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Old 05-10-2011, 03:33 PM   #1
binovc
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Default Sub electric from house, or add a new service?

Hello - new to this forum. Looking for advice on adding electric to a garage we built last summer in Billings, MT.
I am currently renting out the house on this property, but I needed to build a garage which is separate from the rental. The renter will not have access to the garage. However in the future I may move back into the house.
So I'm looking for comments if I should run power from the existing house panel, or have a new service installed completely separate from the house.
If I run a new service, I would have to pay a separate monthly service charge to the power company. If I run power from the house, I would want to have some way to figure how much electricity was used in the garage so I could reimburse the renter. Is there a meter that I can install so I know how much electricity is used just in the garage? Or??
Thanks!
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Old 05-10-2011, 04:19 PM   #2
Charles (in GA)
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Default Re: Sub electric from house, or add a new service?

You can purchase electric meters, look on the internet. What I would do is put a separate service on the garage (providing the local building codes allow it, and the power company allows it) and later, if you do move back in the house, you can have the power company cut off the service and then you can supply it from the house.

Issues:

1) many power companies will not put a separate meter on a non-residence located on residential property. If they do, many want to bill you at commercial rates.

2) many AHJ (Authority Having Jurisidiction, the building inspectors), will also not allow you to have a separate service on residential property, it reeks of a unlicensed, or underground business and this is their way of preventing it.

3) even if the house is not occupied you will end up paying for power for it to allow for repairs, painting, heat, etc, while you are between renters.

On the good side:

1) separate power is nice, no problems with the computer or TV when the welder or compressor, plasma cutter, etc, it operating. Your renters (or your wife if you move back in) won't complain.

2) if you lose power in the house, meter failure, service entrance cable failure, or the like, or you need to shut down house electrical to do work on the panel board, you have a second source of power to run the fridge and a few lights, just string out a couple of 12 ga extension cords from the garage to the house.

Charles
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Old 05-11-2011, 02:04 PM   #3
binovc
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Default Re: Sub electric from house, or add a new service?

Thanks for your insight Charles.
There is no issue with the inspector or the power company on having a separate service, and the pc would charge us the residential rate, not commercial. I guess the only downside is having to pay the additional $10 (or so) /mo for the service, plus whatever connection charge is involved.
If I come from the house, it sounds like I could either run a 4-wire from a breaker, or possibly come straight off the house disconnect ("unlimited tapped conductor"?). I would run underground either way approx 45'. Question - what size wire (copper) and conduit needed for 100 amp panel in garage? 200 amp?
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Old 05-12-2011, 08:09 AM   #4
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Default Re: Sub electric from house, or add a new service?

Quote:
Originally Posted by Jim1 View Post
For a 100 amp service you should run three #4 copper conductors, two hot and one neutral. And a #8 grounding conductor.

1 1/4 PVC SCH-40 conduit should do the trick. Buy one stick of PVC SCH-80 to use to come out of the ground and into the house and garage box after you cut it to legnth.
Please consult the NEC , the above wire sizes are undersized & does not comply with code.
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Old 05-12-2011, 08:20 AM   #5
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Default Re: Sub electric from house, or add a new service?

#4 would be good for a 100 amp service, but your right, to run 100 amp from your house panel it would have to be #2 copper.

Three #2 THHN or THWN copper conductors, two hot and one neutral with a #8 equipment grounding conductor.

1 1/4 PVC to run them in.

If you run the grounding conductor to your garage with your phase conductors you will have to keep the ground and neutral separate in your garage panel. Bond the grounding conductor to the garage panel but not to your neutral. Your neutral bus will be "floated," only neutrals will be attached to the neutral bar and grounding conductors to the ground bar.

Last edited by Jim1; 05-12-2011 at 10:02 AM.
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Old 05-16-2011, 05:14 PM   #6
binovc
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Default Re: Sub electric from house, or add a new service?

Thank you for the sizes. I don't want to buy a copy of the NEC, and I don't think it's readily available on the internet (??), but if one is available you could point me to...
I have sent the inspector a message asking if "double lugging" is allowed (either off the house meter or off the disconnect). This would be easier than running a 100 amp line off my house main panel. From my reading, it sounds as though double lugging is allowed in some areas, but not others. If allowed, and I use 100 amps in the garage, I'm asuming the #2 THHN or THWN copper conductors remains valid, but instead of 4 conductors it would require 3 (2 hot, 1 neutral), with the ground placed at the garage (a ground rod that also connects to the rebar in the floor), and not separated from the neutral at the panel.

Jim1, you mentined "If you run the grounding conductor to your garage with your phase conductors". Excuse my ignorance, but how else would I run that conductor?
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Old 05-16-2011, 05:31 PM   #7
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Default Re: Sub electric from house, or add a new service?

I have a seperate service for my garage, it's billed separate too. Since it was formerly a service station, it had a 200 amp service in it. The power company bills it as "small general service".
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Old 05-16-2011, 09:58 PM   #8
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Default Re: Sub electric from house, or add a new service?

There are two ways to do it. Run the grounding conductor from the source (200 amp house panel) with your phase conductors, four wires going out to the garage. (my recommendation) Or get your ground at your garage panel, like you're talking about. If you did it that way you would only run three wires from your house, no ground wire. Then at your garage panel drive a ground rod and bond your ground bar and your neutral bar together along with the panel case. In the first instance you must have a "floated" neutral, and for the second you must have a "bonded" neutral.
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Old 05-16-2011, 10:46 PM   #9
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Default Re: Sub electric from house, or add a new service?

Quote:
Originally Posted by Jim1 View Post
There are two ways to do it. Run the grounding conductor from the source (200 amp house panel) with your phase conductors, four wires going out to the garage. (my recommendation) Or get your ground at your garage panel, like you're talking about. If you did it that way you would only run three wires from your house, no ground wire. Then at your garage panel drive a ground rod and bond your ground bar and your neutral bar together along with the panel case. In the first instance you must have a "floated" neutral, and for the second you must have a "bonded" neutral.
you pretty much cant run a 3 wire feeder to a subpanel anymore.

even with a 4 wire feeder, you still need grounding electrodes -UFER if there is a footing with rebar in it or two ground rods.
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Old 05-16-2011, 10:48 PM   #10
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Default Re: Sub electric from house, or add a new service?

In Newport News VA, the electrical inspector wont allow a separate service for residential. He claimed something about the fire company needs to know only one panel is powered not 2 separate sources coming in.
So we added 400 amp service. The Dominion power company gives you the meter box free and with all the internal bars there is no double lugging.
The old 200 amp service was disconnected and the old house main breaker panel became a sub panel. Had to have a 200 amp fused disconnect switch for it and we ran that big chunky 4/0 with 2 hots, a neutral and ground between the fused disconnect and the old house panel.
Ran it threw the structure and walls, threw the attic, it was a tough job pulling that long cable and figuring out a path.
ground rods were disconnected at the old panel and 2 new copper rods put in at the new panel.
We got the disconnect off ebay for $80 and it was used and has been fine. It is an older heavy duty 3 phase thing with a big aluminum cast handle. It was skinnier and taller than the new modern looking ones. The inspector passed it but told us we are supposed to buy new parts.
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Old 05-17-2011, 03:43 AM   #11
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Default Re: Sub electric from house, or add a new service?

youre lucky he passed that. You have to use new material unless the AHJ gives you an exception which is usually reserved for things like fancy switchgear, motor control centers, things like that.
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Old 05-19-2011, 01:28 AM   #12
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Default Re: Sub electric from house, or add a new service?

Make life easy on yourself and your wallet and run a seperate service. Depending on your power company they usally only charge a small service for a site review and typically give you a length allowance, say 100' or so.

It keeps that structure seperate from your home making it overall safer and worry free.

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Old 06-01-2011, 11:20 AM   #13
binovc
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Default Re: Sub electric from house, or add a new service?

Still appreciating the comments - thanks. Getting closer to project date.
I still have not decided against installing a separate service to the garage (and looking at prices of #2 copper may be a much cheaper alternative!). But if I come off the house (main panel, located in kitchen), I will run the conductors down to a basement, then along the ceiling, then out a wall, then down to the trench to the garage.
I assume I need to run the THHN/THWN conductors from the main panel in conduit. Can it be the same PVC conduit that I would run in the trench, or do I need to use metal conduit inside?
At the garage, do I need a disconnect on the exterior wall, or a main breaker on the 100A sub panel, or both?
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Old 06-01-2011, 11:58 AM   #14
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Default Re: Sub electric from house, or add a new service?

I completly disagree with everyone that has recommended a seperate service.

I also disagree with attempting to submeter the load.

My reasoning:

Many electrical companies (like most of them around me) are changing their rate structures to Fixed Variable Rates. Essentially this requires them to recover ALL of their fixed costs through the customer charge and only collect the variable cost producing and transporting whatever power you use as a commodity charge. The effect of that has been the base customer charge skyrocketing from the $10 range to almost $50/month/meter for residential customers.

This is a national trend and I would expect it to continue.

My reasoning against submetering is that most utility trariffs won't allow it. It opens up you to liability with a potential renter, as you are now their power provider NOT the power company. And, it will open a big can-o-worms in the future with what you charge them for the power.

Just charge extra in the rent to cover a healthy increase in your power bill and let it go.

My 2-cents.

Phil
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Old 06-01-2011, 12:01 PM   #15
Charles (in GA)
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Default Re: Sub electric from house, or add a new service?

PVC conduit is fine inside, use the heavier schedule 80 if exposed where it might get damaged (doubtful in a basement ceiling however, I'd just use sch 40).

Your choice on the disconnect, inside or out on the garage. Probably the cheapest way is to buy a main breaker panel kit, you can get 150 amp I know for sure, comes with main breaker and a selection of breakers. Good way to get started. I used a meter socket outside that had a 200 amp disconnect in it, and then a 40/40 200 amp main lug panel inside. You can stand in the doorway and touch both panels, no sense putting one inside when local rules required me to have one outside.



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Old 06-01-2011, 12:09 PM   #16
Charles (in GA)
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Default Re: Sub electric from house, or add a new service?

Quote:
Originally Posted by HoosierBuddy View Post
I completly disagree with everyone that has recommended a seperate service.

I also disagree with attempting to submeter the load.

My reasoning:

Many electrical companies (like most of them around me) are changing their rate structures to Fixed Variable Rates. Essentially this requires them to recover ALL of their fixed costs through the customer charge and only collect the variable cost producing and transporting whatever power you use as a commodity charge. The effect of that has been the base customer charge skyrocketing from the $10 range to almost $50/month/meter for residential customers.

This is a national trend and I would expect it to continue.

My reasoning against submetering is that most utility trariffs won't allow it. It opens up you to liability with a potential renter, as you are now their power provider NOT the power company. And, it will open a big can-o-worms in the future with what you charge them for the power.

Just charge extra in the rent to cover a healthy increase in your power bill and let it go.

My 2-cents.

Phil
You got it backwards................

He would be submetering to himself from the renter's power.

Biggest issue here is the renter might not want to front the extra money for a larger utility bill, but he would get it back in "adjusted" rent. Put the meter inside the garage and the utility would not even know about it, much less care. Put a clipboard on the wall next to the meter and read it every month about the same time the utility reads the meter for the renter, do the math and tell the renter how much the garage used. Round it up a buck or two to compensate for using his money.
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Old 07-07-2011, 03:29 PM   #17
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Default Re: Sub electric from house, or add a new service?

Project complete! What I ended up doing:
I found that the meter that feeds the house not only has a disconnect breaker, but also a second unused breaker co-located in the same pannel. The inspector said that would be acceptable to use, which greatly simplified the process as I did not have to figure out how to run the power off the pannel located inside the kitchen (ie connecting PVC to the pannel, and running it out of the house, etc). The run from the meter box to the garage was a pretty straight shot through the yard, just requiring an 18" trench.
After speaking with the power company I found out it would cost a minimum of $650 for them to connect up to a weatherhead, and the wiring between weatherhead and meter had to be done by an electrician. Also the monthly service charge would have been $16.
I completed the project (running the wiring from the house) for right around $600, so it was really a "no-brainer". I elected to use aluminum for the 2 hots and neutral conductors (2/2/4). Much cheaper than copper (I could have used 4awg copper as it turned out, vs 2awg). I was hesitant to use aluminum, but it sounds like that is the most common. I used 8awg copper ground to the garage, and 12awg copper to wire the inside circuits for plugs and lights.
I will be getting a usage monitor to attach to the garage breaker pannel so that the renter can be reimbursed for any electric usage (which would be very minimal in this case - 4 flourescent fixtures and a door opener, garage currently used for storage only).
Hope to post some pictures when I can. Thanks again for all the info that got me started!
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Old 07-07-2011, 06:13 PM   #18
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Default Re: Sub electric from house, or add a new service?

as far as submetering, not being allowed to is a falsehood. you can submeter but you are only allowed to recover your cost for the energy. You cannot make any money off it.
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Old 07-07-2011, 07:54 PM   #19
Charles (in GA)
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Default Re: Sub electric from house, or add a new service?

Glad to see it worked so well for you! Don't you like it when a plan comes together?

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