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-   -   Detached garage ground wire to house EMT? (http://www.diychatroom.com/f18/detached-garage-ground-wire-house-emt-81359/)

johnd393 09-13-2010 04:31 PM

Detached garage ground wire to house EMT?
 
Can the ground wire going out to the new garage be connected to the conduit in the house instead of running pack to the house panel?

I'm running power from the house to a new detached garage. I was gonna do #2 aluminum for 100 amp, but it has to transverse the whole width of the house before going underground out to the garage. There is some existing 3/4 EMT conduit that can get #6 wire most of the way through the house. 60 amps is probably enough. Three #6 copper fits in the 3/4, and some of it's already in. Some #10 wires for an unused 220v circuit will be pulled out make room for the new #6.
Some of these extra conduit runs and circuits were for a battery/inverter system and generator hookups used by the previous owner. The stuff left with him.

kbsparky 09-13-2010 04:49 PM

If the EMT is properly installed, it qualifies as your "equipment grounding conductor" and no other ground wire is needed. You will have to install a lug in a junction box to change over to a circuit conductor if you don't use metal conduit all the way out.

You should be aware that using #2 Aluminum for a 100 Amp feeder, is not permitted, under the NEC. You'll have to either increase your wire size, or use a 90 Amp breaker.

johnd393 09-13-2010 09:49 PM

Quote:

Originally Posted by kbsparky (Post 500543)
If the EMT is properly installed, it qualifies as your "equipment grounding conductor" and no other ground wire is needed. You will have to install a lug in a junction box to change over to a circuit conductor if you don't use metal conduit all the way out.

You should be aware that using #2 Aluminum for a 100 Amp feeder, is not permitted, under the NEC. You'll have to either increase your wire size, or use a 90 Amp breaker.

Thank you for clearing that up about the EGC
I decided to use #6 copper because most of the EMT is already in the house. I have some #6 on hand. Anything heavier would require about 70ft of new conduit that takes a convoluted route through 3 levels of the house and would require cutting some drywall.

I'm running 1-1/4 plastic pipe underground.

To really do this right all the wires should be a size, or two, larger to reduce voltage drop. The overall one way length from house panel to garage panel is about 207 ft, but it's just a residential garage

goose134 09-13-2010 11:19 PM

Quote:

Originally Posted by johnd393 (Post 500790)
Thank you for clearing that up about the EGC
I decided to use #6 copper because most of the EMT is already in the house. I have some #6 on hand. Anything heavier would require about 70ft of new conduit that takes a convoluted route through 3 levels of the house and would require cutting some drywall.

I'm running 1-1/4 plastic pipe underground.

To really do this right all the wires should be a size, or two, larger to reduce voltage drop. The overall one way length from house panel to garage panel is about 207 ft, but it's just a residential garage


If you're running plastic, you need an EGC.

frenchelectrican 09-13-2010 11:56 PM

Quote:

Originally Posted by johnd393 (Post 500790)
Thank you for clearing that up about the EGC
I decided to use #6 copper because most of the EMT is already in the house. I have some #6 on hand. Anything heavier would require about 70ft of new conduit that takes a convoluted route through 3 levels of the house and would require cutting some drywall.

I'm running 1-1/4 plastic pipe underground.

To really do this right all the wires should be a size, or two, larger to reduce voltage drop. The overall one way length from house panel to garage panel is about 207 ft, but it's just a residential garage


I make it bold and that part you do need EGC so there is no way you can get away from this one so run the whole thing with EGC and ya will be fine.

By the way the 16mm˛ {#6 AWG } if in THHN conductor you can use max of 60 amp breaker but if in SE or NM cable then it will knock down to 50 amp IIRC due the tempture rating .

Merci.
Marc

johnd393 09-14-2010 03:01 AM

I know I need to run a ECG in the plastic pipe outside. EMT serves as the ECG inside the house and up to the point where the wires leave the house to the underground plastic pipe. The question, which was answered by kbsparky, is can I attach the outgoing ECG wire to the ECG EMT in the house rather than running a EGC wire all the way back to the house panel.
Johnd

kbsparky 09-14-2010 05:24 AM

Exactly. Just use a junction box to transition from the EMT to the PVC. Install a grounding lug in that junction box, and attach your EGC there.

If you're using #6 THHN circuit conductors on a 60 Amp breaker, all you need is a #10 ground wire.

One more thing: You will need to install a grounding electrode system at the garage, with a conductor from it connected to the grounding bar in the remote panel. Usually, this means one or more ground rods, or other approved electrode(s) assembly. This is in addition to the #10 minimum required conductor you will install in the PVC conduit.

Stubbie 09-14-2010 07:09 AM

Only thing I will add is to double check that the existing EMT fittings and locknuts are made up tight and secure. Existing emt sometimes will get a loose locknut or fitting that may interfere with a good low impedance fault path.

johnd393 09-14-2010 01:09 PM

Quote:

Originally Posted by Stubbie (Post 500879)
Only thing I will add is to double check that the existing EMT fittings and locknuts are made up tight and secure. Existing emt sometimes will get a loose locknut or fitting that may interfere with a good low impedance fault path.


Definately

frenchelectrican 09-14-2010 06:18 PM

I will post the photo what we are refering to.

http://www.galesburgelectric.com/fil...ge/d_11308.jpg

They do come in few diffrent size and shape so that will give you a idea how we dealt with it.

Merci.
Marc

johnd393 09-21-2010 01:13 PM

I'm almost done burying the 1 1/4" pvc pipe. Along with the 3 #6 & a ground, can I add 3 #14 in the pipe for a 3way light switch?

frenchelectrican 09-21-2010 08:47 PM

Quote:

Originally Posted by johnd393 (Post 504991)
I'm almost done burying the 1 1/4" pvc pipe. Along with the 3 #6 & a ground, can I add 3 #14 in the pipe for a 3way light switch?

If you want a three way light switch you have to bring the power from the garage side that is the only way it will allow per NEC code and do you want the light at the house and garage on the same switch circuit??

Merci.
Marc

secutanudu 09-21-2010 09:25 PM

I am assuming he wants a light in the garage able to be controlled from inside the house as well...so he doesn't have to go outside to turn it off?

Detached buildings can only have one circuit, or 1 MWBC. So how can he do it? Would he have to run a wire back into the house for the inside 3-way switch from the garage subpanel?

By the way, you can legally (in terms of sizing, not your particular application) put 3 #6, 1#10 and 3 #14 wires in 3/4" conduit. I found that out by using this raceway fill calc:

http://www.electrician2.com/calculat...alculator.html

frenchelectrican 09-21-2010 09:36 PM

Quote:

Originally Posted by secutanudu (Post 505260)
I am assuming he wants a light in the garage able to be controlled from inside the house as well...so he doesn't have to go outside to turn it off?

Detached buildings can only have one circuit, or 1 MWBC. So how can he do it? Would he have to run a wire back into the house for the inside 3-way switch from the garage subpanel?

By the way, you can legally (in terms of sizing, not your particular application) put 3 #6, 1#10 and 3 #14 wires in 3/4" conduit. I found that out by using this raceway fill calc:

http://www.electrician2.com/calculat...alculator.html

Secutanudu.,

I should clearify the question to the OP to make them understand little more clear if the OP want to run a three way switch circuit and we are aware the Code only allowed one circuit and what I am getting to is if he have power soruce at the first three way switch at the garage side and go to the house side however the issue is is the OP want the outside luminaries on both garage and the house.

If that the case it may change the way he will have to bring out the conductors.

Merci,
Marc

johnd393 09-22-2010 03:56 PM

The original thought is an outside lamp on the detached garage, supplied from a 15 amp circuit in the detached garage, thru a 3way, with 3 #14s going to another 3way in the house.
There is, however an existing outdoor lamp on attached garage with 3way switches. It might be a convenience to put the attached and detached outside lights on the same 3way switches. One 3way would be replaced with a 4way and a 3way in the detached gar. Now this would be supplied from the house end.
My concern is really whether the extra conductors, in the pipe, for the switch would require derating the #6 feed below 60 amps.


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