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Willski
08-27-2008, 12:24 PM
I am running new service to my detached garage. Any thoughts on sizing.

I've talked to an electrician that said if you really don't want to box yourself in later, run a 55 amp breaker and #6 wire. Seems like a lot, but would allow for future changes easier than undersizing it.

Jimmauburn
08-27-2008, 12:33 PM
Sounds about right to me ?? I wouldn't really run anything smaller that way you can have a little extra for add ons at a later time ??

flipper
08-27-2008, 12:39 PM
I'd go bigger if you do any welding. I just put a sub panel in my garage, and went with 75 amp breaker service. I run a 220 welder, 220 air compressor, and a 110 welder off it though.

JimN
08-27-2008, 12:50 PM
Distance and load are everything. Also, you'll have to bond the garage's panel to the house's service panel and install ground rods, per code. Go big, or go home. You'll spend far more in a service upgrade if you undersize it now than the difference will be if you use smaller cable.

If they're going to be trenching anyway, run a second conduit for low voltage wiring. That way, you can have network/phone/coax/audio zone/security cameras in the garage without trying to do it wirelessly.

Jimmauburn
08-27-2008, 12:51 PM
Well Flipper has a point there ?? Got any major 220 ambitions or planning on installing any air conditioning out there in the future ?? May even consider a 100 amp if you have many 220 components to add later or if there may be that air conditioner (220)?? If all you have are some 110 outlets and light circuits the 55 amp should be just fine.

mayo93prostar
08-27-2008, 01:23 PM
sounds good but to determine if it is adequate, you need to list things you want to power and add them up based on what do you expect to be operating at the same time, with a little margin left over. caution that air compressor could kick on at anytime but you are not likely to be running two welders, grinder, etc. all at the same time. you only have two hands. but how many friends do you have that may be helping. count lights, fans, battery charger, heater, leaf blower (clean floor), shop vac, air compressor, table saw, etc.

flipper
08-27-2008, 01:27 PM
Well Flipper has a point there ?? Got any major 220 ambitions or planning on installing any air conditioning out there in the future ?? May even consider a 100 amp if you have many 220 components to add later or if there may be that air conditioner (220)?? If all you have are some 110 outlets and light circuits the 55 amp should be just fine.

Even if you don't need 220 right now, I'd still set the service up for it. Get it all done now, so you can add an outlet or what ever later. If you decide to add anything, it will be easy. :twocents:

flipper
08-27-2008, 01:29 PM
Oh, also be careful not to exceed the house panel though. I had to up my service to the house to do all this.

Willski
08-27-2008, 01:44 PM
The garage is mainly a storage area. 2 stall. With the boat in there, I won't be doing too much heavy work. My only concern with load might be if I install a small electric heater that hangs from the ceiling. So can I run a 220 outlet if I use the #6 / 3 wire with ground?

flipper
08-27-2008, 01:54 PM
It will depend on the heater, and the distance. You are doing a sub panel right?

Roonie's
08-27-2008, 02:26 PM
Go big for sure..... I had the same issue with a pole barn I put up and decided to go big to accomadate future welding/airconditioning/heater. I don't have those things now but if I ever add those things I have it already there. I would have to learn to weld first (details). The point is you may use the space for something completely differeent then what you have envisioned for it now. I also ran cable, and cat 5 out there too for future.

stuartmcnair
08-27-2008, 02:55 PM
Distance and load are everything. Also, you'll have to bond the garage's panel to the house's service panel and install ground rods, per code. Go big, or go home. You'll spend far more in a service upgrade if you undersize it now than the difference will be if you use smaller cable.

If they're going to be trenching anyway, run a second conduit for low voltage wiring. That way, you can have network/phone/coax/audio zone/security cameras in the garage without trying to do it wirelessly.

I second that. Run both in conduit. I personally would run it in two inch pipe. That will make any pulls easy.

Willski
08-27-2008, 04:45 PM
It will depend on the heater, and the distance. You are doing a sub panel right?

Yes. i will do a sub-panel in the garage.

flipper
08-27-2008, 04:49 PM
You will pretty much have to run 220 out there to the panel I think. So, it will be in the panel, just make the wire getting there big enough to run everything, and then some. How far will the wire be ran?

flipper
08-27-2008, 04:52 PM
Play with this....it should help you some. You'll also want to know what the service to the house is. If you have 100amp service, and the panel already has 90amps worth of breakers in it, you need to up your service to do it right.



http://www.csgnetwork.com/wiresizecalc.html

Willski
08-27-2008, 05:05 PM
The actual run from the main to the sub-panel in the garage will be about 50 ft.

flipper
08-27-2008, 05:12 PM
Then #6 wire should do everything you want it to. I was thinking it would be further than 50ft. Do you know how much room you have in the box in the house amp wise?

Willski
08-27-2008, 05:27 PM
I haven't really looked that closely yet. I kind of assumed that since I had 200 amp service I would be fine, but this is assumption. I have a 1400 sq. ft. house with nothing extravagant, so I should be okay.

M-Funf
08-27-2008, 05:49 PM
The actual run from the main to the sub-panel in the garage will be about 50 ft.

Aerial or underground? I've got some great wiring diagrams for separate buildings. Here's an example:

39573

Willski
08-27-2008, 06:09 PM
Aerial or underground? I've got some great wiring diagrams for separate buildings. Here's an example:

39573

underground

M-Funf
08-27-2008, 06:14 PM
Then you probably need this diagram. It appears that you can either run a ground between the two, or you can ground at the other end. If you ground at the other end, you save one 50' conductor. Make sure to size your conduit for the number and gauge of wires you're running.

39574

39575

JimN
08-27-2008, 06:25 PM
Detached requires a wire to bond the sub panel to the main service AND grounding the sub panel. Bonding keeps the two panels at the same voltage potential, which is needed since you can't rely on the Earth to always conduct without resistance.

JohnE
08-27-2008, 10:26 PM
Detached requires a wire to bond the sub panel to the main service AND grounding the sub panel. Bonding keeps the two panels at the same voltage potential, which is needed since you can't rely on the Earth to always conduct without resistance.

If you are running to a detached garage, you can sometimes get away with a 3 wire feeder. As long as there are not metallic paths back to the main house such as a water pipe. You still need to establish a grounding electrode at the detached garage. i.e. 2 ground rods. But a 4 wire feeder ( 2 ungrounded, 1 grounded, 1 grounding conductor.) is what's the norm and is always acceptable, usually required.

If the garage in the op were mine, I'd probably run a 2" conduit to it for power but only use a 50 0r 60 amp supply. Then I could upgrade it if ever necessary easily and affordably.

And given the initial load, whatever service is supplying the house will handle the garage at this point.

JimN
08-27-2008, 10:33 PM
I should have been more specific but your description of a four wire feeder is what I was referring to. The grounded conductor can't be left out if trouble-free operation is wanted, when it's a detached structure.

JohnE
08-27-2008, 10:46 PM
I should have been more specific but your description of a four wire feeder is what I was referring to. The grounded conductor can't be left out if trouble-free operation is wanted, when it's a detached structure.


The grounded (neutral) conductor can't be left out if you want 120V L-N. The grounded conductor can also serve as the grounding (bare or green) conductor in limited circumstances. Again in either case a grounding electrode must be established at the separate structure.

Jim - I don't doubt that you know this, I am just trying to be specific for everyone else reading the thread. I'm an electrician and electrical inspector and have found that even a lot of electricians are not clear on these rules. Other things to consider is whether any local rules or amendments affect the NEC and what year code cycle is in effect. Here in MA we are based on the '08 code, but most of the country is based on '05, and some are on earlier versions.

JimN
08-27-2008, 10:55 PM
Actually, I don't know this as well as I should- calling the neutral the 'grounded' conductor seems counter-intuitive to me and I usually end up calling the bare wire the 'grounded' conductor.

Thanks for the clarification.

JohnE
08-27-2008, 11:39 PM
Actually, I don't know this as well as I should- calling the neutral the 'grounded' conductor seems counter-intuitive to me and I usually end up calling the bare wire the 'grounded' conductor.

Thanks for the clarification.

Grounded conductor carries current. In a 120 Volt circuit the white conductor is the grounded circuit conductor and carries the same current as the ungrounded (black) conductor.

In a 240 Volt circuit the grounded conductor (also known as the "neutral" conductor) carries the imbalance between the 2 ungrounded conductors.

Sometimes in a 240 volt circuit the grounded conductor can double duty as the grounding conductor. But more often the grounding conductor is a separate 4th conductor.

It can get confusing. The electrical forum I'm on gets makes the oil threads here look like child's play.:D

TX.X-30 fan
08-27-2008, 11:56 PM
It can get confusing. :D





....................... 39586 39587

Willski
08-28-2008, 12:03 AM
If you are running to a detached garage, you can sometimes get away with a 3 wire feeder. As long as there are not metallic paths back to the main house such as a water pipe. You still need to establish a grounding electrode at the detached garage. i.e. 2 ground rods. But a 4 wire feeder ( 2 ungrounded, 1 grounded, 1 grounding conductor.) is what's the norm and is always acceptable, usually required.

If the garage in the op were mine, I'd probably run a 2" conduit to it for power but only use a 50 0r 60 amp supply. Then I could upgrade it if ever necessary easily and affordably.

And given the initial load, whatever service is supplying the house will handle the garage at this point.

I'm leaning toward the #6 / 3 wire with an additional ground. As you can tell, I'm no electrician, just doing the trenching and wire laying. I will have someone else make all of the connections. Thanks for all of the help everyone.