yet another subpanel question

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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. >Mike
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 house.
These guys are just plain evil.
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For a service entrance, yes. If you maintain that the rule applies to subpanels as well, please cite the relevant article and section of the Code.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Sun, 23 Apr 2006 01:49:11 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Also when you are serving a second building on the same service. 225.33
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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>
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...but the 60A feed would be 240V (two legs of 120V), so it has the capacity of handling 120A of 120V IF it is balanced between the two legs....

...not if each breaker is running at 10A and they are balanced between the two 120V feeds. Once you get beyond that (up to the 15 or 20A values on the breakers...) it's time to stand back.

Make 'em all 30A breakers 'cause they keep popping the 15A ones, and see if you can get everything running and pop the main breaker before one of the circuits burns down the house. :-)

...or "what do you mean the check bounced? There was room for all those zeroes on the line for the amount!"
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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 installation.
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 licensed electrician.
Telling the Fireman you figured you could get away with a cheaper breaker box is not the conversation I want to have.

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Thanks to all for the quick responses. This was the exact info I was looking for. Now I'm off to see if home depot or lowe's carry #4 wire...
robb
snipped-for-privacy@aol.com wrote:

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robb snipped-for-privacy@yahoo.com writes:

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 rating.
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)?
scott
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Thank you for the detailed reply, Scott.
Scott Lurndal wrote:

I should also use the bonding screw for the grounding busbar, right?
<snip>

I was planning on burying with PVC type conduit and running #6/3 w/g...assuming I can find that wire. Sounds good?
Robb
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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 DIY'ers.
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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.
Bill Ranck Blacksburg, Va.
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stormy2084 wrote:

You're right, I should go with the bigger stuff. Is wire this large available at the "usual" places?

How do you normally contact the local inspector?
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I bought 01 at Home Depot when replacing my main panel some years ago. I suspect they have everything in between.

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robb snipped-for-privacy@yahoo.com writes:

Your local city/town hall (i.e. town clerk) would know who the inspector is.
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On 19 Apr 2006 13:29:47 -0700, robb snipped-for-privacy@yahoo.com wrote:

If you want copper, go to an electrical supply house for that. The local BORG have sizes for this purpose, but in aluminum.
--
Art


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robb snipped-for-privacy@yahoo.com writes:

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 conductors: - #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 breaker.
Watch your conduit fill percentage. 2" should be more than sufficient as only two of the four conductors in the conduit carry current.
scott
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robb snipped-for-privacy@yahoo.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.
Lew
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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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robb snipped-for-privacy@yahoo.com wrote:

Yes.
No. The 100A rating is a maximum. Nothing wrong with using equipment at less than its rated capacity.

Depends on what breaker you use in the main panel, the type of wire, and how it's installed. For THHN wires in conduit, you can go up to 75A on 6ga copper wire.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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