Subpanel question

[nate379]

Does a subpanel that isn't close to the main have to have a main breaker?

Reason I ask is a subpanel without main lug is $28 and one with main is $75.

Panel will be fed 30amp 240v line from garage about 100ft and will power an air compressor and few lights/outlets.

 

[Charles (in GA)]

Detached structure? The detached structure must have a disconnect at the structure, whether you do that with some sort of outside disconnect where the power enters, or at the sub panel inside the detached structure is your choice, but yes, since its detached, it has to have a disconnect. also, the disconnect must be rated at a minimum of 60 amps. NEC 225.39

The circuit breaker in the main panel supplying this feeder circuit can be less than 60 amps, just that the disconnect (a switch is OK, not necessarily a circuit breaker) has to have a 60 amp or higher rating.

Charles

 

[chevotass]

x2 on what charles said.

 

[sberry]

in the same structure it doesn't need a main. Also if you use a 6 space panel it doesn't need a main, even service entrance can be fed main lug.

 

[Charles (in GA)]

in the same structure it doesn't need a main. Also if you use a 6 space panel it doesn't need a main, even service entrance can be fed main lug.

Forgot to mention that, the six handle rule. If you don't have over six handles to operate to kill all power, then no disconnect is needed.

Charles

 

[nate379]

Yes detached structure, about 100ft from main panel.

I will have 3 circuits on the panel.
A 15a 240v for the compressor, a 15a 120v for lights and a 15amp 120v for outlets.

The panel I looked at using is something like this:
http://www.google.com/products/cata...og_result&ct=result&resnum=4&ved=0CCwQ8wIwAw#

 

[sberry]

One of the code guru;s can correct this if its wrong, you might be able to use that if one or 2 of the breakers is 240 due to the 6 handle rule, you could always back feed a breaker to install a main but the 6 space panels found in box stores for about the same price definitely meed the intent. Personally due to the cost of wire etc I might consider number 2 alum which is what I use for separate building feeds, good for 90A, very little V drop and leaves room, would run a 50A welder if the need should ever arise and the cost is nearly the same as a 30A copper wire. They make a quad assembly just for this common application.

 

[sberry]

Lowes and Home Depot both had the wire, HD was cheaper and had full size neutral.

 

[nate379]

The wire was put in the ground almost 2 years ago and has been hooked up at the garage side already. I was just waiting to have 4 walls and a roof to wire the shed which I am near that point now.

The building is just a storage shed, the main reason for running juice was for the compressor, but I figured that a few lights and outlets would be handy. I don't plan on doing any work out there, but if I needed to plug in a battery charger, trouble light or maybe a deep freeze freezer type thing.

I might just backfeed a breaker on that $30 panel.

What is the deal with this 60 amp "rule". If I have a panel that is ok for 100 amps, but I have a 30 amp breaker on the main to feed and then put a 30 amp breaker on the sub as a main breaker, is that following that rule?

 

[Aceman]

Price out a 100 amp main breaker panel first. I used to backfeed breakers all the time for small subpanels, but I've been getting pretty good prices on main breaker panels lately, so I've been using those.

You can lose up to 4 spaces total when backfeeding a breaker in some panels, that's a lot of real estate in an 8 space can.

 

[nate379]

$75 for a 100 amp with main, $30 for 100 amp without. Smallest panels sold at Lowes in the Siemens line.

I'll have to check on backfed main taking up spots. With main I would need 6 spots.

 

[Norcal]

A backfed plug-in circuit breaker is required to have a hold down clip / retainer on it.

 

[Charles (in GA)]

What is the deal with this 60 amp "rule". If I have a panel that is ok for 100 amps, but I have a 30 amp breaker on the main to feed and then put a 30 amp breaker on the sub as a main breaker, is that following that rule?

No, it is not, if you are depending on that for the service disconnect at the subpanel. Should you exceed 6 handles at the subpanel, the "main" would need to be at least 60 amps to meet the rule.

You could put a 60 amp rated A/C disconnect on the outside of the building or a weatherproof handle operated 60 amp rated switch on the outside (or inside) and meet the rule.

Charles

 

[nate379]

I did a bunch of reading and nothing I could find says anything about the wiring to the building needed to be 60 amp or the feed breaker even.

This thread is a good read since it's about the same as what I am doing:
http://www.selfhelpforums.com/showthread.php?t=18557

From what I can gather, a guy can run a 30 amp feed, but at the subpanel it can be whatever, as long as it's 60amp or greater. It's not logical to me, but I don't make the rules.

If I get a main lug load center, am I able to backfeed a 60 amp breaker?

Or so I have to get a main breaker load center, like this one? http://www.lowes.com/pd_94657-1318-...currentURL=/pl__0__s?Ntt=siemens+main+breaker

 

[Charles (in GA)]

I did a bunch of reading and nothing I could find says anything about the wiring to the building needed to be 60 amp or the feed breaker even.

That is correct

From what I can gather, a guy can run a 30 amp feed, but at the subpanel it can be whatever, as long as it's 60amp or greater. It's not logical to me, but I don't make the rules.

It can be a disconnect on the outside of the building (some local codes require it on the outside) and doesn't have to be a breaker, just a rated (as service equipment and at 60 amp or more) switch. --OR-- You limit the installation to six handles or less, but the moment you exceed six handles, back you go to installing a "main".

If I get a main lug load center, am I able to backfeed a 60 amp breaker?

Certainly. Be sure and get the retaining kit for the breaker. It should be listed on the inside of the panel door, decal, or instructions. Required for a backfed main.

Or so I have to get a main breaker load center, like this one? http://www.lowes.com/pd_94657-1318-...currentURL=/pl__0__s?Ntt=siemens+main+breaker

Your choice.

There is one exception to this whole mess, and that is 225.36 (exception) that says that for residential outbuildings and garages, a "snap switch" or three or four way switches are allowed as a disconnect means, however, this would be in an installation where there is no subpanel and you are running a single circuit (which is a branch circuit) from the house to the garage or outbuilding, and not distributing it within the building (making it a feeder circuit).

Why don't you get the main lug panel, and go out and spend $15 on a 60 amp rated outdoor box type A/C disconnect, mount it on the outside of the building and you are done. It is prob a lot cheaper than the main breaker or even the backfed breaker method. You don't need a breaker, just a switch or disconnect. It does have to specify that it is rated as "Service Equipment" however, on the decal in it.

Charles

 

[Norcal]

Why don't you get the main lug panel, and go out and spend $15 on a 60 amp rated outdoor box type A/C disconnect, mount it on the outside of the building and you are done. It is prob a lot cheaper than the main breaker or even the backfed breaker method. You don't need a breaker, just a switch or disconnect. It does have to specify that it is rated as "Service Equipment" however, on the decal in it.

Charles

The pull-out A/C discos are intended for 240V loads only as no provisions for a neutral are made in them. (Only 2 lug positions provided, so no spot for grounding electrode conductor & any mods would violate the listing).