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Old 08-27-2012, 08:36 AM   #1
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Garage sub panel plans


Hi, I am new to this site and would like someone to review my garage sub panel project. I have 200A service at the main and would like to install a 125A sub panel to feed my attached garage, a small bathroom and washer/dryer. Items in the garage I plan on powering include a welder, lift, general electric tools, garage door opener and lighting. My plans include the following:

1- Install a 125A sub panel in the garage w/a 125A breaker in the main lug panel.

2- Use 1 AWG copper for my two hots and neutral. Use 4 AWG for ground (not sure if I should use insulated or bare) THN in 1 1/4" EMT conduit ran in the basement, (properly connected to the main and sub panel) attached to the ceiling joists. I already have holes that penetrate the garage area from older unused plumbing.

I would like hear what others think about my plans.

BTW - this is a great site, I have been reading prior to joining.

Thanks in advance,
Paul

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Old 08-27-2012, 08:37 AM   #2
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Garage sub panel plans


Do you really need 125 amps? You can save some money by just going with a 90 amp feeder...and running #2 al. SER cable...

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Old 08-27-2012, 09:23 AM   #3
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Garage sub panel plans


I was thinking about just running SER cable, but can that be run under joists in an unfinished basement? I thought it's similar to NM cable, where it needs to be protected. That's why I was proposing conduit & THHN.

If I used #2 SER, I should be able to go with a 90A breaker, correct?

I am not sure if 100A would be enough, based on everything I want to power;

1- Garage tools, vehicle lift, welder, compressor, misc. tools and lighting

2- Washer/dryer

Your thoughts?
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Old 08-27-2012, 09:36 AM   #4
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Garage sub panel plans


Quote:
Hi, I am new to this site and would like someone to review my garage sub panel project. I have 200A service at the main and would like to install a 125A sub panel to feed my attached garage, a small bathroom and washer/dryer. Items in the garage I plan on powering include a welder, lift, general electric tools, garage door opener and lighting. My plans include the following:
Quote:
1- Install a 125A sub panel in the garage w/a 125A breaker in the main lug panel.
I highlighted a couple of your big enrgy users. A typical stick welder set on high amperage output might draw 40 or so amps at 20% duty cycle. electric dryer around 27 amps on high heat.

These two may operate at the same time and would be your highest load IMO.

I agree with stickboy no need for 125 amps that's overkill. Install a 100 amp panel. Choose one that gives enough spaces for your branch circuits.

Quote:
2- Use 1 AWG copper for my two hots and neutral. Use 4 AWG for ground (not sure if I should use insulated or bare) THN in 1 1/4" EMT conduit ran in the basement, (properly connected to the main and sub panel) attached to the ceiling joists. I already have holes that penetrate the garage area from older unused plumbing.
Don't need a ground wire if your using EMT, the metal conduit will be your equipment ground. BTW #4 ground is not necessary a #6 would do but I would run cable if I was running a ground wire no need to have metal conduit and a ground wire. I used to think run the ground wire for added integrity in case the emt comes apart but I no longer think that way.

Use 3 awg copper for 100 amps ( 2 awg might be all you can find at the big box) Aluminum (it will be larger awg) will save you cost nothing wrong with copper though....

Use this diagram as a guide ... it's correct but your situation may differ so be sure to review it with a qualified person. Pay particular attention to separation of neutral and ground in your sub-panel. In your case using EMT you will have 3 conductors (H-H-N) in the pipe and the EGC will be your conduit. Make sure you make it up tight.








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Old 08-27-2012, 09:46 AM   #5
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Quote:
Originally Posted by pcarpe01 View Post
I was thinking about just running SER cable, but can that be run under joists in an unfinished basement? I thought it's similar to NM cable, where it needs to be protected. That's why I was proposing conduit & THHN.

If I used #2 SER, I should be able to go with a 90A breaker, correct?

I am not sure if 100A would be enough, based on everything I want to power;

1- Garage tools, vehicle lift, welder, compressor, misc. tools and lighting

2- Washer/dryer

Your thoughts?
I didn't see the compressor in your first post but I still don't see more than 100 amp rating necessary. Determine the things that will be running simultaneously and at what load. Equipment name plates will give you maximum loads. Your feeder rating should be equal to or greater than what you calculate ... just don't be unreasonable with what you calculate.

Cables of the size we are talking can be attached to the bottom of joists.


Quote:
If I used #2 SER, I should be able to go with a 90A breaker, correct?
Yes the ampacity of SER excludes NEC 334.80 and can be used at 75C rating except where run in insulation.

90 amp breaker is probably a special order at the big box but a good elec. supply should have one.

In your main panel there should be listed the maximum size branch/feeder breaker you may use. At a 200 amp rating you should be fine

Last edited by Stubbie; 08-27-2012 at 09:58 AM.
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Old 08-27-2012, 04:37 PM   #6
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Garage sub panel plans


Quote:
Originally Posted by pcarpe01 View Post
I was thinking about just running SER cable, but can that be run under joists in an unfinished basement? I thought it's similar to NM cable, where it needs to be protected.
You can run it under the joist, without any added protection.

Quote:
Originally Posted by pcarpe01 View Post
If I used #2 SER, I should be able to go with a 90A breaker, correct?
Yes
Quote:
Originally Posted by pcarpe01 View Post
I am not sure if 100A would be enough, based on everything I want to power;

1- Garage tools, vehicle lift, welder, compressor, misc. tools and lighting

2- Washer/dryer

Your thoughts?
I dont see you having any issues... If you hired me, this is exactly what you would get.

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