Detached Garage 100 amp panel

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1793

1793

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Location
Louisville, Kentucky
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Inspector
I'm getting ready to run an underground feed out to a detached garage. The new panel is a 12/24 100 amp MB.

Looking for confirmation on this one, under 2008, from the main service also 100 amp, in the basement I need to use a 1/0 SER (AL). Correct?

I will be Channing over to PVC and I was thinking of using #1 (AL) or do I need to stay with the 1/0?

Any other thoughts?
 
1793 said:
I'm getting ready to run an underground feed out to a detached garage. The new panel is a 12/24 100 amp MB.

Looking for confirmation on this one, under 2008, from the main service also 100 amp, in the basement I need to use a 1/0 SER (AL). Correct?

I will be Channing over to PVC and I was thinking of using #1 (AL) or do I need to stay with the 1/0?

Any other thoughts?
Click to expand...

Why cut it and add splices in ? why not just go 1/0 ser the whole way and sleeve the end of the run.
 
acrwc10 said:
Why cut it and add splices in ? why not just go 1/0 ser the whole way and sleeve the end of the run.
Click to expand...

SER isn't permitted in underground raceways. 338.12(A)(2).
 
100 amp URD or #2 copper is what I would run unless you can go above ground in conduit then I would use the SER.
 
1793 said:
I'm getting ready to run an underground feed out to a detached garage. The new panel is a 12/24 100 amp MB.

Looking for confirmation on this one, under 2008, from the main service also 100 amp, in the basement I need to use a 1/0 SER (AL). Correct?

I will be Channing over to PVC and I was thinking of using #1 (AL) or do I need to stay with the 1/0?

Any other thoughts?
Click to expand...


#1 Aluminum is all you need. If the house has 100 amp service why would you run 100 amps to the garage?
 
Dennis Alwon said:
#1 Aluminum is all you need. If the house has 100 amp service why would you run 100 amps to the garage?
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Customer is adding a welder (50 amp) and other shop equipment and does not want to fall short in the garage.
 
1793 said:
I'm getting ready to run an underground feed out to a detached garage. The new panel is a 12/24 100 amp MB.

Looking for confirmation on this one, under 2008, from the main service also 100 amp, in the basement I need to use a 1/0 SER (AL). Correct?

I will be Channing over to PVC and I was thinking of using #1 (AL) or do I need to stay with the 1/0?

Any other thoughts?
Click to expand...

How far are you going with this run? Don't forget to take voltage drop into consideration.

I also question the placement of a 100 amp sub on a 100 amp service. You may be overloading the service. What if the custormer is cooking Thanksgiving dinner with lots of electrical stuff on to entertain the visitors and they decide to show their new 50 amp welder off to their cousin? Something has to go! It won't be the 100 amp breaker in the garage, it will be the main in the house.

Your customer strikes an arc, a loud snapping noise ensues and now everyone is in the dark and asking who designed the electrical system.

Really, is it worth that sort of risk?
 
infinity said:
SER isn't permitted in underground raceways. 338.12(A)(2).
Click to expand...

Well I'm glad I know that now.:smile: It's right there in the book" Don't do it."
We don't use much ser out here in CA.
 
I do these all the time and what you need is 2/2/2/4 USE 2 alum mobile home feeder. The 2 suffix makes it suitable for 100 amp underground service. You only need pvc conduit 18" before it leaves the ground and above the ground. It has to be terminated no more than 6 ft after leaving the ground into a panel or j box that changes to another type of conductor. It can be changed to SER in the j box. It doesnt cost as much to run the 100 amp alum as it would 60 amp copper. I doubt the welder pulls over 30 amp unless its a big one. I would put a 60 a breaker in the main panel to make sure your "friend" doesnt load up his 100 a panel
 
1793 said:
I'm getting ready to run an underground feed out to a detached garage. The new panel is a 12/24 100 amp MB.

Looking for confirmation on this one, under 2008, from the main service also 100 amp, in the basement I need to use a 1/0 SER (AL). Correct?

I will be Channing over to PVC and I was thinking of using #1 (AL) or do I need to stay with the 1/0?

Any other thoughts?
Click to expand...

If your going to use a 100A feeder circuit breaker you?ll need at least #1 AL XHHW or THWN according to Tables 310.16 & 13.

I guess you may be able to use Table 310.15(B)(6) if this is considered a ?dwelling unit? if so #2 AL XHHW or THWN can be used, but these conductors "shall not be required to be larger than their service-entrance conductors."

You will also need to include a #6 EGC and earth ground the garage as well without bonding the neutral at the garage sub panel.

I would just let the customer know you are feeding their desired load based on the information they have supplied you. If the service disconnet circuit breaker trips from overloading this action will indicate a need to upgrade to a 200A service disconnect. Of course the best option is load calc. their new garage along with the house and advise accordingly. :)
 
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