Rewiring old garage

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Old 02-14-10, 08:45 PM
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Question Rewiring old garage

A few weeks ago I started what I thought would be a simple job in Bothell, WA.

I was just going to rewire my garage but a friend convinced me it was worth the trouble to get the permit and have the job inspected. With permit in hand this is what's happened so far.

I thought the garage had two circuits each with a 15amp breaker. One breaker controlled the wall receptacles and over head lights, the other only controlled the outdoor light on the front steps for our sidewalk.

The reality was there are two wires, each is 12-3 romex, but one wire is totally dead and the other 12-3 wire has a breaker for the garage/receptacles/lights, and the one for the front light, sharing a common ground.

I wanted to have 7 receptacles and the front light on one circuit, and 4 overhead lights inside plus 4 outside (yard) lights on the other. From what I could find online this seemed to be an acceptable load for each breaker, which would be to code anywhere.

I think this would still work using the black and red as separate hot wires for each circuit and the white as a common ground except now I'm finding that the wall receptacles have to be GFCI. If so, this won't work with a single 12-3 wire, I'd have to have 2 12-2 wires.

If this is true we're talking ripping siding off to run another wire unless maybe I get lucky and can find the other end of the dead wire loose and ready to hook up to the breaker box.

So, sorry for the dissertation. I guess the question is can I still have two circuits on a single romex 12-3 or does the GFCI requirement apply to rewiring existing garages (built in the 1970s) that weren't wired with that requirement in mind?

Thanks.
 
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Old 02-14-10, 08:53 PM
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If you are rewiring and have a permit, you must meet today's code (what ever that is in your area). Use GFI receptacles and it should work. By the way, the white wire IS NOT a ground, it's the neutral. You still need to have a ground in addition to the white neutral.
 
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Old 02-14-10, 09:24 PM
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The reality was there are two wires, each is 12-3 romex,
Just so we are clear on terms those are not wires. They are cables. The individual conductors in them are wires. A detached garage can only have one circuit with the exception of an outside light. Is this a detached garage?

Your best bet is probably going to be to run new wiring to the garage. If you have no ground wire the cable that is there can not by code be extended. First though let us know what loads the garage will have such a table saws, air compressors, welders, electric heat etc. Once we know if it is a detached garage and expected loads we can go from there.
 
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Old 02-14-10, 09:37 PM
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Thumbs up Terminology

My apologies for my lack of knowledge about terminology. Obviously I don't do this for a living.

Each 12-3 cable has 4 wires. A black, a red, a white and a bare copper. Once I found the red wire I had to go research what it was and now understand it's a hot wire, as opposed to a neutral, and I knew the bare copper is a true ground.

The garage is semi-detached, it only connects to the house at one corner, no common walls.

I do intend to have a shop out there, but no heavy duty appliances. No heating for sure.

I'm still hoping this can work without having to run another cable. Or, that the dead cable can be engergized with little effort.

Why would someone run a dead cable anywhere? Maybe giving the option for future 240v usage?
 

Last edited by kadini; 02-14-10 at 09:41 PM. Reason: typos
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Old 02-14-10, 09:45 PM
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Originally Posted by ray2047 View Post
Just so we are clear on terms those are not wires. They are cables. The individual conductors in them are wires. A detached garage can only have one circuit with the exception of an outside light. Is this a detached garage?

Your best bet is probably going to be to run new wiring to the garage. If you have no ground wire the cable that is there can not by code be extended. First though let us know what loads the garage will have such a table saws, air compressors, welders, electric heat etc. Once we know if it is a detached garage and expected loads we can go from there.
cant he use a 2 pole breaker and make a MWBC protecting both with a gcif
 
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Old 02-14-10, 09:48 PM
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Originally Posted by kadini View Post
Why would someone run a dead cable anywhere? Maybe giving the option for future 240v usage?
its slightly possible it could be running to a switch box in the house to control a light from insideBeer 4U2
 
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Old 02-14-10, 09:56 PM
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Arrow Mickey Mouse Solution

I still hope to have two circuits and all the lights wired in the walls and actuated with switches.

But, I could just use the Black & White wires, not hook up the Red (no second circuit) and just have the GFI wall receptacles on that one circuit.

Then my internal and external lighting could all be done using extension chords that plug into the receptacles.

This would meet the intent and letter of all codes, right? Last resort, preferable to ripping out walls to run more bundles.

Braether, to be honest I didn't understand what you said, but it sounded like you thought I could make it work with one 12-3 bundle and two circuits?
 
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Old 02-14-10, 10:54 PM
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Maybe there isn't a problem

I found a thread on one forum that said you couldn't use GFI on a 12-3 romex cable, i.e. the GFI couldn't share a common neutral.

This was the reason for my initial query here.

But I just found another post on another forum that said the GFI will work on a common neutral, you just have to have a GFI receptacle on each circuit after the split.

Is that true? Is this what Braether3 was talking about?

If so would I still need the 2 pole breaker? And, since once circuit would only be for lighting would I need GFI on it at all?

Thanks for all the help!
 
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Old 02-15-10, 09:12 AM
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cant he use a 2 pole breaker and make a MWBC protecting both with a gcif
Yes. He would install a disconnect at the garage and run two separate 12-2 cables after the disconnect. He could either use a 240v GFCI breaker, maybe expensive, or a non-GFCI breaker and use a GFCI receptacl (cheaper) as the first outlet after the disconnect on each 12-2 cable. The disconnect can be a simple DPST switch rated at 20A or greater.
 
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Old 02-15-10, 09:34 AM
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I'm going to pretty much reiterate what others have posted.

With the new work you will have to update it to current code in your area.

You can have your two circuits you want in your garage using the single 12/3 cable. This is OK under the Code as only one feed. This will be a mulitwire branch circuit (MWBC) and will need to be protected at the house panel by 2 pole, 20 amp breaker or less.

A disconnect will be required in the detached garage. As others have posted this can be a simple as a two pole, 20 amp switch.

All receptacles are required to be GFCI protected. This would be done in the first receptacle box with the feed going to the LINE and the cable going to the other receptacles on the LOAD or the GFCI receptacles.

When branching off the other circuit ( say red) do not connect the neutral to the LOAD side of the GFCI. Just pigtail the neutral to the GFCI. The red you will splice through.
 
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Old 02-15-10, 11:39 AM
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Originally Posted by kadini View Post
But I just found another post on another forum that said the GFI will work on a common neutral, you just have to have a GFI receptacle on each circuit after the split.
Yes that's correct. A GFCI cannot use a shared neutral for downstream (LOAD) protection. However if you split the multiwire circuit into two legs using 12/2g cable a single GFCI device can protect each leg.

Another option is to use a two-pole GFCI breaker on the circuit which will protect everything on each leg, regardless of the splits and forks. This option is more straightforward, but usually more expensive as the double-pole GFCI ranges from about $60-200 depending on the brand of your panel.

Your final option is to use a GFCI receptacle at every location and only connect the LINE terminals. This is effective, but can also get pricey if you have a lot of receptacles as GFCI receptacles are roughly $10/ea.

If so would I still need the 2 pole breaker? And, since once circuit would only be for lighting would I need GFI on it at all?
A multiwire branch circuit requires a double-pole breaker, but it does not have to be a GFCI breaker if you go with one of the other options above using GFCI receptacles. GFCI is required on your lighting circuit only if the lights plug in to receptacles; if they are hardwired no GFCI is required.

Why would someone run a dead cable anywhere? Maybe giving the option for future 240v usage?
Guesses:

1) Perhaps the cable is damaged and someone abandoned it when the new one was run.

2) Future use for 240V.

3) Three-way switch traveler to control garage lights. Maybe you also have a mystery switch somewhere in the house?
 
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Old 02-15-10, 07:23 PM
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Lightbulb Thanks for the help and a couple of questions

First off, thanks to everybody for the help!

I need a 2 pole 20 amp breaker to replace the two single breakers (right next to each other in the box), so if one circuit trips the other goes too. Need to make sure I know how to de-energize the breaker box for that task. Or should I hire somebody to do that? As long as I'm sure the power's off I'm willing to try anything.

Then I need a light switch in the garage through which all the garage power is routed that serves as a disconnect? Not a problem, just want to make sure I understand that part.

I have already successfully installed GFI receptacles in other projects so I think I can handle that part.

Thanks again for all the help!
 

Last edited by kadini; 02-15-10 at 07:25 PM. Reason: typos
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Old 02-15-10, 08:48 PM
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gotta be a commercial type 20 amp 2 pole single throw light switch be careful not to buy a 4 way lightswitch
 
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Old 02-15-10, 08:54 PM
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You should be able to safely change the breakers with the main breaker off but be careful because there are still live parts in the box even with the main breaker off. If you are uncomfortable though working in the panel get an electrician.
 
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Old 02-15-10, 09:37 PM
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Originally Posted by braether3 View Post
gotta be a commercial type 20 amp 2 pole single throw light switch be careful not to buy a 4 way lightswitch
A 30 ampere air conditioning disconnect would do as well and might be cheaper. Bonus is that it has its own enclosure.
 
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Old 02-15-10, 09:55 PM
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Lightbulb Thanks again

For all the help.

This is a great forum.
 
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