Surface mount garage/shop wiring Q?

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  #1  
Old 07-13-05, 09:17 PM
m_adkins
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Surface mount garage/shop wiring Q?

I need some advise on how to procede on adding additional electrical survice to a finished and insulated garage/shop. The garage is below a second story so I suspect that there is snsulation in the ceiling as well. The shop is for woodworking. I need at least four 220 volt receptacles and a myriad of 110 volt.

I will create a surface mounted sub-panel near the exterior main panel on the wall of the garage. I guess I'll have to expose the floor of the main panel for the panel-to-panel connection.

I presume that surface mount is the most cost effective way to go. Shall I do metal or schedule 80 pvc?

I presume I will be using THHN wiring.

I want a sub-panel with a main breaker since the mains are outdoors. Anyone want to suggest a mfg/model number? I want the ability to add lots of circuits. A minimum of 60 amps will be required, maybe more.

Also, lighting? I presume that I cannot use flush mount fluroscent fixtures as the ceiling is also a fire break for the second story. I think I need to use surface mount. Anyone know what the california building code says?

Please comment if another approach is better than what I have proposed.

I will be pulling a permit for this work and if needed I can call an electrician for anything over my head. I don't have much problem working with electricity but this would be my biggest and most complex job.

I can't comment on what kind of main panel is installed as we need to get through escrow first. Obvoiusly we are planning at this stage...
 
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  #2  
Old 07-14-05, 09:55 AM
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I prefer EMT (thinwall metal conduit) in garages and shops and armored cable where conduit is impractical.

I would put a 100A subpanel in the shop if you know that you are going to use at least 60A. Consider getting a large 200A 40 space panel and only feeding it with 100A for now. That will give you plenty of room for circuits and a larger serivce if the shop ever expands. Perhaps you'll want A/C out there, a welder, etc. Another consideration is if your house service can handle an additional 60A. You'll need to do a load calculation to see if a service upgrade might be in order also.
 
  #3  
Old 07-14-05, 10:32 AM
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The most practical Wiring Method for your installation is EMT in 1/2" & 3/4" sizes.

Supporting the runs of EMT across the finished ceilng can be done easier by using 3/4" "B-Line" support-channel. The 3/4" "B-Line" is first fastened to the ceiling at rite-angles to the "run" of EMT, and then each lenth of EMT is clamped into the "B-Line" as it "runs" across the ceiling.

Let's say you need a "bank" of 10 seperate EMT's to extend vertically up the wall from the panel, and then across the ceiling. You will first fasten the "B-Line" to the ceiling in lenths that will exceed the "width" formed by the "bank" of 10 EMT's "side-by-side", allowing space between the EMT's for the clamps.

At some point along the ceiling run, some of the individual "runs" will branch off to the Left or Right, reducing the "width" of the "B-Line".

Lets say you need 4 runs of EMT to extend verticaly from the panel to the ceiling, and then extend horizontally across the entire lenth of the ceiling to the opposite wall, and then extend down .These 4 will be the "center" of the bank and are the first to be implaced.

Next, 2 runs across the ceiling for 50 ft, 1 branching off to the Left, and the other to the Right-- these implaced next.

Next, 2 runs 40 ft with Left/Right branches ,then 2 30 ft runs.

If this is a Single-Phase system, and you wire with 3-wire "home-runs", it may be more simple to have only one 3-wire "home-run" in each emt, than two H-R's. = 6 wires per emt. So much depends on the relative location of the connected loads in deciding on the best wiring arrangement.

Good Luck & Enjoy the Experience!!!!!!!!!!!!!!
 
  #4  
Old 07-14-05, 12:24 PM
m_adkins
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Thanks so far.

Don't know what b-line is, but I'd assume its that "C" channel type stuff used for attaching conduit to surfaces.

The system is definitely single phase, but I'll have a few 220 volt drops. My understanding is that you are limited to a single device (wall plug) per circuit breaker.

I would like to put as much wire in the conduit as is allowed to cut down on the amount of EMT required.

I was thinking of running the EMT along the walls, but it does make much more sense to run it along the ceiling until close to the required location. The exception would be a run of several quad boxes for the workbench. I'd run two circuits together alternating outlets if that is allowed.

Obviously I need to diagram the system in fairly short order. I should be able to get in the house sometime next week to diagram the garage.

Right now I would be leaning to a 100 amp subpanel just to get the circuit breaker space. This also would allow the use of the panel for a future Spa if the main panel has no slots. (Might be able to pull power from whereever the pool is connected for the spa though). If you happen to be able to suggest a specific panel I'd appreciate it. Square D seems to be the best. I looked on-line but couldn't figure out what to get. I guess I'd be looking at something without a separate mains and use one of the breaker locations for a backfeed to the main panel. (did I get the lingo right? )
 
  #5  
Old 07-14-05, 02:39 PM
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There is no limit on the numbers of outlets on Branch-Circuits rated between 15- 50 amps, provide the connected-loads do not exceed the B-C rating.

If you have will have any B-C's in the 30-50 amp range, please know that the ratings of the connected devices becomes important.

Square D is an excellent choice.

Aside from "general-purpose" 15 & 20 amp receptacle-circuits,If you can submit a list of specific loads, please do so, specifying both the voltage and current values.

Good Luck & Enjoy the Experience!!!!!!!!!!!
 
  #6  
Old 07-14-05, 09:15 PM
m_adkins
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I will not particularly enjoy the experience, but it will be a good learning experience.

I will do some load checking. I know the Table saw will use 30 amps. The duct collector will use probably 20 depending on what I buy. Both at 220 volts. Lighting will be maybe 1000 watts or about 10 amps. Air compressor will be 12 amps at 110 v. Thats probably the maximum simultaneous load and probably fairly conservative. Other loads will be there but not when other equipment is running.
 
  #7  
Old 07-15-05, 08:34 AM
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Originally Posted by m_adkins
This also would allow the use of the panel for a future Spa if the main panel has no slots. (Might be able to pull power from whereever the pool is connected for the spa though).
Spas usually pull 50 or 60 amps -- you should definately plan for that large load if you think you'll use it.
 
  #8  
Old 07-15-05, 02:01 PM
m_adkins
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Originally Posted by ibpooks
Spas usually pull 50 or 60 amps -- you should definately plan for that large load if you think you'll use it.
The Girl Friend wants a spa. Probably gonna happen so I will provide for it.

For operating cost, I'd rather go natural gas if I can plumb it up and it doesn't add too much to the initial cost.
 
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