Choosing a Sub-Panel


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Old 05-30-05, 05:50 AM
W
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Choosing a Sub-Panel

I now have everything in place to go get the permits for my sub-panel in my detached garage. I calculated all the load requirements and designed all the circuts. The only thing left is to pick the sub-panel.

Here's a summary of what I will be installing:
  1. 30 Amp Service from Main Breaker in Basement
  2. 1 15A, 120 V circuit containing 5 GFCI outlets spread throughout the garage, with occasional use of a tablesaw on this circuit
  3. 1 15A, 120 V circuit serving all lighting needs both inside and outside the garage along with a future 1/2 HP Garage Door Opener
  4. Both 15 amp circuits ran with 14/2 MC Bx THHN cable
  5. Feeder line ran with 10/3 W.G. from Main Panel to point of exit of main structure, then tied into 10/3 THWN ran within 3/4" metal conduit, buried 18" below the surface and then tied into the sub-panel

I may add a 240 V 2HP 240 V Air compressor at some point, but other than that, the Garage doesn't have any future wiring requirements.

Here's the sub-panel I'm looking at purchasing as of right now:

Main Lug Sub Panel

Will this meet my needs? Would you suggest using a different one?

With the setup described above, I won't need a main disconnect at the sub-panel, correct?

Any Feedback will be welcomed.
 
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Old 05-30-05, 08:02 AM
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Do yourself a favor, run 20 amp circuits in the garage. You'd be foolish not to at this point in time.
 
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Old 05-30-05, 09:02 AM
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I agree with Bob--there's no reason to run any 15-amp circuits.

This is a 6-space/12-breaker panel. Because it has the capacity for more than 6 breakers, some inspectors may require a main disconnect. This can be provided with a back-fed double-pole breaker if the inspector so requires. But if you want, you can just wait until he tells you to, as long as you don't cut the feeder wires too short.

A 30-amp feeder will not allow much room for future expansion, but that's okay if you're comfortable that you have accurately predicted all your future needs.
 
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Old 05-30-05, 10:08 AM
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I agree, absolutely no reason not to run a number 6 or 8 feeder. All around performance will be so much better especially if you add compressor. Personally I wouldnt ever feed a garage with less than a number 6.
 
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Old 05-30-05, 10:33 AM
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Thanks for all the great feedback. I am going to adjust my plans accordingly. In summary, I'm going to make the following changes:
  • Run 2 20 Amp Circuits instead of 2 15 Amp circuits (12/2 instead of 14/2 also)
  • Add a back-fed double-pole breaker to the sub-panel (to avoid issues with the inspection and also to have a line of site to a main disconnect)
  • Run a #6 Feeder instead of a #10 feeder

I don't anticipate ever needing more than 30 Amps into the garage, but a #6 Feeder will allow me to upgrade to 60 Amps if necessary, correct? All I would have to do is switch the 30 Amp Breaker at the Main Panel with a 60 Amp Breaker (assumming my main service can handle the extra load).

Thanks again for all the feedback. Hopefully Planning and Development won't have any issues with my plan and I can get the permit in the next week or two.
 
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Old 05-30-05, 11:29 AM
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As long as you're in an upgrading mood, why not a panel with more than six spaces? The cost difference for more space is small.
 
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Old 05-30-05, 12:19 PM
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As long as you're in an upgrading mood, why not a panel with more than six spaces? The cost difference for more space is small.
Any particular panel that you would recommend?
 
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Old 05-30-05, 03:45 PM
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Any of the panels are fine, what does your house have in it? Its nice to have all the same brand. If you have to buy breakers there is no reason not to but a 50 or 60 in right from the start, same cost. SQD Homeline is very reasonable and you can get a 100A main breaker panel cheap, havnt priced one but I suspect around the 50$ range. You could use a main lug and backfeed a 60 too, either way and the extra spaces are nice in a garage. I often run single outlet circuits, makes it great for running tools and you can be on different circuits with some things that way. A big vaccuum darn near uses the whole capacity of a circuit. I like to run lights on their own, usually 2 circuits, you could use 14 wire for those if you like as it makes it easier to hook up to the fixtures and you are never without lights due to a trip on recepts, also leaves them at full power for tools and they can be worked on without being in the dark. Some good planning really pays off in a garage. If you have spaces in the panel, a Homeline breaker costs 4$ there is not much of a reason to gang up a bunch of stuff on a couple of circuits.
 
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Old 05-31-05, 04:39 PM
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If you have to buy breakers there is no reason not to but a 50 or 60 in right from the start, same cost
I only have 100 Amp service at the main panel. I know for sure that I am safe with a 30 Amp Breaker, but I'm concerned that the Inspector will take issue with running 60 Amp service to the Detached Garage when I only have 100 Amp Service to begin with.

My current calculations comes to a 69 Amp True Electrical Load on the main panel with the New 30 Amp Addition.

Furthermore, my existing main panel is an older Challenger Panel. I'm not too sure where to find circuit breakers for it, but it has an unused 30 Amp breaker, which makes it very convenient to run 30 Amp Service to the Garage Subpanel. For now, I'll use this existing breaker and put in a back fed 60 Amp Breaker in the Sub-Panel.

Any of the panels are fine, what does your house have in it? Its nice to have all the same brand.
Do they still make Challenger Panels/Circuit Breakers?

Finally, 1 grounding rod or 2 at the subpanel?

What are your thoughts?
 
 

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