Subpanel for garage(s) Options/Opinions?

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  #1  
Old 02-17-14, 05:18 AM
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Subpanel for garage(s) Options/Opinions?

My main service panel (150amp) is getting full, and I have about two spots left.
I need to get 220 into the integral garage for my air compressor.

I initially was just going to use those last two spots and run a dedicated line for the compressor then I got to thinking... (That's where I'm dangerous )

I'm eventually planning on building a detached garage this year or next.

Would I be better off running say 6/3 off a 50amp breaker in the main to feed a sub in the garage?

I can then feed my compressor from it, and eventually run another 6/3 off of it to feed the detached garage.

Is that a good future proof design? I don't see myself running high amperage loads in both garages at the same time so I'm pretty comfortable with 50amps between the two.

But can I legally feed a sub panel in a detached garage like that?
 
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Old 02-17-14, 05:36 AM
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Copper 6/3 with ground to feed panel.

- removed 60 amp as pointed out is for disconnect means at separate structure.
 

Last edited by Astuff; 02-17-14 at 06:39 AM.
  #3  
Old 02-17-14, 06:03 AM
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The disconnect needs to be rated 60 amps, not the feeder. From Article 225.39

(D) All Others. For all other installations, the feeder or
branch-circuit disconnecting means shall have a rating of
not less than 60 amperes.
 

Last edited by pcboss; 02-17-14 at 06:42 AM. Reason: added code cite
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Old 02-17-14, 06:27 AM
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From what I've read I could upsize the 50 to a 60 with 6/3 but I'm a little concerned doing that with the distance.

The first sub would be about 40 feet from the main, then another 60-70 beyond that to the detached garage.

I figured down sizing the breaker feeding the detached garage to make up for the distance. 4/3 is probably not going to be cost efficient nor easy to work with.


It might make more sense to feed two separate circuits to the detached garage than to install a full sub panel.
 
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Old 02-17-14, 06:43 AM
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I don't understand why you want to downsize based on the distance.
 
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Old 02-17-14, 07:59 AM
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I always thought that over a certain distance you needed to upsize the wire, or downsize the breaker.. (I've been wrong before, that's why I ask )
 
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Old 02-17-14, 08:08 AM
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The wire may need to be up sized based on distance and load. The breaker does not need to be downsized.
 
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Old 02-17-14, 08:10 AM
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I always thought that over a certain distance you needed to upsize the wire, or downsize the breaker.. (I've been wrong before, that's why I ask )
Voltage drop is rarely an issue in residential wiring. Now, if the future garage were to be 150 feet away, it might become an issue with heavy loads out there.
 
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Old 02-17-14, 08:15 AM
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Sorry I was editing that post as you were replying..

So all that said I can technically put a subpanel in the attached garage and feed it with a 60a breaker and 6/3 and get my 220 circuit that I need out of it now.

Then when the time comes and I build the outside garage, I can still put a 60 amp breaker in to feed the outside garage as long as I have a 60amp disconnect out there?
 
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Old 02-17-14, 08:34 AM
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The disconnect needs to be rated 60 amps, not the feeder. From Article 225.39

(D) All Others. For all other installations, the feeder or
branch-circuit disconnecting means shall have a rating of
not less than 60 amperes.
The most common or typical way of providing the disconnect at the outbuilding is by installing a 2 pole backfed circuit breaker and then installing a main breaker hold-down kit. Look at the picture of this Cutler-Hammer 60 amp 2 pole breaker.

Eaton 60 Amp 2 in. Double-Pole Type BR Replacement Circuit Breaker-BR260 at The Home Depot

Now, run your cursor over the picture and you'll get a closer view. If you look closely you'll see two important things. 1.) This page is for a 60 amp breaker, but the picture is of a 100 amp breaker. This isn't a big deal because the picture is just for illustration purposes. 2.) Look at the hole between the two poles - It's next to the UL mark on the breaker label. That hole is for the long screw in the main breaker hold-down kit.

The point is this; 2 pole breakers of lower amperage than 60 amps (15 amps - 50 amps) do not have the hole for the hold-down kit. Therefore, the 60 amp 2 pole breaker is the smallest breaker that can be used as a backfed main breaker/disconnect in an outbuilding.
 
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Old 02-17-14, 09:18 AM
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Or you can provide the disconnect with a main breaker panel. Sometimes common main breaker panels that include the main breaker and several branch circuit breakers ate cheaper then main lug only panels with no breakers included. The main breaker is used only as a switch so it can exceed the size of the supplying breaker. No supplementary hold down is required for a main breaker. Boxes within the same structure as the first OCPD do not require a disconnect.
 
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Old 02-17-14, 09:20 AM
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One caveat, the lugs on the main breaker may not be listed for use with smaller conductors. A splice could be made.
 
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Old 02-18-14, 02:16 PM
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Thank you all for the information, I picked up my subpanel today. Now to go spend a small fortune on wire!

One more quick question, the subpanel I picked up only has a single non bonded bar. Should I put all my grounds and neutrals under it, or should I install the separate bar for the grounds?
 
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Old 02-18-14, 02:26 PM
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Should I put all my grounds and neutrals under it, or should I install the separate bar for the grounds
Code states all subpanels must have a bonded ground bar and all grounds will be connected only to that bar.
 
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Old 02-18-14, 04:36 PM
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In addition to the ground bar you will need to a grounding electrode like a rod or rods.
 
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Old 02-23-14, 05:05 AM
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Just finished this up yesterday. I'm fairly pleased how it turned out..


As I was finishing up and installing the new breaking in my main panel I heard a hissing sizzling sound from the other room. Next project, water heater!

In addition to the ground bar you will need to a grounding electrode like a rod or rods.
This is just for the detached garage subpanel, right?
 
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