What cable to use...

[Clint]

Hello all....I am getting ready to replace the 60 year old wiring that goes from my house to my detached garage. I recently had the house service upgraded from a 60 amp fuse service to a 200 amp circuit panel, and now want to replace the old wiring going to the garage. The existing wiring goes through an underground conduit from my cellar to the garage. I plan on having a compressor and eventually a welder (automotive stuff...nothing too fancy), and nothing much else out there. My question is; what guage or type of wire should I run out there? I am planning on installing all the breaker panel, but not making the final connections...I'm new at this stuff.

Any help would be greatly appreciated.

[Colbyt]

The size and amps of the welder will determine what you need. That is a big draw.

No welder and for a 50 foot run or less I would think 10/3 wg and a 4 breaker subpanel would be all you needed. That would give you one 220 and

2 20's. Of course you could not use it all at once.

Would not be surprised to see the load calculations for a welder double or treble that wire and box size.

Maybe Doug will give you a better answer.

Colbyt

[Doug Miller]

No way to know that, without knowing the requirements of your compressor and welder. How many amps do they require? And at what voltage? (120 or 240)

How big is the conduit?

[Clint]

No way to know that, without knowing the requirements of your compressor and welder. How many amps do they require? And at what voltage? (120 or

240)

First...thanks for the quick responses. Second, my plans are to make the garage into a place where I can work on my Jeep and change the oil in the car and truck...nothing too extensive. My hopes were to install a 100 amp sub panel in the garage, and have the capacity to do pretty much what I please out there. A 240 welder in the future is not out of the question, so I would definately like to take that into account now. Any compressor would be to run air tools...not a paint booth ar anything like that. The existing conduit looks to be 3/4" or so, and there is already 240 out there to a fuse box.

[Doug Miller]

A 100A subpanel ought to take care of pretty much anything you might want to put there -- welder, compressor, table saw...

For a 100A 240V feeder, you need three 4ga copper wires (type THHN or equiv) for the two hots and the neutral, and one 8ga copper wire, bare, for the equipment ground. And that's going to mean a pretty substantial conduit.

Well, that's going to be a problem. Code limits you to two 4ga conductors in a

3/4" conduit, and, quite frankly, it would be a hell of a challenge to pull even that through a 3/4" conduit of any significant length.

The Code limits you to 6ga copper, maximum, in a 3/4" conduit, for three current-carrying conductors, which in turn limits you to 60 amps, tops. As a practical matter, though, it's going to be pretty tough to pull three of anything, plus a ground, any bigger than 8ga, and even that won't be real easy.

Your best bet looks like installing a larger conduit. Looks like you'd be Code-compliant with a 1" PVC conduit, but I'd sure recommend something a lot larger than that -- 1.5" or bigger -- to make the wires easier to pull.

[Goedjn]

How BIG a conduit? If it's too small, that may limit the size of the conductors you can pull.

[jackson]

snip/

While you are at it running new conduit, make your trench a bit wider and run another piece of 1-1/2" PVC with some pull ropes as well for coax, cat5or6, maybe even fiber.....

[Doug Miller]

To the garage??

[<aemeijers]

Standard guy wet dream- plasma screen to watch the game while working on the car or in the woodshop. I can actually see the utility of having broadband out there, to use a junk PC to look up or order stuff without having to get cleaned up. And for a lot of retired guys, the garage becomes their Sekret Klubhouse, No Girlz Allowed, for when the wife gets tired of having them underfoot and shoos them outside to play.

I'm a simple man- a phone jack and rabbit ears on an old portable TV would do for me. But yeah, an extra pipe and pull rope comes under the heading of 'as long as you have the trench open'. Who knows what currently unknown or exotic technology will become a 'must have' 10-15 years from now.

aem sends...

aem sends....

[Mark Lloyd]

You never know when you&#39;re going to want to use a computer, phone, or TV out there.

[Bud--]

Actually you need 3ga. 4ga is ok for a residential service. This is a feeder.

-- bud--

[Doug Miller]

Yes, I know it's a feeder -- I referred to it as a feeder. (see above)

Refer to NEC 2005 Table 310.15(B)(6) Conductor Types and Sizes for

120/240-volt, 3-Wire Single Phase Dwelling Services

****and Feeders****

Conductor Types RHH, RHW, RHW-2, THHN, THHW, THW, THW-2, THWN, THWN-2, XHHW, XHHW-2, SE, USE, USE-2.

AWG 4 copper is rated at 100 amps, AWG 3 at 110.

It's precisely *because* it's a feeder that 4ga is permitted -- if it were a branch circuit, it would need to be 3ga as you say.

[Goedjn]

He who watch TV while working in shop soon be called "Fingerless Jack".

[Steve Barker LT]

60A in the garage would be more than enough in my opinion. We ran a detached for 30+ years with a 10-3 underground 200 feet away. 200A welder, air compressor, overhead heater, fluorescent lights, bench grinder, etc. Never once did we trip the 30 in the main house, nor did we experience the lights in the garage dimming. Your mileage may vary.

[Steve Barker LT]

Hmm, the desk and pc were the first things into my detached when we started moving. My broad band connection actually starts there and is then wired into the house.

[RBM]

That table only applies to dwelling services and their "main power feeder" not to feeders in general

[Colbyt]

My post to this top post is at the bottom.

For the OP. I am betting on Doug in this contest. I have never seen him give a response that I considered wrong.

Colbyt

[RBM]

No question, Doug is sharp, but I think it's the NEC that is misleading. The table he quoted, says exactly what he said, but the paragraph before that table clarifies that "feeders" actually means the main power feeder between the main disconnect and panel

[Bud--]

Amplifying, the intent is to cover a fedder from a service disconnect-only to a panel with the over current devices. This feeder is not service conductors. and would not normally qualify for using the reduced wire size allowed for service conductors. Since this feeder carries the same current as service conductors, it is allowed to use the same reduce conductor size. 310.15-B-6 continues "For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch circuit panelboard(s). The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity greater than the service--entrance conductors." Residential service wires are allowed to use a reduced wire size because of "diversity" - there are many different kinds of loads and not everything will run at once. It is not known if feeders in general will have that diversity.

Doug is sharp, but we all make mistakes and the NEC is full of possible gotchas.

-- bud--

[Doug Miller]

"For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch circuit panelboard(s)." [Art. 310.15(B)(6)]

Note the deliberate inclusion of the plural in feeder(s) and panelboard(s).

Since the feeder in question runs between the service entrance panel (which, in a single family dwelling, is the location of the main disconnect) and a branch circuit panelboard, it appears to me to qualify.

As always, though, the local inspection authority has the final say, and it would be best to ask their opinion -- since, in the end, neither your opinion nor mine matters at all if the local inspection authority has other ideas.