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Old 11-08-2008, 01:59 PM   #1
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Service line from house to garage.... question


I built a small garage/polebarn which sits outside my home - - roughly 65 feet from my house.

The distance from my home's 150 amp service panel to the garage's 100 amp service panel (for a hookup) is roughly 127 feet.

I have 2.5" pvc conduit run @ 27" below grade from the panel in my garage to inside my basement... so the service line wiring won't be exposed to bare earth.

I plan on using my garage for light duty work... mainly using it for interior/exterior lights, interior/exterior outlets.... maybe a small air compressor on occasion, portable table saw on the rare occasion, shop vac once in a while...perhaps a kerosene heater in the winter... shop vac.... no welders..... just simple homeowner stuff. Maybe run a circular saw rarely or a table-top grinder.

So, anyway... I have a few electrician friends that have given me advice on the service line from the house to the outside garage building... a few have said that for what I will use it for; #4 Copper SER wire (3 conductors and 1 ground wire) would suffice.

Another electrician said I should use #2 Copper SER.

One of the electricians said he would just use #2 Aluminum SER (because it's cheaper and works fine he says).

What is your opinion??

I may eventually install a small natural gas heater hanging from the ceiling... but I don't think those draw too many amps.

What would be the thing to do?

Thanks for your advice.

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Old 11-08-2008, 02:18 PM   #2
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Service line from house to garage.... question


You cannot legally pull SE type cable into an underground conduit. You need 4 wires: 2-hots, a neutral and a ground. You need a disconnect at the remote location, which can simply be a main breaker in the subpanel, and you need to drive a couple of ground rods at the location and connect them to each other and the ground bar in the sub.

For 100 amps, you should use at least #3 copper for the hots and neutral, and #6 for the ground. For such a distance, you might consider #2 for the hots and #4 for the ground.

Since you are here asking, you obviously don't have much faith in your electrician buddies, and rightly so. They have given you bad advice on wire choice. But, seriously, remember to keep the grounds and neutrals separate at the subpanel, and you may need to purchase a ground bar for your panel, because alot of manufacturers don't include one in a main breaker panel.


Last edited by InPhase277; 11-09-2008 at 01:15 AM. Reason: 'Cause I'm an idiot..
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Old 11-08-2008, 02:37 PM   #3
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Service line from house to garage.... question


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Originally Posted by Todd-sta View Post
I may eventually install a small natural gas heater hanging from the ceiling... but I don't think those draw too many amps.
We put one in my dads work shop last year, they draw 2-5 amps at the most for the blower fan. They use no more power than a few spot light bulbs. Atleast that is the case with the one we had and all of the ones I researched. We got the modline natural gas HotDawg heater. The largest unit they make draws a max of 4.7amps.

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Old 11-08-2008, 03:24 PM   #4
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Service line from house to garage.... question


Thanks Inphase....and all.

Check out the pictures of the project I added!

Ok, so I should spring for 3 #2 wires and a #6 ground.

If I do this - - will I need to extend my pvc conduit from where it enters the house (basement) all the way to the house's panel?

They told me if I use SER, then I wouldn't need conduit all the way to the house's panel once it entered the house from the buried conduit going from the house to the garage....

Best way to feed them? Should I run a snake through the pvc conduit and tie all 4 wires to the end and pull it back on through?

Thanks for all your expert advice.

Last edited by Todd-sta; 11-08-2008 at 03:45 PM.
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Old 11-08-2008, 07:57 PM   #5
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Service line from house to garage.... question


Quote:
Originally Posted by Todd-sta View Post
Thanks Inphase....and all.

Check out the pictures of the project I added!

Ok, so I should spring for 3 #2 wires and a #6 ground.

If I do this - - will I need to extend my pvc conduit from where it enters the house (basement) all the way to the house's panel?

They told me if I use SER, then I wouldn't need conduit all the way to the house's panel once it entered the house from the buried conduit going from the house to the garage....

Best way to feed them? Should I run a snake through the pvc conduit and tie all 4 wires to the end and pull it back on through?

Thanks for all your expert advice.
You can either extend the pipe all the way to the service panel, or land it in a junction box and use SER from there. But as I said, SE-type cable cannot be pulled into an underground conduit. You could also reduce to a smaller conduit once you get to the house, because it will be alot easier to get it into the panel than a 2.5".

And for such a long run, what I do is tie a plastic grocery to the end of a string and use a shop vac to suck it through. Then tie the wires onto the string and pull. Use some lube for ease.
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Old 11-08-2008, 09:14 PM   #6
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Service line from house to garage.... question


Thanks Inphase...

Couple more questions...

  • Is it common/safe to connect the individual wires to a SER run as you describe inside a house? I'm a little paranoid and want to make sure there is no chance of fire, etc. This seems like a good way to go, because I think I'd play heck trying to get a conduit to - and into my house panel. And there is no problem with 'code' doing this method?
  • Is the reason they don't allow SER wire in underground conduit due to heat buildup underground with no way to dissipate the heat? Just curious...?
Thanks again!
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Old 11-09-2008, 12:36 AM   #7
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Service line from house to garage.... question


Quote:
Originally Posted by Todd-sta View Post
Thanks Inphase...

Couple more questions...

  • Is it common/safe to connect the individual wires to a SER run as you describe inside a house? I'm a little paranoid and want to make sure there is no chance of fire, etc. This seems like a good way to go, because I think I'd play heck trying to get a conduit to - and into my house panel. And there is no problem with 'code' doing this method?
  • Is the reason they don't allow SER wire in underground conduit due to heat buildup underground with no way to dissipate the heat? Just curious...?
Thanks again!
For the first question... yes. IF you make the connection correctly and in an enclosure.

The second: SER is simply not listed for use in that manner. Is it a huge deal? Not really. The cable is rated for "wet locations", and an underground conduit is indeed a wet location. However, the cable is also listed as being for use above ground. Also, it is just easier to pull individual conductors than a cable like SER. The jacket on that stuff is like a cat's tongue.

Having said all that, if you have a 4-wire type SER cable, and the ground is insulated, an inspector may allow it to be installed in a conduit. I wouldn't do, and would not recommend you do it. If it were me, I would pull the individual conductors, and change to a copper SER cable in a junction box once in the basement.
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Old 11-09-2008, 02:46 PM   #8
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Service line from house to garage.... question


Thank you VERY much InPhase!! You've been a great help.

Last question and then I'll let this go....

What are your thoughts on Aluminum Wire verses Copper? I know Aluminum is a lot cheaper, and I don't want trouble just to save some money... but is it a viable alternative in this situation... or would you go copper?

Thanks !
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Old 11-09-2008, 03:24 PM   #9
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Service line from house to garage.... question


Quote:
Originally Posted by Todd-sta View Post
Thank you VERY much InPhase!! You've been a great help.

Last question and then I'll let this go....

What are your thoughts on Aluminum Wire verses Copper? I know Aluminum is a lot cheaper, and I don't want trouble just to save some money... but is it a viable alternative in this situation... or would you go copper?

Thanks !
My feeling, and what I have been told by others here, is if you can afford to run copper, go for it. I think the connections are more reliable on copper and have less problems. For service cable, millions of homes use AL without any problems.

Years back they were wiring many homes inside with AL to outlets, lights, ovens, etc to save money. There turned out to be many problems with the connections, and there were a lot of fires caused by it. This was more of a connection problem from my understanding, and is not nearly as much of a problem with Service Cables.

If the cost isn't a huge imposition for you, I would just use copper. When I put in my new service upgrade to 200A, if I can get them to put the meter where I want it, I will have to run about 70 feet of wire from ther meter, 2/0, I am planing on using coper (but expect it to be well over $1,000 for the wire). But I realize this can get very expensive. If your running #2 copper x 130 feet X 3 wires = 390 feet X $1.78 per foot (current home depot price) = $694. Ouch.

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Old 11-09-2008, 06:47 PM   #10
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Service line from house to garage.... question


Thanks Jamie....

I'd prefer copper, and that's what I think I'll go with... but pricing out a few places - it came to $1200 roughly for 135 foot of #2 X 3 wires (not including the ground wire - are the ground wires cheaper ?)

But I haven't checked Home Depot yet.

If I can get it for the price you stated - I'm all over that!!

Aluminum is very tempting.... but I know you have to use a thicker wire to get the same benefits as a thinner copper....

Thanks for your input.
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Old 11-09-2008, 07:28 PM   #11
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Service line from house to garage.... question


Just my opinion, I've never used copper for a feeder, only branch circuits, You are not getting a better job, especially in residential, but to each his own, Its your pad and your wallet.
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Old 11-09-2008, 07:37 PM   #12
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Service line from house to garage.... question


Quote:
Originally Posted by Todd-sta View Post
Thank you VERY much InPhase!! You've been a great help.

Last question and then I'll let this go....

What are your thoughts on Aluminum Wire verses Copper? I know Aluminum is a lot cheaper, and I don't want trouble just to save some money... but is it a viable alternative in this situation... or would you go copper?

Thanks !
If this were my house, I would use aluminum. But if you hired me, I'd prefer to use copper. You just have to upsize the wire a little for aluminum. But I haven't encountered any problems with properly installed al conductors. So, like Chris said, it's your wallet, do whatever makes you feel better.
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Old 11-09-2008, 08:02 PM   #13
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Service line from house to garage.... question


Ok... thanks guys....

So you would actually recommend ALuminum feeders from the house to the garage Panels?

If this is the case... to get the "capacity" of a #2 copper, wouldn't I have to get a #1 Aluminum? Is that going to get huge and crowd my 2.5" conduit pipe underground?

And... is that a tough one to connect to the main and sub-panel breakers?

InPhase - just curious why you would prefer to use copper if you were doing it for someone else - is it easier to work with?

What's your recommendation on wire gauge? You mentioned earlier that you would go with at least a #3 copper - possibly a #2 copper.

Thanks again for all your help guys! Very generous of you to take the time to 'educate' me on this. I hate to run the wrong thing.
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Old 11-09-2008, 08:32 PM   #14
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Service line from house to garage.... question


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Originally Posted by Todd-sta View Post
Ok... thanks guys....

So you would actually recommend ALuminum feeders from the house to the garage Panels?

If this is the case... to get the "capacity" of a #2 copper, wouldn't I have to get a #1 Aluminum? Is that going to get huge and crowd my 2.5" conduit pipe underground?
Crowding? No way. You could jam 4-4/0 in there with room to spare. #1 aluminum is rated for exactly 100 A. To prevent voltage drop, you can go a size bigger, to 1/0. But it really isn't necessary, as you will probably never load it enough for the effect to be noticeable.

Quote:
And... is that a tough one to connect to the main and sub-panel breakers?
Maybe the main panel, because of the other wiring there. But not in the sub.

Quote:
InPhase - just curious why you would prefer to use copper if you were doing it for someone else - is it easier to work with?
Just because I know that copper is old reliable. It doesn't have the same potential problems that aluminum has. Namely oxidation and strands breaking off due to improperly stripping the wire. And the larger size required. And I'm a commercial/industrial guy from way back, and we never used aluminum. I just like good ol' copper, especially for customers.

I, being an electrician, wouldn't hesitate to use aluminum for a feeder on my own property. In fact, my shop is fed with al. But copper is more forgiving to the novice. Carefully installed, with the antioxidant goop, al is ok.

Quote:
What's your recommendation on wire gauge? You mentioned earlier that you would go with at least a #3 copper - possibly a #2 copper.

Thanks again for all your help guys! Very generous of you to take the time to 'educate' me on this. I hate to run the wrong thing.
For just a minimum, #3 copper or #1 aluminum. For heavy loads, to reduce voltage drop, #2 copper or 1/0 aluminum.
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Old 11-09-2008, 09:09 PM   #15
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Service line from house to garage.... question


Your 65' away, you would get # 2 Al, backed with a 90amp breaker if you hired me. Your house does not draw that much. I only do residential, so I have a different outlook than the commercial guys here.

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