Compressor circuit conduit question

[K Powers]

Im planning my compressor circuit. It will be about 25ft total length, begining at breaker panel through crawl space and out the block wall in the photo. From there into an air conditioner style disconnect then to the mag starter. My question is how do i transition from romex style wire for the crawl space and through block to wire in flex pvc that i can surface mount on sheet rock for a clean looking install

 

[pattenp]

Can you get the Romex into the stud cavity from in the crawl space and fish the wire up inside the wall to the disconnect box? Otherwise just put a short piece of PVC conduit through the block into a LB conduit body and run PVC up wall to disconnect box. You can put the Romex in the conduit to the disconnect box.

 

[K Powers]

Thanks for the reply, so exit the crawl space and enter the back of the disconnect box then run the romex in flex to starter. Ive read some of the discusions on romex in conduit, is it ok based on how short of run (approx 4 ft in conduit)

 

[K Powers]

Sorry didnt awnser first part yes i can access about 1 ft above the block wall in stud cavity

 

[pattenp]

That's not what I was saying. Romex can be put in conduit but for flex you should use THHN in the flex from the disconnect to the compressor. I was thinking you were placing the disconnect box up the wall from where the romex would be coming out of the block so you would need to use rigid PVC up the wall to the box.

Edit: If you do run the romex through the block you need to use a protective sleeve such as a short piece of PVC.

 

[K Powers]

Ok if i can access sheet rock ill run it right into back of box, if not ill run ridgid up to it. Then the disconnect to starter thhn in flex. Thanks for the info

 

[pattenp]

The compressor you have looks like a beast, so what size circuit are you putting in for it? Make sure the circuit is big enough for the motor size.

 

[K Powers]

Thanks the motor is a hoss. Will run a 50 amp circuit, motor draws 36 so with the 1.25 i went with 50 and will run #6 wire

 

[K Powers]

Thought about 45 but thought 50 would be the best margin

 

[pattenp]

I'm going to guess that the motor data label shows 7.5HP? If so you're good to go with the 50A. Even though you have a listed amp draw of 36A the NEC says to use 40A for 7.5HP, so X 1.25 is 50A on the nose.

 

[K Powers]

Yup its a 7.5. First time i test ran the beast it made what little hair i have stand up

 

[pattenp]

From the disconnect to the starter the THHN can be #8 because @ 75C it's good to 50A. The Romex does need to be #6 because it has a lower temp of 60C and is good to 55A whereas #8 Romex is only good to 40A.

 

[wyliesdiesels]

Man weve sure been getting a lot of compressor questions lately. Must be early christmas presents!

Pattenp: Isnt it nice when people understand code and that they have to use a certain wire size and dont want to cheap out on the hookup?