yet another subpanel question

Greetings All!

I am in the process of wiring up a shed in the backyard for use as a workshop. 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. Should I just buy a ground bar and install it in the panel and connect it to a new grounding rod? 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? The subpanel does not have a main breaker in it. 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?

Thanks, Robb

Reply to
robb_jr
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Check here for guidance on the grounding:

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recently called my local building inspector and found him to be very helpful and forthcoming without ever asking for my address.

Reply to
RayV

I'll defer to others on this one. The conduit should serve as a ground, but some placed might require a separate ground wire.

I did exactly this. It's not a problem since the breaker protects the wire.

Size it to match the breaker you put in the main panel. You'll need something like #8 or #6 for 60 amps. I can't remember what I used. It will be disasterous if you size it too small.

brian

Reply to
brianlanning

Yes and do not install the jumper/green screw that would bond the neutral bar. Run a 4 wire feeder.

That is OK if you have less than 6 breakers in the sub.

4 ga copper is a good choice. That gets you up to 85a The ground wire can be #8 copper up to 100a
Reply to
gfretwell

Should have said 6 or less

Reply to
gfretwell

How does the number of breakers in the subpanel matter?

brian

Reply to
brianlanning

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

Reply to
Scott Lurndal

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:

Reply to
robb_jr

NEC requires a main for more than 6 breakers.

Reply to
Art Greenberg

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!"

Reply to
Unquestionably Confused

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

I was planning on burying with PVC type conduit and running #6/3 w/g...assuming I can find that wire. Sounds good?

Robb

Reply to
robb_jr

Buy a separate ground bar kit from a SQ D distributor and install it.

No. Just install a 2P-60 as a main C/B the in the sub panel.

Bigger is better.

I'd run #2 but #4 will do the job.

Lew

Reply to
Lew Hodgett

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.

Reply to
stormy2084

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.

Reply to
Gooey TARBALLS

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.

Reply to
ranck

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?

Reply to
robb_jr

Reply to
Gooey TARBALLS

Your local city/town hall (i.e. town clerk) would know who the inspector is.

Reply to
DJ Delorie

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

Reply to
Art Greenberg

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 . . . .

"Lew Hodgett" wrote in message news:aew1g.126$ snipped-for-privacy@newsread4.news.pas.earthlink.net...

Reply to
Steve DeMars

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