The definitive "what wire for a subpanel" post.

[lawfarm]

I've read 50 different posts on here with 10 different answers on the proper wire to use for a subpanel.

My run is about 50'. I'm using copper. If I go 60 amp, I have to use 4 gauge. Since I never see needing more than 50 amps, I'm going to go 50 amp so I can use 6 gauge copper.

I know separate busses for neutral and ground, ground rod at subpanel, run 4 wires between panels, etc. I know max height for the subpanel. I know that if I run conduit, I have to bury to 18", and if I run direct burial, I have to bury at 24" with conduit risers on both ends. I'm governed by the 2005 NEC where I live.

There is a considerable amount of conflict over what type of wire to run. Some say run SER wire inside conduit. Others say SER isn't specifically permitted by NEC, so it's prohibited. I know that even in conduit, it has to be wire permitted for wet locations. So what's the optimal wire solution here? 6-3 what?

Should I just run 6-3 UF in the conduit (outside) and be done with it? The advantage here seems to be that I would not have to run conduit inside the house; could just route the wire through the joist space.

Or should I pull individual conductors in conduit? (and if so, that would be THNN, correct?) That would mean running conduit for the full length of the run.

 

[Stuart in MN]

That's the fun part about electrical work - there isn't necessarily only one right answer.

UF will work, but it will be a little difficult to pull through conduit, plus you have to make sure the conduit is sized correctly.

THHN/THWN will be easier to install in conduit. You can include a junction box where the conduit comes into the house and transition to NM at that point for indoors.

edited to change from UF to NM...I hadn't had my coffee yet.

 

[manwithtools]

You can include a junction box where the conduit comes into the house and transition to UF at that point for indoors.

Why would you transition to UF inside a structure? Don't you mean NM for inside?

 

[Stuart in MN]

Why would you transition to UF inside a structure? Don't you mean NM for inside?

You're correct - it's early, I haven't had my coffee yet.

 

[pattenp]

The easiest is to run the #6 UF from panel to panel. Do direct bury with conduit raisers. The #6 UF is okay for 55A so technically you can breaker it at 60A. Or do as Stuart suggested using THHN/THWN in conduit outside and NM-b inside.

 

[lawfarm]

Other than the inconvenience of pulling UF in conduit, there's no reason I couldn't just run the full distance in UF (conduit outside, joist space inside) and avoid the inside junction box, right?

 

[manwithtools]

Full distance in UF is fine. It's a ****** to pull and a ****** to strip back to individual conductors at the termination points.

 

[pattenp]

Other than the inconvenience of pulling UF in conduit, there's no reason I couldn't just run the full distance in UF (conduit outside, joist space inside) and avoid the inside junction box, right?

If you read my post, I said you can run the UF from panel to panel. That means no splices needed.

 

[sberry]

I agree, 6 uf panel to panel.

 

[wyliesdiesels]

I've read 50 different posts on here with 10 different answers on the proper wire to use for a subpanel.

Thats because every install is slightly different and there is multiple ways to do it.

My run is about 50'. I'm using copper. If I go 60 amp, I have to use 4 gauge. Since I never see needing more than 50 amps, I'm going to go 50 amp so I can use 6 gauge copper.

Where did you come up with needing #4 for 60a? Maybe youre thinking of aluminum? :dunno

You can use #6 THWN, rated for 65a, for 60a branch feeder...

I know separate busses for neutral and ground, ground rod at subpanel, run 4 wires between panels, etc. I know max height for the subpanel. I know that if I run conduit, I have to bury to 18", and if I run direct burial, I have to bury at 24" with conduit risers on both ends. I'm governed by the 2005 NEC where I live.

You will need 2 ground rods.

And if youre under the 2005 NEC, then you only need 3-wire but i would still do 4-wire for safety reasons.

There is a considerable amount of conflict over what type of wire to run. Some say run SER wire inside conduit. Others say SER isn't specifically permitted by NEC, so it's prohibited. I know that even in conduit, it has to be wire permitted for wet locations. So what's the optimal wire solution here? 6-3 what?

Ive never understood the debate conflict and confusion about SER being prohibited for use underground. But alas, it CANNOT be ran underground.

Should I just run 6-3 UF in the conduit (outside) and be done with it? The advantage here seems to be that I would not have to run conduit inside the house; could just route the wire through the joist space.

Or should I pull individual conductors in conduit? (and if so, that would be THNN, correct?) That would mean running conduit for the full length of the run.

If it were mine, I would use #2 AL MHF in 2" conduit and transition to al SER inside the house.

Using #6 cu with a #10 ground will cost you almost 3 times what MHF costs per foot. $3 vs $1.17

and UF-b is almost $4/ft so....

 

[Vernon29RW]

ground rods are only needed for a detached structure right?

 

[teamextreme]

ground rods are only needed for a detached structure right?

Correct