Conduit Sizing for Romex Wires

[SolarInstaller]

I wanted to ask what is the proper way to size romex wire in PVC conduit?

I have someone that has a detached garage and currently has:
14-3+ground + 10-3+ground run in a 1.25" PVC conduit to his home.

I wanted to see what I would need to upsize the conduit to, if I wanted to add 2-#8 THHN-2 + bare #6 Ground.

Any help would be appreciated. Thank you.

 

[Rock knocker]

Sounds like electrical work goverened by the NEC and would require a licensed electrician, which given the rudimentary nature of this question, you are not.

 

[justsam]

I don't believe you will have a cable fill issue, but I would be concerned about mixing Romex and THHN in the same conduit. I know of no wire fill charts that accommodate this since normally in conduit it would be all THHN, and not a mix. I would also be concerned about trying to pull individual conductors in the conduit and damage the sheath on the existing Romex. I am assuming the PVC you speak of is real electrical conduit as opposed to irrigation.

Another issue that sounds like it is existing are the two feeds to a detached garage. This would be OK for an attached but detached should be a single feed.

What is the voltage that is going to be on the 8ga you are adding? Is this coming off the panels pre or post inverters?

 

[Charles (in GA)]

I wanted to ask what is the proper way to size romex wire in PVC conduit?

I have someone that has a detached garage and currently has:
14-3+ground + 10-3+ground run in a 1.25" PVC conduit to his home.

I wanted to see what I would need to upsize the conduit to, if I wanted to add 2-#8 THHN-2 + bare #6 Ground.

Any help would be appreciated. Thank you.

You are only allowed, by code, one circuit (that is two hots, a neutral, and a ground, which is a 120/240 branch circuit) to a detached building. You are not allowed multiple circuits to a detached building, supplied from another building.

Romex, in conduit or otherwise, cannot be used underground. Conduit of any type, even glued PVC, is considered by the code to be a wet location if underground......... period. You have to use wires with the proper type of markings to show they are water resistant, such as THWN.

Charles

 

[ddawg16]

You are only allowed, by code, one circuit (that is two hots, a neutral, and a ground, which is a 120/240 branch circuit) to a detached building. You are not allowed multiple circuits to a detached building, supplied from another building.

Romex, in conduit or otherwise, cannot be used underground. Conduit of any type, even glued PVC, is considered by the code to be a wet location if underground......... period. You have to use wires with the proper type of markings to show they are water resistant, such as THWN.

Charles

^^^this^^^^

I'm guessing you're using the term 'romex' in a generic sense.

Romex is a brand name to describe sheathed wire...

And while you 'can' run Romex in conduit, it's not normally done. If your running wires in conduit, it's typically stranded wire such as THHN. If it's going to be outside or underground, it has to be for a wet location, hence, THWN.

FYI, most stranded wire now days is marked THHN/THWN.

 

[pattenp]

To size conduit for NM-b (Romex) or UF-b you use the widest cross width to determine the cross section area of the cable to calculate fill limits. Example a flat NM-b cable that is 1/2" wide by 1/4" thick will have its cross section area calculated as if being 1/2" in diameter. Others have commented about NM-b in conduit under ground is a NO-NO. And more than 1 power feed to a detached structure is also a NO-NO.