Question for electricians

[MNBobcat]

Romex inside conduit is not recommended because of the heat that develops inside of the closed space. And also because of water.

THWN or THHN is recommended for inside conduit. We have gophers here so I try and not do direct burial.

 

[Midniteoyl]

URD wire... (Underground Residential Distribution) Aluminum. Does NOT have to be copper OR romex. If you dont wanna do 2-2-4 (or 2-2-2-4), you can do 6-6-6 URD for a little less and you will not have buy larger breakers/boxes than normal. 6-6-6 URD would be equivalent to 8ga copper.

https://www.acehomecenters.net/products/wire-6-6-6-urd-alum-500-|3179017.html

 

[techman]

So what you are saying is that with/without conduit, UF cable is required??? So even single stranded wire would be a no-no unless it is UF (never checked but I doubt what I have on my spools is UF)? I guess it comes down to the insulation on the wire (I've played with that 3 wire underground wire before and didn't like it much...totally encased in molded plastic with the insulated wires inside...a lot of band aids from the knife cuts). So what is different in the wire that the utility uses? That insulation peels off pretty easy.

A USE rated wire is rated for direct burial. No conduit is needed.

paul

 

[aczlan]

So what you are saying is that with/without conduit, UF cable is required??? So even single stranded wire would be a no-no unless it is UF (never checked but I doubt what I have on my spools is UF)?

THWN (Thermoplastic Heat and Water-resistant Nylon-coated) and THHN (Thermoplastic High Heat-resistant Nylon-coated) wires are the type of loose wires that are ok to use in conduit.

Aaron Z

 

[grsthegreat]

So what you are saying is that with/without conduit, UF cable is required??? So even single stranded wire would be a no-no unless it is UF (never checked but I doubt what I have on my spools is UF)? I guess it comes down to the insulation on the wire (I've played with that 3 wire underground wire before and didn't like it much...totally encased in molded plastic with the insulated wires inside...a lot of band aids from the knife cuts). So what is different in the wire that the utility uses? That insulation peels off pretty easy.

no, what im saying is if you use conduit, the only style of romex like wire you can use is UF rated. Regular NMB style romex ( that used in wiring houses) is not allowen in conduit. You can use any individual wire rated for conduit use, suxh as XHHW, THHN, Etc..

Only standard ROMEX is not allowed.

 

[s219]

I'm running XHHW-2 aluminum wire 100' in conduit for a generator install. That happened to be rated for conduit use both underground (wet locations) and inside the home (which has to do with the fire resistance of the insulation, I believe). Some wires are one but not the other.

It's amazing how many different wire insulation types there are, and how many ways they can and can't be used. I almost lost my mind trying to find the right wire type in the right size. Ended up with #1/0 for hots and neutral, and #2 for ground, and less than 2% voltage drop. Technically could have gone with #1 for the neutral but it didn't save much $$.

Be sure to pick a big enough conduit, and also be aware of code regulations for how many wires can be in the conduit (it's based on air space and heat dissipation). I am using 2" PVC and only those four wires can be in there (code would not allow other circuits or future additions). Code would let me use 1-1/2" PVC, but I though it would be a tight squeeze feeding the wire through. In parallel in the same trench, I am running direct bury 12-2 for a battery charger on the generator and a light bulb, and some irrigation control wire for any future control expansions or low-voltage needs (had it laying around). In this case, the voltage drop for 12-2 will be a little higher than I'd like over 100 feet, but it won't matter for the battery charger or light bulb.

 

[techman]

no, what im saying is if you use conduit, the only style of romex like wire you can use is UF rated. Regular NMB style romex ( that used in wiring houses) is not allowen in conduit. You can use any individual wire rated for conduit use, suxh as XHHW, THHN, Etc..

Only standard ROMEX is not allowed.

Romex is a NM listed cable. There is nothing in the code that disallows running it in conduit. If underground, moisture resistant is required, but that does not exclude all romex. NMC is rated for outdoor use and can be used in conduit outdoors.

paul

 

[caver]

Non metallic sheathed cable is what code refers to. Romex is just a trade name from the old Rome Wire Company. For an irrigation timer I would just go with your original plan. Now if you are going to put an outlet in that box "just in case" then up your wire size as was suggested early in the thread.

 

[grsthegreat]

Romex is a NM listed cable. There is nothing in the code that disallows running it in conduit. If underground, moisture resistant is required, but that does not exclude all romex. NMC is rated for outdoor use and can be used in conduit outdoors.

paul

im simply relating it to what the Original question referred to...a 300 foot outdoor, underground run. In this instance, romex (Type NM-B) CANNOT be installed in conduit, as it would require a watertight schedule of wire. I really didnt mean that romex canniot be protected from damage by being installed in Sch 80 PVC conduit, as long as it stays 100% DRY