I am building a free standing garage/shop on the left side of my house. My main service panel (200A) is surface mounted on the right side of the my house. The house is brick veneer.

I want to install a 150A sub panel in the garage/shop. I will have to come out of the side of the main service panel and up @ 8ft into the eaves. I intend to use 2" PVC here

Go through the eaves and 65ft across the attic to the opposite side of the house. No PVC used here.

Exit the opposite side of the house and go down the side of the house to at least 18" below grade. I will use 2" PVC here

Then 8ft horizontally below grade to the side of the garage. I will use 2" PVC here.

Then up vertically approximately 8ft and into the garage/shop sub panel

The run should be no greater than 120ft. I live in the Austin TX area and the summer temps in the attic can reach 110-115 F. Ambient temp outside can reach 100-105 on occasion.

I am planing on using 2/0 Al SER for the wire. I will be running 220 V tools and welders not all at the same time. The live load at any one time should not exceed 80-90A (round number)

Is the 2/0 wire adequate considering the length of run and potential drop?

Will the PVC cause excessive heat on the wire?

First question I have is how do you plan to get a 150 amp breaker into a 200 amp panel?

Next, #2/0 Al is only good for 135 amps, will need #3/0 Al, which can handle 155 Amps. Using the ambient temp correction factor of .82 for 114-122 DF will allow 127 amps.

The calculated load shall not exceed 80% of the circuit breaker, which is 120 amps, so #3/0 is fine for this feeder running through a high temp area.

Voltage drop is not an issue with this load and distance.

But, how did you calculate the load?

Your not planning on running SER cable through the conduit, are you?

If I read you correctly, I should not plan on using 3/0 SER through PVC, which I was going to do. If I should not do this then what should I use?

I calculated the load by totaling up amp requirements for the tools, lights, appliances etc that would be running at the same time in the Shop. I am currently running all these tools off a 100A sub panel in the main house garage which includes the rest of the house. I am just transferring the existing load from the main house to the shop. I would not be running any major tools at the same time.

I have a cutler hammer main lug load center. It has a 2 pole 150 amp breaker that will fit into it. I went with the 150 A center because it has 32 spaces and circuits. If needed I will drop the center down to 125A with a 125 2 pole breaker

SER cable will not pull through PVC conduit, would need 4 inch.

You will be very disappointed, frustrated, and need to start over, if you did try to pull SER cable through a conduit of any distance.

Underground and where exposed going to the attic need to install a compete conduit system and pull through #3/0 Al XHHW,3 #3/0 and 1 - #4, all aluminum wire with XHHW insulation.

You may change over to SER cable using large junction boxes, but then you would have the connections at both ends of the attic. With the proper fittings, would be better using PVC conduit through the entire circuit.

I ask about how to get 150 amps from a panel, as most load-centers do not have a 150 amp breaker to fit.

Can you provide the model number of your panel, so I can confirm yours can accept a 150 amp breaker?

I was not able to find the model number on the main service panel (it's a cutler hammer). However the data sticker says to use CH, CHAF, CH3, or CHT type breakers. The cutler hammer catalog CH series has a 2 pole 150 AMP breaker. The Elliot Electric Co. catalog number is CH2150.

The electrical store people gave me the same questionable response about pulling SER through PVC that you gave me. After I thought about it I have also come to the same conclusion I will have to use XHHW.

The largest knockout hole I have available is 3 inches. However chart C10 indicates 2" PVC/SCH40 will be sufficient for 3 - #3/0 and 1 - #4 wires.

OK I see that the CH series panels are all rating for 200 amp branch breaker. Not many panels allow that high a rating, but in your case your in good shape.

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/vol01_tab01.pdf


Good that you mentioned you planned to pull SER cable through conduit. You would had been in bad shape if you had installed the conduit, and purchased the cable and tried it.

Thanks for all your help