Critique my plans for garage power

[Jeff590]

I’m hoping you guys can review my plans for getting power to the new garage before I draw it up and submit to the county.

Current status: We are the second owners of our house, and the builder ran wire to the attached single car garage when he built it. My understanding is that he offered a detached 2 car garage as an option, so he did the wiring like that for all his homes. When we moved in, it was not connected to anything, just run from the main 200 amp panel to a small 6x6 box in the garage. Wiring is #2 aluminum (Mobile Home Feeder I guess).

I added an Eaton load center in the garage and put an 80 amp breaker in the main panel. Why 80 amp? Because Home Depot had it in stock and I didn’t need a lot of power to the attached garage. I’m running an 80 gallon air compressor on a 30 amp 220V circuit and added a 20 amp circuit with more 120V outlets and that’s it (lighting, garage door openers, etc. are all handled with dedicated circuits, not off the subpanel). The subpanel is the Eaton “125 Amp 12-Space 24-Circuit Type BR Main Lug Load Center Value Pack” from Home Depot and does not include a main breaker (this one)

So now that the detached garage is done, I want to run a circuit off the Eaton subpanel in the attached garage to the detached garage. Run is about 35 feet. I am planning to run #8 stranded CU THHN wire in conduit to the new garage and put in a subpanel with a disconnect (a 50 amp breaker). New garage load is not huge – lighting (interior and exterior), and a handful of 20amp 120V outlets. No plans for 220V in the new garage, but was going to run heavier wire in case I wanted it in the future.

Now the questions:
1. Do I need a disconnect in the Eaton subpanel in the attached garage? (there are only 2 breakers there now with a plan for the third, but space for 12)
2. I was planning a 50 amp breaker in the Eaton subpanel and another 50 amp as the main in the new garage subpanel – is that correct?

Any other suggestions welcome

 

[wyliesdiesels]

I’m hoping you guys can review my plans for getting power to the new garage before I draw it up and submit to the county.

Current status: We are the second owners of our house, and the builder ran wire to the attached single car garage when he built it. My understanding is that he offered a detached 2 car garage as an option, so he did the wiring like that for all his homes. When we moved in, it was not connected to anything, just run from the main 200 amp panel to a small 6x6 box in the garage. Wiring is #2 aluminum (Mobile Home Feeder I guess).

I added an Eaton load center in the garage and put an 80 amp breaker in the main panel. Why 80 amp? Because Home Depot had it in stock and I didn’t need a lot of power to the attached garage. I’m running an 80 gallon air compressor on a 30 amp 220V circuit and added a 20 amp circuit with more 120V outlets and that’s it (lighting, garage door openers, etc. are all handled with dedicated circuits, not off the subpanel). The subpanel is the Eaton “125 Amp 12-Space 24-Circuit Type BR Main Lug Load Center Value Pack” from Home Depot and does not include a main breaker (this one)

So now that the detached garage is done, I want to run a circuit off the Eaton subpanel in the attached garage to the detached garage. Run is about 35 feet. I am planning to run #8 stranded CU THHN wire in conduit to the new garage and put in a subpanel with a disconnect (a 50 amp breaker). New garage load is not huge – lighting (interior and exterior), and a handful of 20amp 120V outlets. No plans for 220V in the new garage, but was going to run heavier wire in case I wanted it in the future.

Now the questions:
1. Do I need a disconnect in the Eaton subpanel in the attached garage? (there are only 2 breakers there now with a plan for the third, but space for 12)
2. I was planning a 50 amp breaker in the Eaton subpanel and another 50 amp as the main in the new garage subpanel – is that correct?

Any other suggestions welcome

What is the HP rating on the compressor?

Gallons means nothing...

1) no u dont need a disconnect for a panel that is in an attached structure.
2)yes that is fine however, i would go with #2 AL MHF. It will cost you about the same but will give you 40a more ampacity...

 

[Jeff590]

What is the HP rating on the compressor?

Gallons means nothing...

1) no u dont need a disconnect for a panel that is in an attached structure.
2)yes that is fine however, i would go with #2 AL MHF. It will cost you about the same but will give you 40a more ampacity...

I could not find a HP rating on the motor when I looked this morning, but I did see a 12.5A rating. It's older, but from Googling around looking at specs I believe it is a 3HP unit.

So is the MHF direct burial or would you run it in conduit? If I did go use the MHF, what break would you use to feed the detached garage? 80 amp to match the one in the main panel box?

 

[wyliesdiesels]

MHF can be direct buried but conduit is recommended. It needs to be in conduit indoors. Since you were already gonna be using conduit i figured this was a no brainer.

#2 Al MHF can be breakered at 90a max...but since u have 80a for attached subpanel, u could do 80a breaker or upgrade the 80a to a 90a....

Dont forget 2 ground rods and to isolate the neutral bar. U may meed a separate ground bar kit.

12.5a is a little low for 3HP....

 

[Jeff590]

MHF can be direct buried but conduit is recommended. It needs to be in conduit indoors.

So is there another type of similar cable that does not need to be in conduit indoors? The reason I ask is that the run from the main panel box to the attached garage that the builder did is not in conduit and was inspected by the County.

 

[AntonLargiader]

Basically individual conductors need to be in conduit indoors. SER is your typical non-conduit indoor feed cable. That's the gray jacketed stuff. There's also MC (spiral-wrap steel jacket).

 

[wyliesdiesels]

So is there another type of similar cable that does not need to be in conduit indoors? The reason I ask is that the run from the main panel box to the attached garage that the builder did is not in conduit and was inspected by the County.

Take a pic of the cable and post it here

 

[Jeff590]

Here is the cable - just to the right of the bare copper wires.

 

[75gmck25]

From the outside jacket it looks like the Southwire SER cable I bought at Home Depot. My cable is marked on the jacket as TYPE SE CABLE STYLE SER, and also shows that is AL cable with 3 #2 conductors and 1 #4 conductor (2-2-2-4).

Bruce

 

[75gmck25]

From the outside jacket it looks like the Southwire SER cable I bought at Home Depot. My cable is marked on the jacket as TYPE SE CABLE STYLE SER, and also shows that is AL cable with 3 #2 conductors and 1 #4 conductor (2-2-2-4).

Bruce

 

[tyme2par4]

Yes, that's SER Cable. The difference is that all conductors are wrapped in a non-metalic sheath, and the ground conductor is uninsulated.
SER is good above ground and inside with no conduit, but cannot be run underground.
MHF is good anywhere in conduit, or direct burial without conduit (provided it's 2ft down, and you still need conduit where it exits the building, down about a foot and a half).