Garage Load Center

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Old 09-09-11, 11:30 AM
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Garage Load Center

I am buying a house (close in one week) and the home has an old 1 car 13' x 24' detached garage. The garage is old and too small by today's standards, so I am going to rip it down and build a new one.

Currently, the electrical is fed from an above ground wire, which I plan on getting rid of, running new wire from the house underground to a sub panel in the garage. The new garage will be 24' x 30' and as of right now, I am planning to include about 4 electrical 20 amp circuits (gfci of course), probably 6 - 8 8' flourescent fixtures, 3 outdoor decorative lights, 1 motion activated light, 2 garage doors, and one heater. I want a little wiggle room for the future incase I need a small air compressor (would likely work on 20A existing circuit), or some other type of tool. I have a rough sketch of what I am looking at doing and haven't done all of my homework yet, but have a few questions:

1. What size breaker/wire gauge is recommended for this application?
2. I would guess it would be a better option to run the wire in pvc conduit vs. wire approved for burial? Run will be about 30'
3. Is it a good idea to use GFCI receptacles or just go with a GFCI breaker at the panel?
4. I know/believe it depends on local code cycle, but just wanted to confirm that it is required to connect the ground and neutral busses from sub panel back to the main panel?

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Old 09-09-11, 11:48 AM
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You may want to re-think the idea of eight-foot fluorescent fixtures as I think the eight foot tubes are being eliminated in a year or two.

The GFCI receptacles are about 1/3 the cost of a GFCI circuit breaker. Only the first receptacle in a circuit needs to be GFCI and the rest will connect to the LOAD terminals of that first GFCI.

If you are planning on a electric heater then you first need to do a heat loss calculation. One of the "quick and dirty" methods that are free on the Internet will suffice for a garage/shop area.

PVC conduit is always better than direct burial in my opinion.

Yes, the sub-panel must have the neutral and equipment ground buses separate. The neutral is isolated from the enclosure and the equipment ground is bonded to the enclosure. You need four wires running back to the service panel in the house and you also need at least one grounding electrode (ground rod) at the detached building.
 
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Old 09-09-11, 01:06 PM
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I would install 1-1/4" PVC conduit buried 18" and pull conductors for a 60A panel (#6 hots & neutral, #10 ground). Unless your electric heater is quite large this will be enough for the loads you describe.

These wires could be replaced in the future with a 100A feeder if you ever decide on getting a big machine like a welder. The conduit only adds a few dollars upfront for more protection of the wires and a lot of flexibility down the road. I would also install a second 3/4" or 1" conduit a few inches above in the same trench you can use for phone, data, security system, etc.

Also I agree 100% with Furd about the lights. Avoid any fixtures with T-12 lamps and instead get electronic ballast T-8 or even better T-5 fixtures. They are more efficient, instant-on, put out better light quality and don't have that obnoxious hum or flicker.
 
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Old 09-09-11, 06:13 PM
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To expound a bit, I agree with what has been suggested, but I would also rough the 1 1/4" PVC conduit in under the footing to avoid having the conduit exposed on the outside of the garage.

I don't think fixtures with T12 lamps are even sold any more, but some stores may have some very old stock on sale just to get rid of it, avoid them if that is the case. If you like 8 foot strip or industrial fixtures, go with tandem 8 footers that take 4 foot lamps. The electronic ballasts that come in new fixtures typically are 0 degree rated for use in cold weather.
 
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Old 09-09-11, 08:06 PM
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Joe, I bought an eight-foot twin-tube high output fixture at Big Blue this spring and also a half-case of tubes so that I would have enough for the six fixtures in my garage. There were no shortages of either fixtures or tubes back then but I admit I haven't looked recently. I figure that this will last me until I die and then it is someone else's problem.

I will admit that from a logistical viewpoint (transporting the tubes) four-foot tubes make a lot more sense than eight footers.
 
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Old 09-10-11, 07:13 AM
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I know T12 lamps are readily available, but haven't seen any new T12 fixtures in a while. In fact, I was looking for a T12 high output fixture almost 2 years ago and found a few in old stock at one distributors warehouse. I figure after T12 lamps are no longer manufactured there will be large stocks of lamps for several years, but the price is likely to go up. Reminds me of when they quit manufacturing R-12 refrigerant and it's still available today, but pricey.
 
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