30 amp breaker question

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Old 06-17-15, 11:36 AM
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30 amp breaker question

Thanks for adding me to the forum, this is the first time posting here for me. I am a self employed contractor (retired), and now getting into building Deck Furniture. We just bought a new place and I am working on setting up my wood shop in the existing garage. There are two breakers running to the garage from the main panel box at the house, one 15 amp & one 30 amp. I have done some electrical work in the past (new stuff mostly and terrible at troubleshooting). I have to re-route all the wiring in the garage to fit my needs, and the 30 amp wire was just hanging there (used previously for a rather large air compressor), and my question is: can I hook this up to normal household receptacles, or do I need to install a small junction box and put in a couple 15 amp breakers then go from there with 12/2? I am using only normal everyday power tools (like a compound miter-saw; 20 gallon air compressor; table-saw; planer; etc).
 
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Old 06-17-15, 11:48 AM
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Generally only one feed is allowed per outbuilding, but in some cases multiples are allowed. It sounds like the existing set up for an air compressor was ok because it's a different voltage.

Can you dig a little further and check out how many wires, what size and what color are on the 30A breaker? How do they get to the garage (overhead, underground, conduit)?
 
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Old 06-17-15, 01:38 PM
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Okay, I should have looked at the panel box again before posting.

What I have in the panel box is one double breaker (connected by a bar) that shows 30 on each side, and upon opening it up there is a 10/2 wire fastened into it. The neutral attached to one side & the Black attached to the other.

The other is a single 30 amp breaker w/ a 12/2 wire fastened into it (but seems maybe a little bigger, but definitely not as big as a 10/2), the hot is attached to the breaker and the neutral attached to the the panel box side bar. Both are designated to the garage, and the 30 amp breaker is noted as for the receptacles and lights, while the double breaker is designated for a missing air compressor.

The garage is detached by about 4 feet from the house, and the wires are in a 2 1/2" conduit coming from the house and goes underground, but comes into the garage in a 1 1/2" gray electrical pipe fastened to the interior wall from floor to ceiling, and with what I would say is a single gang sized box attached in the middle with a cover. Upon opening the cover the wires are cut and wire-nutted together matching what is coming from the house. They go up into the attic space (small), and I am sure where the 10/2 goes and ends, but the other is yet a mystery. I am going to have to wait until my son comes this weekend and helps me remove all the junk left behind by the previous owners to see what is going on. By the way the house was built in 95, and the garage ??
 
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Old 06-17-15, 01:49 PM
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Glad you've got the conduit -- that will make this job easier. Neither of the current wires are really well suited to your need, but replacement with something better should be straightforward. Do you intend to use any 240V tools (cabinet saw, compressor, dust collector, welder)? Anything other major electrical intentions we should know about like heat or AC in the garage? I assume this will be a one man shop?
 
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Old 06-17-15, 02:48 PM
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No 240V stuff. My compressor is a typical 20 gallon compressor. I am not going to be in full mass production here, and the deck furniture is just to have something to do while bringing in some cash flow. I may get a window unit AC and a gas heater, or some kind of combo unit, but I have not investigated that yet.
 
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Old 06-17-15, 03:03 PM
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Since the building is detached, you can only have one feed since you do not have multiple voltages like 277/480 and 120/240.

I would with a 120/240 feeder for 50 or 60 amps. The conduit will make this easy and the length will keep the cost down.
 
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Old 06-17-15, 03:35 PM
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No sarcasm intended, but I am not all that concerned about code as far as how many feeds are going to the garage, I mean who's going to check anyway. I don't want to remove and install any wires in the main house panel box going to the garage. Couldn't I remove the double breaker (60 amps it seems) and put in another 30 amp breaker and attach the 10/2 hot to it with the neutral going to the panel bar? This would give me two 30 amp feeds to the garage, and I know that is probably more than I need right now, but who knows what I might end up doing down the road. If I decide to get some equipment that requires more juice its an easy fix. If that is not a problem what would be the suggestion on how to handle the two 30 amp feeds in the garage?
 
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Old 06-17-15, 03:52 PM
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The double breaker you have now, marked with 30 on each part is a 30 amp breaker, not 60. We only give code compliant information out here on the forum. Whether you use the information or not is up to you. Your best bet would be to run #6 wire (4 of them - black, red, white and green) from your panel to the garage through the conduit and pull the other cables/wires out as you won't need them. You could replace the breaker with a larger double breaker, install a subpanel in the garage and distribute your wiring from breakers in it. You would need to ground the subpanel separately to a grounding rod and isolate the ground in the subpanel from the main panel.

It sounds like a bunch of work, but it will create a safe environment for you to work in.
 
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Old 06-17-15, 05:17 PM
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Chandler, understood about the code compliant info you need to stick to. Thanks for the advice everyone!
 
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Old 06-17-15, 05:45 PM
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The other is a single 30 amp breaker w/ a 12/2 wire fastened into it
This would be a code violation. #12 wire is limited to 20 amps max except in special installations, which you do not have.

The issue of having more then one feed to a detached building is a person will shut off one breaker thinking that shuts off the power to the entire garage, as that is what is allowed by code. Then starts to work on things and gets electrocuted.


Couldn't I remove the double breaker (60 amps it seems) and put in another 30 amp breaker and attach the 10/2 hot to it with the neutral going to the panel bar?
Yes, You could change the branch circuit to a feeder using the 30 amp single pole breaker mentioned above and move the white wire to the neutral bar. You then would have a 30 amp, 120 volt circuit. I would suggest then install a small 2-4 circuit sub panel and feed it with the 30 amp circuit. Then install some 20 amp circuits for your tools. You can not use the 30 to feed receptacles as general purpose circuits are limited to 20 amps max. This would be the easiest, least expensive, and code compliant option IMO.

Is it the best path? Well, no because you are fairly limited to what you can do. The others have given info on the best options IMO.
 

Last edited by pcboss; 06-18-15 at 07:10 AM.
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Old 06-17-15, 07:02 PM
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Your best bet would be to run #6 wire (4 of them - black, red, white and green) from your panel to the garage through the conduit and pull the other cables/wires out as you won't need them.
I agree except that I would reduce the green ground to a #10.
 
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Old 06-18-15, 06:36 AM
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We are of course skipping over the most simple option of just replacing the 30A breaker with a 20A breaker and adding a GFCI receptacle on the end. If you find the breaker trips, then worry about upgrading. Until then you've made the current situation safe.
 
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Old 06-18-15, 09:47 AM
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What is the highest I can go on a double poll breaker using the #10 wire?
 
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Old 06-18-15, 10:54 AM
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30A if you put a panel on the other end. The maximum allowed breaker for general purpose receptacles is 20A. The breaker has to be sized for the weakest link in the chain which in this case isn't the wire but the receptacles and tools plugged in which all max out at 20A.
 
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