Check out some similar questions!

tommybrown · Apr 25, 2008, 11:54 AM

I have a 200amp service panel for my house in Glendale AZ and want to install a 100amp sub-panel for my garage/workshop. The electrical panel is on the other side of the house from the garage and I already have about 15,000 feet of 12ga stranded wire. Is it possible to run a 2 inch conduit through my attic of underground around the house and put about 6 or 7 circuits in it? I know I will lose some amperage when there are a number of wires run in the same conduit but how much I don't know. Additionally, is it permissible to have a 60 amp breaker in my service panel to run power to my 100amp sub-panel? Any help would be great! Thanks

donf · Apr 25, 2008, 12:21 PM

You cannot use #12 AWG to carry 100 amps. #12 gauge conductors are only rated for 20 amps.

Since you did not give a physical length of run, I would suggest you use #2 Copper or #4 Al. as the feeder to your sub panel.

In truth, you need to give us a lot more info.

Washington1 · Apr 25, 2008, 02:16 PM

donf said You cannot use #12 AWG to carry 100 amps.

True, but in this case the OP will be serving the non-service rated panel with a 60A breaker.

Regardless, donf is correct. To add, we do need more information.

donf · Apr 25, 2008, 08:55 PM

"Additionally, is it permissible to have a 60 amp breaker in my service panel to run power to my 100amp sub-panel? Any help would be great! Thanks"

The answer is still no! By code, you cannot use an Over protection device lower than the amount of amperage you are going to carry in the Branch Circuit.

Driving too much current through an current over protection device like a Circuit Breaker, will cause the breaker to trip. Running excess current through a conductor will cause fire.

If you are going to pull 100 Amps off the panel, then you need an over protection device and conductors capable of carrying current.

Also, since you are taking this to a remote subpanel in a different building, you need to ground the subpanel at that remote building. The only way you can use the main panel is to keep the subpanel in the same building.

EPMiller · Apr 26, 2008, 02:41 PM

Originally Posted by donf

"Additionally, is it permissible to have a 60 amp breaker in my service panel to run power to my 100amp sub-panel? Any help would be great! Thanks"

The answer is still no! By code, you cannot use an Over protection device lower than the amount of amperage you are going to carry in the Branch Circuit.

Driving to much current through an current over protection device like a Circuit Breaker, will cause the breaker to trip. Running excess current through a conductor will cause fire.

If you are going to pull 100 Amps off the panel, then you need an over protection device and conductors capable of carrying current.

As I understand it, code does not say that you MAY NOT put a 60A breaker in your main panel, but if you do, the sub panel will only be capable of supplying 60 amps. The size and type of cable connecting the panels and the breaker in the main panel determine what you will be able to get from the sub panel.

Stratmando · Apr 26, 2008, 04:32 PM

You can easily run MANY more than 6 or 7 circuits of #12 through a 2" conduit. Would have to dig up Code Book, but NOT an issue.
A 60 Amp sub panel with #6's ,and #10 for ground.

Washington1 · Apr 26, 2008, 07:41 PM

Additionally, is it permissible to have a 60 amp breaker in my service panel to run power to my 100amp sub-panel? Any help would be great! Thanks

Now you are getting it. Yes, you can do this.

You can install a 60A breaker in your service rated panel to serve your non-service rated panel (Sub-panel). Yet, you cannot terminate a #12 or #10, or combination there of, and use it as feeder from a 60A breaker. You would have to use a # 6 or larger conductor as your feeder to your sub-panel.

tommybrown · Apr 27, 2008, 01:47 PM

Only ANSWER the question on this page here. Do NOT ASK a question.

You are NOT logged in.

tommybrown · Apr 27, 2008, 02:06 PM

OK, here is a little more detail. I live in Arizona and here the service panel is located on the outside of the house. My garage is attached and on the opposide side of my house from the service panel. My plan was to run #1 wire through 2in conduit under ground to feed a 100 amp sub-panel. I bought a bunch of 2in conduit and was planning to buy the wire when I found 3 5000 ft rolls of 12ga stranded wire at a yard sale on the cheap. One black one red and one white. So I changed plans and am now going to put the sub-panel right next to the service panel and run the 12ga wire through the 2in conduit through the attic to the garage. What I need to know is if I can run about 6 or 7 curcuits through the 2in conduit and what I need to do to supply power to the 100 amp service panel that I already have. I am not running anything into the attic that requires anything more than the 12ga wire. Maybe a 220 line for future tools or a welder. Thanks for any help.

donf · Apr 27, 2008, 02:23 PM

Tommy,

What part of NO don't you understand. You can not use a 12AWG conductor to carry 100 Amps. It is flat out not allowed.

Nor can you use a 60 Over protection device to pull 100 Amps from your panel. You can use a 60 Amp Over-protection device with #6 copper to route 60 amps to the garage, providing the run is short enough that you don't have to worry about any voltage drops.

You can use a dual 100 amp breaker with #2 copper to pull 120/240 off the panel and route it to your subpanel for re distribution in the garage.

By the way, the subpanel will have to be in the garage as well.

Stratmando · Apr 27, 2008, 03:18 PM

You can easily run MANY more than 6 or 7 circuits of #12 through a 2" conduit. Would have to dig up Code Book, but NOT an issue. Each would be on a 20 Amp circuit.
A Red and Black can share a Neutral, if they are on opposite phases, and breakers ties together. If you don't want to share neutral, pull 8 whites, 4 reds, and 4 blacks for 8 circuits, plus a #12 for ground. Take Care
You would need #4 copper for 100 Amps, aluminum would be larger.

tommybrown · Apr 27, 2008, 03:34 PM

I am not running 60 amps through 12ga wire. I want to put the sub-panel 4 to 5 feet from the service panel supplying power to the sub-panel with a #1 wire. Then from the sub-panel use the 12ga wire to feed the garage. Thank you Dorf for basically calling me an idiot. I understand I can't run 60 amps with 12 ga wire. Got it. I am simply trying to get you to understand what I need. Appearantly I am failing to do that. I just need to know what breakers and wire size I need to hook up the service panel? Now Dorf, you're saying I need to have the sub-panel in the garage. Why can't it be attached next to the main service panel?

Stratmando · Apr 27, 2008, 04:52 PM

Next to Panel is fine. #1 is Overkill/but fine, I have a habit of that.
Does my 5:18 post make sense?

tommybrown · Apr 27, 2008, 05:02 PM

Stratmando, yes your earlier post makes sense. Would you think pulling a permit would be required?

EPMiller · Apr 27, 2008, 07:23 PM

Originally Posted by tommybrown

<snip>My plan was to run #1 wire through 2in conduit under ground to feed a 100 amp sub-panel. I bought a bunch of 2in conduit and was planning to buy the wire when I found 3 5000 ft rolls of 12ga stranded wire at a yard sale on the cheap. One black one red and one white. So I changed plans and am now going to put the sub-panel right next to the service panel and run the 12ga wire through the 2in conduit through the attic to the garage. What I need to know is if I can run about 6 or 7 curcuits through the 2in conduit and what I need to do to supply power to the 100 amp service panel that I already have. I am not running anything into the attic that requires anything more than the 12ga wire. Maybe a 220 line for future tools or a welder. Thanks for any help.

OK now things are a bit clearer. You want the sub panel right next to the main panel and then you are going to run 6 or 7 20amp circuits from that sub panel, through the conduit to the garage. My work does not use conduit, and I don't have my code book here, so I will have to defer to someone else on the exact count of #12 conductors allowed in a single 2" conduit. It sounds like you will have max 18 or 21 conductors if they are all 120 volt circuits or 240 volt with no neutral. Less if you share the neutral on 2 120 volt circuits on opposite legs (double breaker w/common trip). I believe you will have to have 1 green grounding conductor for each circuit, so you will have to buy that wire.

Stratmando (see above) is correct on your conductors between the main and sub panels, you will need four conductors for that. 2 hot, 1 neutral and 1 grounding. You will have to separate the neutrals and grounds in the sub panel on their own buss bars and the neutral bar must not be bonded to the panel. I question the single #12 ground wire for the seven circuits. However, I repeat, I work with romex, not conduit.

Washington1 · Apr 27, 2008, 08:41 PM

Tommy,

Next time you post with a question, try giving as much information as possible in the beginning. This way we do not have so much confusion!

Thank you!

donf · Apr 28, 2008, 05:02 AM

Tommy,

I believe that the NEC tells us that the subpanel has to be inside the detached garage and it has to be grounded at the garage.

Right now I'm supposed to be in bed now, so I'll check the code on this a little later today.

Meanwhile, if anyone would like to cite the code section that does allow placement of the Sub-panel five feet from the main panel and then a 100' (?) of multiple branch circuits to the detached garage, I'd appreciate it.

Stratmando · Apr 28, 2008, 06:33 AM

When I mentioned NOT issue, The maximimum number of #12 THHN in a 2 " PVC is 98.
Maximum in EMT is 100 #12's. This is 40% fill.
Can't say about a permit in your area.

donf · Apr 28, 2008, 08:42 AM

Strat,

Since you are required to derate current carrying conductors by 75% if there are 3 or more "Currernt Carrying Conductors" within the conduit and Tommy is putting at least 6 or 7 current carrying conductors where are you going to place the derated over protection devices?

Am I missing something here?

It makes no sense to build the subpanel five feet from the SEP.

What does make sense is to pull the 100 amps off the SEP using #4 Copper conductors for the run to the garage wall (Assuming that you LRA allows you to place the sub-panel box on the outside of the structure) then set a Grounding rod for the subpanel and finish the installation.

If he runs it the other way, six or seven cables from the sub-panel (Next to the Main Panel) he has no access to the breakers in the event of an emergency. He's got to leave the garage to run completely around the other side of the house to get to the sub-panel.

Let's all hope there's never an emergency requiring a quick killing of the power to the garage!

Stratmando · Apr 28, 2008, 02:25 PM

Donf,
He may have run out of Breakers is likely why it is 5 foot away.
If the Panel was in the Garage it would be Convient, I am hoping he does not run into a lot of Tripping Breakers. Either way is fine. I am answering his question.
May not be an acceptable place in the Garage or have room? plus he has free #12. This will allow him to do less costly. If he was having Welders, compressors, something requiring other than single pole/20 amps, I may would suggest Sub in Garage.
Take Care