your work and
do a diagram with materials used. Keep receipts. It's not often, but some
adjusters will push on you to accept less in fear that a battle will yield
nothing . . . just my two cents . . . Also always keep your agent up to
date on any new out buildings and their content in $$$$$. . . . Most home
owner policies only give you 10% on all out buildings combined. That's 10%
of your total home owners value. $300,00.00 home, you have $30,000.00
coverage on out buildings . . . If your shop is attached to the home, ie . .
garage, that does not apply . . . Also, if you sell anything out of your
home shop, make sure you incorporate the work "STUDIO" as in art into the
business name . . . . Home being used for business purposes nulls your
coverage in most cases . . . .
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