Sub-panel Location

[illus101086]

So I'm going to be installing A 90 amp sub-panel for a 80 gallon air compressor and a welder in the near future and also swap over my workshop lights to the sub-panel as well. I know how to go about doing so for the most part but not sure whether I should install the sub panel next to the main panel out in the back of the house or install the sub panel inside of the garage and if I install the sub panel inside of the garage should i run the conduit from the outside or from the insider through the house. I realize the main difference is going to be cost and labor involved and also appearance. Which is why I’m leaning towards running it through the walls and into the garage. Just not looking forward having to run it through the recessed ceiling and stucco to run the wire.

 

[Zeke]

You're not too clear as to whether your garage is attached or not. If not, then you can have one feeder to there, not lights and welder circuits, etc. And the way I see it since you are asking about running wires, would it be better to run one 4-wire cable or a whole conduit full of wires? I know what I'd do.

Also, if you decide now or later to have more than 6 breakers in the garage, you need a sub panel with its own main breaker.

 

[ddawg16]

You are running conduit no matter what....but if it was me...I'd put the sub in the garage so you're not walking back on forth.

And...

As with any garage project.....things get added. At some point you will add something else. Better to have a short run to a box in the garage than trying to run wire through conduit to your sub next to the main.

 

[illus101086]

You're not too clear as to whether your garage is attached or not. If not, then you can have one feeder to there, not lights and welder circuits, etc. And the way I see it since you are asking about running wires, would it be better to run one 4-wire cable or a whole conduit full of wires? I know what I'd do.

Also, if you decide now or later to have more than 6 breakers in the garage, you need a sub panel with its own main breaker.

Its a attached garage, and decided to put the subpanel in the garage but I'm quite certain wont be adding more 6.

You are running conduit no matter what....but if it was me...I'd put the sub in the garage so you're not walking back on forth.

And...

As with any garage project.....things get added. At some point you will add something else. Better to have a short run to a box in the garage than trying to run wire through conduit to your sub next to the main.

That was exactly my thinking as well. I want to do the wiring in wall and I have a bunch of 2/0 awg thhn wire. Is it against code to run it inside a conduit in a recessed ceiling?

 

[matt_i]

Even with "free" #00 but you need ~90amps total....it seems like some overkill....which is OK, I support that line of thinking ...but running a beastly conduit isn't always a lot of fun.

 

[illus101086]

Even with "free" #00 but you need ~90amps total....it seems like some overkill....which is OK, I support that line of thinking ...but running a beastly conduit isn't always a lot of fun.

It is overkill, but I have a bunch 400ft of 2/0 Thhn service wire and figured id use it for the sub-panel.

 

[Norcal]

It is overkill, but I have a bunch 400ft of 2/0 Thhn service wire and figured id use it for the sub-panel.

Your going to run into issues terminating it.

 

[Jim greengo]

You are running conduit no matter what....but if it was me...I'd put the sub in the garage so you're not walking back on forth.

And...

As with any garage project.....things get added. At some point you will add something else. Better to have a short run to a box in the garage than trying to run wire through conduit to your sub next to the main.

 

[illus101086]

Your going to run into issues terminating it.

Could you please elaborate? I mean i know its gonna be a pain in the *** running this wire just because the size alone.

 

[mm08822]

Could you please elaborate? I mean i know its gonna be a pain in the *** running this wire just because the size alone.

Before you buy any cb’s for your main panel or the new sub-panel itself, make sure the feeder cb’s can handle 2/0. Siemens QP 90-125A cb’s can handle up to 2/0 for example. Check yours. If the sub-panel chosen is a main-lug style, you should be ok as the lugs can usually go pretty large – 300mcm’ish.

Depending on size of feeder cb you choose in the main panel using the 2/0 (assuming AL), you will either need a #6 0r #4 Al egc run with them.

The sub-panel rating could be increased above 100A to 200A to further maximize the value of using the leftover 2/0 for minimal $ increase. The ground bar should handle up to #4 but verify – may need an adapter. Don’t use 2/0 for the egc.

You will need at least 1.5” conduit for the feeder.

 

[illus101086]

Before you buy any cb’s for your main panel or the new sub-panel itself, make sure the feeder cb’s can handle 2/0. Siemens QP 90-125A cb’s can handle up to 2/0 for example. Check yours. If the sub-panel chosen is a main-lug style, you should be ok as the lugs can usually go pretty large – 300mcm’ish.

Depending on size of feeder cb you choose in the main panel using the 2/0 (assuming AL), you will either need a #6 0r #4 Al egc run with them.

The sub-panel rating could be increased above 100A to 200A to further maximize the value of using the leftover 2/0 for minimal $ increase. The ground bar should handle up to #4 but verify – may need an adapter. Don’t use 2/0 for the egc.

You will need at least 1.5” conduit for the feeder.

The main panel is actually a Siemens and i verified the other day that the 90 amp breaker will allow for a 2 awg cable. And the cable im using is Cu not AL
SO i guess ill be going with 6awg for grounding.

 

[mm08822]

The main panel is actually a Siemens and i verified the other day that the 90 amp breaker will allow for a 2 awg cable. And the cable im using is Cu not AL
SO i guess ill be going with 6awg for grounding.

A 90a Siemens QP cb sold today (Q290P) is rated for a max size of 2/0. A #2 conductor will fit in that.

#2 ≠ 2/0. Which do you have?

You have cable (as in a multi-conductor assembly) or an individual conductor?

Since you have 2/0 CU, why bother with a 90a cb? That size cb costs more than 100a. Could also use 125a if you upsize your sub-panel.
If you ocp the feeder at 100A or less need #8 Cu egc. Over that and up to 200a you will need #6 Cu.

 

[illus101086]

My apologies for the confusion but yes I meant 2/0 awg . Also did a remodel addition back in 2004 so everything has been updated or add where needed which is why I went with 125amp 16 circuit 8 space panel because garage has plenty outlets and lighting except for the 240 outlets. Also don’t want to exceed 6 circuits And have to add another main shutoff. But will swap the 90 amp for. 100 amp break for sure


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