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.
Cite, please? I thought that was for service entrances, not subpanels.
Hmmm. From my copy of the NEC 2002 Handbook:
230.71(A) "The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception Nos. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers ... " 408.16(A) "Each lighting and applicance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.""Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard."
Seems you're correct, Doug.
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
...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!"
TRUE.
Known in some circles as the "6 hand" rule.
Regardless of whether a panel is a "sub" or a "main", you must be able to disconnect ALL power distributed by that panel in a maximum of 6 motions of the hand.
I seen some very clever schemes used by some contractors in an attempt to avoid a main C/B, but most don't get approved.
Lew
Coleman 10HP, Contractor type, 5,000 Watt engine-generator located Long Beach.
120/240V outputBoat yard has power so have no further use for it so it's for sale.
Will make a good back up power supply.
SoCal area only.
If interested, contact off list.
Lew
FALSE!
I -wanted- a master-cut-off in the main breaker panel in my condo when I was rebuilding the kitchen, and replacing the breaker panel. (went from 14 to 20 circuits, original panel mfr long out of business, had to enclosure, et al.)
City inspector would not allow a 100A breaker at panel feed, because there was 100A breaker (only) panel in utility entry room.
I had, per inspector, choice of: 1) run with *no* 'master-cut-off breaker' in unit. 2) try to find something like a 95A breaker to use as the 'main' in unit. 3) replace (obsolete, mfr out-of-business) breaker at utility entry room with something like 110A,, and use 100A in unit.
"1" was the only 'financially viable' alternative.
I'm not sure I understand your explanation; however, the "6 hand rule" applies if you are going to comply with NEC.
Got any idea what this "inspector" had for a day job?
Lew
Doing electrical rework, _with_ a city permit, it was specified _by_the_ city_ that I was to use a sub-panel (24 circuit capacity) *WITHOUT* a main breaker in it. Because the main breaker was in the panel in the building utility room.
I _wanted_ a master-cut-off in the sub-panel, but there was no =feasible= way to do it *and* be code compliant. Since it was _not_ required by code, I ended up going without it.
Note: *NONE* of the 30-plus units in my condo building has a master- cut-off in the 'in unit' sub-panel. All have at least 14 circuits, and it is comparatively 'modern' construction -- circa 35 years old.
"Cite please". It was established in another sub-thread that that 6-breaker max w/o a main cut-off applied to a 'service entrance' panel only. They even quoted the relevant NEC section. Now, the question is, can you back up -your- claim.`
Note: the person posting the NEC section showing 'service entrance' only was someone who had made the same assentation you did, and was admitting he had been wrong.
Yeah, he was the CHIEF ELECTRICAL INSPECTOR for the city, and department head. 25+ years on the job.
He was a 'good guy' -- out of six 'somewhat unconventional' things I wanted to do, he found code interpretations (and provided 'chapter and verse' just- ifications) that let me DO five of them. (Just one of which saved me the cost of at least 2 electricians for a full day, and, incidentally, around $200 in parts.) It was only the master-cut-off that didn't fly. to be 'code compliant', I could go _without_ a master-cut-off in the sub-panel, or I could use one that had to be _smaller_ than the main breaker downstairs. (this required either a 'nonstandard' capacity breaker upstairs, or replacing the one downstairs with a bigger standard value. Neither of those options was financially viable, albeit for different reasons.)
To this day, I don't understand the 'smaller breaker' requirement. If I've got a 100A breaker on each end of a 100+A-capable wire, "at least" one will trip on an overload. There's no safety issue. The inspector agreed with my logic, but said that, nonetheless, the code didn't allow it. So, I went the 'code compliant' -- no main breaker in the sub-panel way. 22 circuits.
No longer have access to a current code book.
My comment was based on being bloodied from having to work with local inspectors and contractors as a distribution equipment supplier for about 15 years.
Your description of your experience is certainly strange.
Just curious, was the main C/B visible from the distribution pnl in question?
Lew
Well, if you could see out the door or the condo, across the hall, down three flights of stairs, through the laundry room and into the utility room, then yeah, you could claim it was visible. Now, I was straight across the hall from the stairwell, the folks at the far end of the floor had a somewhat more obscured line of sight.
I suspect he is being impacted by local rules. I have used main breaker panels as sub panels when they are located a long ways from the main. I don't usually as cost of a 3 phase 208 volt 200 amp breaker adds quite an expense. Also since we usually have to protect according to available fault current fuses get a lot more practicle. I don't think NEC prohibits it. Feeders have to be protected where they are powered from unless using the tap rules. Mike M
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.
There was hardly anything in the municipal code that modified in any way the National code.
There was an addition that _any_ new (addition or replacement) panel had to be inspected by the city, and something else equally earth-shaking. :)
Yup. And there is apparently a requirement that _if_ there is a breaker at the 'downstream' End of the feeder, it must be smaller than the one at the 'powered from' end. which meant if I wanted to use a 100A 2-pole in the in-unit panel, I had to have 'something bigger' at the feed end. But, the building was built (1960s) using "Federal" breakers/panels, etc. finding 'standard' replacements is an exercise in futility -- let alone trying to find, say, a 125A one. the other option was to put something 'a little smaller' than 100A in the in-unit panel. It's amazing how scarce 'residential style' breakers are with ratings above 60A, and below 100A. and how _expensive_ something like a 95A breaker of that ilk is.
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
Ah well, I rarely argue with inspectors. Except when they're out-and-out wrong, and I can prove it, that is. At another place, I crossed swords with a City of Chicago electrical inspector -- over the City of Chicago Electrical code. (The Chicago Code is _not_ based on the NEC, in fact it predates it. It is much stricter than the NEC about some things, and more lax about others. It is also written such that it is _very_ difficult to figure out exactly what is, or is -not-, allowed in any given situation. Methinks that this is deliberate, to enhance inspector revenues.)
Anyway, this inspector didn't like the way something had been done. And cited the code section that it was in violation of. And I cited the section that said _his_ section "didn't apply" if conditions X, Y and Z were met, and that =this= installation have conditions X, Y, and Z. He countered with a section that said condition Y had this other requirement under "these" circumstances, and that we did fall under that. Whereupon I pointed out that section thus-and-such said his section applied only when condition W existed, which did not exist here. This went on for a while, but eventually he "went away mad" -- *without* writing a violation,
*or* getting a bribe. He was _not_ a happy camper. :)The next week the fire inspectors came calling. *sigh*
They were thorough, but didn't find anything that they could write a violation for, either.
Also when you are serving a second building on the same service.
225.33Mike 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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