Adding Circuits to Garage - Grounding EMT

[MNiceGuy]

I am about to install a pair of 20A circuits in my garage. Each with terminate to a single device; one down line of the other.

I will be using EMT and steel wall boxes. For the first 20ft of the run, the EMT will contain both sets of conductors as well as a single ECG. All wire is 12AWG.

I understand that per NEC, I can use the EMT itself as the equipment ground but I'd prefer to err on the side of caution and will be pulling an EGC in the bundle.

QUESTIONS:

• Can someone confirm that I can use this single 12AWG EGC for both circuits?
• If the above is correct, do I bond each of the two boxes (again, on separate circuits), directly to the EGC by way of the grounding screw?

 

[Shiftless]

Yes to both.
Let’s wait for a pro to confirm but I hope it is correct because that’s the way I did it in my garage.

 

[Terry D]

You can share that #12 egc between the two circuits. You will need a pigtail to the box and devices. All the grounds get tied together

 

[dscheidt]

I am about to install a pair of 20A circuits in my garage. Each with terminate to a single device; one down line of the other.

I will be using EMT and steel wall boxes. For the first 20ft of the run, the EMT will contain both sets of conductors as well as a single ECG. All wire is 12AWG.

I understand that per NEC, I can use the EMT itself as the equipment ground but I'd prefer to err on the side of caution and will be pulling an EGC in the bundle.

QUESTIONS:

• Can someone confirm that I can use this single 12AWG EGC for both circuits?
• If the above is correct, do I bond each of the two boxes (again, on separate circuits), directly to the EGC by way of the grounding screw?

In general, when pulling a ground through conduit, you only need a single EGC, sized for the largest circuit in the conduit. With metal conduit, you ground each box (and device, if it's not a self-grounding device. A self grounding device has a spring that holds one of the attachment screws in, so it's ground through the box as long as the screw is installed into the box. yOu can run a wire, too, if you want.)

 

[BreeStephany]

Size your grounding conductor on the size of the largest circuit in the conduit and base the size off of NEC 250.122. You only need 1 grounding conductor in the conduit. Use a grounding pigtail at every box to bond the box and conduit to the grounding system and then pigtail off of the intersection of the box pigtail and your grounding conductor to use to ground your devices.

Based on NEC 250.122, if you are using 20A circuits at both locations, you just need a single #12 THHN green grounding conductor in the conduit between boxes and a single #12 THHN green grounding conductor from your first box back to your panel.