Sub panel to a sub panel

OOPS!! Yes, I do. Thanks for catching that.

Reply to
Doug Miller
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Code requires the ground and neutral bus bars to be bonded together in the main panel, and requires them to be electrically *isolated* in subpanels.

Reply to
Doug Miller

To be honest I cant rememebr I will have to look if they are isolated in the sub panel. How is the connection between the two "isolated"?

Reply to
stryped

It has been a long time...

Used to be a screw with a paper tag attached to it by the ground and neutral connections. Tag said to install screw to bond ground to neutral or similar words. Leave said screw out if you don't want the two bonded (shrug).

Reply to
Leon Fisk

"Isolated" means not connected electrically. One of the busses will be bolted or screwed directly to the box -- that's the ground bar. The other one will be mounted to the box with plastic insulators -- that's the neutral bar.

In a main panel, the two bars MUST be electrically connected to each other, either by means of a jumper wire or bar connecting them, or by means of a screw driven through the neutral bar and into the box, to provide metal-to-metal contact.

In a subpanel, the two bars MUST NOT be electrically connected.

Thus, if you installed the subpanel "the same as the main panel" then you installed it incorrectly -- and dangerously.

Reply to
Doug Miller

I've seen some panels -- granted, not recently -- that shipped with the bonding screw already installed, with instructions to take it out if the panel would be used as a subpanel.

And the absence of a bonding screw does *not* mean that the two bars are isolated. There might be a bonding *jumper* instead: in a main panel, Code permits bonding the neutral bar to the box directly, or to the ground bar.

Reply to
Doug Miller

If the main panel in the separate garage is within a few feet of the door and is, again, a main panel type with it's own main breaker no other disconnect is required. Running the second sub from the main panel WOULD be the preferred method. Fewer connections between the meter and the load that way. Each series connection is a possible point of resistance, and therefore voltage drop.

Reply to
clare

I don't claim to know the code, but if this is a standalone building, I'd verify the same rule applied. I believe it does but...

Reply to
David Lesher

Pardon? The first sub is protected by the main as well as the 100 amp distribution breaker. Connecting the second sub to that could not contribute to overloading the service. However, it would be better to bypass that second panel and put the outbuilding feed directly on the main breaker panel

Reply to
clare

One of the 100 amp breakers is redundant. Won't hurt anything but not required if the panels are side by side.

Reply to
clare

Any panel in the garage he plans to build is a subpanel, not a main panel. There is a distinct difference between the two.

Reply to
Doug Miller

This applies to any subpanel, regardless of whether it's in a separate building or not. If he installs a separate _service entrance_ in the new building instead -- that is, *not* fed from his existing service -- then it would be a main panel.

Reply to
Doug Miller

Specifically the 100A breaker in the subpanel is redundant. The 100A breaker in the main panel is required, to provide overcurrent protection for the feeder to the subpanel.

In his new building, he needs both: one whichever panel the feeder is taken from (to protect the feeder), and one in the subpanel in the new building (to provide a disconnect for that building).

Reply to
Doug Miller

Doug et al

There is an exception in the NEC for this. If the feed from the main panel is from a 60 AMP or smaller breaker, a main in the sub panel is not required. Also some AHJs have made the exception moot by other requirements. The additional/new panel can be rated at larger then 60 Amps also. Mine is 125 amp. Gives me 20 spaces I think it is. This makes the panel a 60 Amp though. My neutral and ground are separated and I have a 10" ground bar also. Habitable structure or not, also makes a difference.

Bob AZ

Reply to
Bob AZ

I think you miss read me. The first sub is protected by a 100, I was say don't bypass the 200 amp main in the main panel, or come off the meter can. The service entrance is should only be wired for 200 amp, and feeding a 200 amp panel and a 100 panel off the meter could result in drawing 300 amps through the service.

Reply to
Tim

-is 200 amps, and my current sub panel is 100 amps?) Can I put another

-100 amp panel in my new garage/shop?

Yes. Just remember if your collective load cannot exceed 200 amps. That's why you want all your loads to come through the original main breaker.

-l have to route the cable under the house (crawl space) and

-outside under a deck to a ditch to the new shop. So you are sayign a

-disconnect where the wite comes out of the house? (Which would be

-under the deck).

Probably not, but I don't recall what the codes say.

-B the way, I will have to disconnect somethignin the main panel to

-give me space for the extra sub panel. If there is not enough slack to

-move it over. (wire wise). What can I do?

Splice it.

Reply to
Tim

Having another Main Breaker disconnect in the subpanel in the detached building isn't an absolute necessity if you have six or less circuits in the sub-panel (Per 2002 NEC Article 225.32 and the exceptions see "Installations under single management", and Article

225.33)

But it is still a darned good idea to have another Main - so you can Kill It all RIGHT NOW. Cheap insurance, but it does make another point to find and reset if you get a nuisance trip...

You have to keep the Neutral and Safety Ground totally seperate except at the Main Service Panel - meaning you need to run four wires out to the detached shop. Two hots, Neutral and Ground.

Meaning if it's an aerial run you have to buy Quadplex aerial service wire to get three insulated plus a bare messenger for the ground. Triplex like Edison uses won't cut it.

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Reply to
Bruce L. Bergman

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