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#82460 - 11/15/02 02:08 PM 20 cir w/main goes to the Museum
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
I suppose i overwire, having now roughed in a home with 60+ circuits (and counting).
All the dedicated circuits, (or rather , those i have made dedicated) are IMHO, a safety factor, and provide for what wiring of the 50's and 60's do not.

I'd like to hear from the board, i know some of you have been around when the 20 cir w/main was standard fare for the average residence.


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#82461 - 11/15/02 04:25 PM Re: 20 cir w/main goes to the Museum
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
How many sq ft is the house? Does it have AC and other added appliances.

Square D now manufactures a 32 circuit with a 100 amp main to address the problem of enough space for required cicuits. I can't remember the last time that I installed a 100 amp service however.

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#82462 - 11/15/02 04:32 PM Re: 20 cir w/main goes to the Museum
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
spyder,
the house in Q is 5000+ sq ft, no heavy electrical appliances, everythings gas.

& yes, the 30+ ,100a panels are here to stay

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#82463 - 11/15/02 07:13 PM Re: 20 cir w/main goes to the Museum
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
I don't think you are overwiring. Its a big house. The NEC is just the minimum requirements. A good electrician will do more the just the minimums when possible.

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#82464 - 11/15/02 07:41 PM Re: 20 cir w/main goes to the Museum
caselec Offline
Member

Registered: 04/14/02
Posts: 557
Loc: San Jose, CA
Spyder

What is the catalog number for that 32 space 100 amp load center? I don't see it in my Digest.

UL must have changed something since the number of spaces can not exceed 10% of the buss rating. A 100 amp single phase panel can have 10 circuits per buss (100 * 10% = 10), 125 amp 12 circuits per buss (125 * 10% = 12.5), 200 amp panel 20 circuits per buss (200 * 10% = 20) etc. Maybe they are using a 200 amp buss.

When ordering panelboards manufactures can get away with more spaces by using a larger buss even though the label indicates the buss is rated at the size ordered. The company I use to build most of my panelboards uses the same size buss in their 100 - 400 amp panelboards so the number of circuits is unlimited except you can't exceed 42 in on cabinet.

Curt
_________________________
Curt Swartz

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#82465 - 11/15/02 07:52 PM Re: 20 cir w/main goes to the Museum
Fred Offline
Member

Registered: 04/30/01
Posts: 461
Loc: Straughn, IN 47387
The Square D catalog number for a 100A MB 32 space panel is:QO132M100. It's on page 1-5 of the 1997 Digest(my newest edition).
Siemens ITE also makes a 30 space 100A MB loadcenter and has at least since 1996. It's number is:G3030M1100CU.

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#82466 - 11/15/02 08:33 PM Re: 20 cir w/main goes to the Museum
caselec Offline
Member

Registered: 04/14/02
Posts: 557
Loc: San Jose, CA
Thanks Fred. I was looking at the HOMELINE section not the QO. They must be using a 200 amp buss in this panel.

Here in CA we don't use main breaker load centers much and most of the supply houses don't stock many of them. We always install a combination service entrance device and use main lug load center for sub panels. If we do need a main breaker we use a convertible load center or back feed a breaker with a retainer.

Curt

[This message has been edited by caselec (edited 11-17-2002).]
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#82467 - 11/16/02 11:19 PM Re: 20 cir w/main goes to the Museum
Jacuzzi Guy Electric Offline
Member

Registered: 10/25/02
Posts: 33
Loc: Dearborn Heights Michigan Unit...
If you already have the 20 space panel on, then just add a 30 space subpanel MCB, or a 20. And put all your light loads in it. Just to keep the feeder from tripping.

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#82468 - 11/19/02 11:21 AM Re: 20 cir w/main goes to the Museum
Wirenuttt Offline
Member

Registered: 11/10/02
Posts: 267
Loc: Massachusetts
The only 20ckt 100 A mains I've installed lately were replacing old 60 A services for smaller old homes in the city with all gas appliances. There was no need to add bigger than that, half the time after installation there was room for 8-10 more ckts. However I haven't seen a 100 A svc in new homes since the 80s, even then people were trying the 150A service which I'm not sure you can even purchase anyomore. Seems incredibale that you go into a good size home now and see a 40ckt main with a 40ckt sub. Not only that, but the price that's charged for wiring a new home compared to the old 100 A mains has gone up 5 to 10 times. Guess residential aint so bad these days if you can make it work for you.

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