What size PVC conduit for #6 wire

[jack bacon]

Putting a 50A subpanel in the attached garage so running #6 wire from the basement panel out thru wall above the panel and about 15' to the garage subpanel. What size PVC conduit should I use so I can snake it thru and make the turns where it enters the basement and garage?

Thanks,

Jack

 

[rockwithjason]

1 inch should do nicely assuming that you are pulling 4 wires or less

 

[jlckmj]

I used 1 1/2, the cost difference is minimal and it is still easy enough to work with and put inside the walls if that is what you want to do.

Jim

 

[sands35]

FYI

http://www.jhlarson.com/resources/electrical/sch40-sch80-pvc.html

oversized is good - within reason.

Is the conduit outside or underground? There are riser and damage code requirements that may require schedule 80 (for outside / risers) and cover requirements (for underground).

 

[ddawg16]

1" Works....but it's tight to pull especially if you have a long distance and more than 1 90.

1 1/4" is much more comfortable....and 1 1/2" costs maybe 15% more...but has room for expansion in case you wanted to pull more wires later.

Like garages....it's never big enough.

 

[alfredeneuman]

#8 THWN is rated at 50 Amps. You'd be able to run 3 of them and a #10 ground wire in as small as a 3/4" conduit.

If you already have the #6 THWN wire, then you could increase the breaker size to 60 Amps.

 

[pattenp]

Just what type of wire are you planning to use? You can use #6 NM and may not need conduit if the wire is installed in walls/ceiling and is out of harms way.

 

[Mustang51js]

#8 THWN is rated at 50 Amps. You'd be able to run 3 of them and a #10 ground wire in as small as a 3/4" conduit.

If you already have the #6 THWN wire, then you could increase the breaker size to 60 Amps.

Only issue is #8 max breaker is 40 amps, so he's stuck with using #6

 

[pattenp]

Are you confused? #8 THHN/THWN in conduit can be overcurrent protected at 50A @ 75C. #8 NM is 40A because of being limited to 60C.

Only issue is #8 max breaker is 40 amps, so he's stuck with using #6

 

[Mustang51js]

Are you confused? #8 THHN/THWN in conduit can be overcurrent protected at 50A @ 75C. #8 NM is 40A because of being limited to 60C.

Well then have op do it and see what inspector says. Doesn't matter to me if it fails.

 

[pattenp]

Why would it fail? #8 THHN in conduit at 50A is NEC compliant. Is it your local inspector saying only 40A on all #8?

Well then have op do it and see what inspector says. Doesn't matter to me if it fails.

 

[teamextreme]

Why would it fail? #8 THHN in conduit at 50A is NEC compliant. Is it your local inspector saying only 40A on all #8?

Yes, curious to know where you're coming up with that restriction Mustang. The only overcurrent protection limitations I'm aware of based on wire size are for #14, #12 and #10 called out in the footnote to 310.16, referencing 240.4(D), which limits them to 15a, 20a and 30a respectively. Nothing limiting #8 other than the table itself, which lists either 40a or 50a, depending on the temperature column.

 

[Highbeam]

I had my inspector approve a 50 amp breaker with #8 THWN in conduit to my boiler disco.

 

[Mustang51js]

Why would it fail? #8 THHN in conduit at 50A is NEC compliant. Is it your local inspector saying only 40A on all #8?

Yeah unfortunately around here each town has a different inspector and a lot of them are plumbing inspectors that are allowed to take the test. Each one reads the codes differently so it's tough to keep doing things consistent. So things like keeping 12 wire on 20 amp 10 wire on 30 amp. I just keep things that I know will pass just to make it easier,because they like to fail around here so they have something to do the next week.

 

[Mustang51js]

I've failed a job before because someone put a 100 amp breaker on a 150 amp main breaker panel and didn't use the main built in, I was doing a generator and the transfer switch breaker is rated at 10,000 volts, the main was rated for 20,000 volts. I had to get another inspector and explain that the 150 amp breaker isn't even hooked up. As far as the 40 amp thing I always thought that was the max,guess I will have to look at the temp rating closer.im so used to romex since it's all I really use

 

[tmunsch]

I think the #8 is rated 50 amps free air, not enclosed, and also has to be dual rated THWN/THHN. Check the rating for enclosed in conduit and raceways, I thought it was 40 amps...

T,

 

[pattenp]

NEC 2011 or 2014, look at the heading for table 310.15(B)(16) .... conductors in raceway, cable...

I think the #8 is rated 50 amps free air, not enclosed, and also has to be dual rated THWN/THHN. Check the rating for enclosed in conduit and raceways, I thought it was 40 amps...

T,

 

[mobiledynamics]

? What is the definition of free air. Wire ONLY in Conduit ?

BX/AC is not considered free air right ?

 

[mobiledynamics]

BTW, isn't most if not all THNN is dual rated. I know the stuff I use is dual/triple rated THWN and MTW as well.

For those reading, how come wire you remove let's say from a BX or Romex Shield, you can't use in Conduit. I've yet to google, read and see the ratings of these cables are..

 

[justold]

a conductor will have a max temperature rating . A termination will also have a temp rating , in most cases for residential it is 60 * C . the amp rating for the conductor must be taken from the 60* column .

 

[teamextreme]

? What is the definition of free air. Wire ONLY in Conduit ?

BX/AC is not considered free air right ?

Free air means literally that, it's wire that is NOT in conduit, it is ran through the air, without any conduit, raceway, etc. For most applications, especially those discussed here, free air has very rare applications. We use free air values when sizing conductors in large industrial control panels. They run through the control panel, not in any raceway. Other applications would be wires strung through the air for a overhead service feed for instance, but again that's extremely rare (usually the utility wires are the only ones ran this way). BX/AC would be considered in a conduit.

 

[tmunsch]

NEC 2011 or 2014, look at the heading for table 310.15(B)(16) .... conductors in raceway, cable...

Thanks, I need to do some catching up on my reading....

Free air means literally that, it's wire that is NOT in conduit, it is ran through the air, without any conduit, raceway, etc. For most applications, especially those discussed here, free air has very rare applications. We use free air values when sizing conductors in large industrial control panels. They run through the control panel, not in any raceway. Other applications would be wires strung through the air for a overhead service feed for instance, but again that's extremely rare (usually the utility wires are the only ones ran this way). BX/AC would be considered in a conduit.

Most of our applications are in panelboards and MCC's etc....that was what I was referencing, but I see I need to bone up on my code....

T,

 

[pattenp]

Nope. Breakers are rated as 60/75C so the temp to be used for sizing the wire is based on the wire and device type and installation. You are not just limited to using 60C column for residential, 75C can also be used.

a conductor will have a max temperature rating . A termination will also have a temp rating , in most cases for residential it is 60 * C . the amp rating for the conductor must be taken from the 60* column .

 

[alfredeneuman]

I've failed a job before because someone put a 100 amp breaker on a 150 amp main breaker panel and didn't use the main built in, I was doing a generator and the transfer switch breaker is rated at 10,000 volts, the main was rated for 20,000 volts. I had to get another inspector and explain that the 150 amp breaker isn't even hooked up. As far as the 40 amp thing I always thought that was the max,guess I will have to look at the temp rating closer.im so used to romex since it's all I really use

Replace the word volts with AIC (Amps Interrupting Capacity) and it will make some sense. The AIC rating of a breaker is the maximum current capacity in a dead short condition that the breaker will withstand without damage to the breaker.

 

[TAMPAGT07]

I used 3/4" for a short run, but I would probably use 1 1/2" for a long run....

 

[Norcal]

There are no 20,000 AIC circuit breakers, the next standard rating is 22K. Standard ratings are: 10K, 22K,42K, & 64K, which one being used would depend on the fault current avail., which is not as big a issue for single family homes as it is for non residential services....

To the OP, a little oversize on the conduit will make changes in the future easier. If a electrical contractor was bidding that only the size needed would be used as that would be a way to lose the bid by using a larger size conduit, but since it's not a bid job,, going larger is only a little extra $ in material.

 

[mobiledynamics]

OT, but with MC/AC for example, aside from the paper that generally is wrapped each conductor, the metal is pretty much *around* the overall diameter of the wires inside

With conduit, why is the fill ration generally at the 40% rating ?

 

[alfredeneuman]

from the basement panel out thru wall above the panel and about 15' to the garage subpanel.

It's just 15' of conduit .......
It probably could be pushed without even using a fishtape for such a short run.

 

[Charles (in GA)]

BTW, isn't most if not all THNN is dual rated. I know the stuff I use is dual/triple rated THWN and MTW as well.

For those reading, how come wire you remove let's say from a BX or Romex Shield, you can't use in Conduit. I've yet to google, read and see the ratings of these cables are..

Because the individual conductors inside the Romex or MC are not marked. Pull them out, you will not find any markings on them. Yes, they are THHN rated wire, but the manufacturer did not waste the money to mark them, as they were going into a Romex assembly which was marked. You cannot install the wire if it is unmarked.

This could start another argument about using sections of wire cut from Romex scrap for pigtails in boxes etc.......... but I won't bother to go there, and shouldn't.

Charles

 

[Stuart in MN]

This thread just goes to show there's no subject that can't be beat to death on this board... The question was answered right at the top of the first page.

 

[mobiledynamics]

LOL George. I most definitely guilty of taking a scrap off the floor, stripping the metal off of it ( I live in BX land) and using the shorty as a pigtail if I needed one. It was never even on my radar --- and this is knowing full well, you can't use said conductors in pipe.

 

[Mustang51js]

There are no 20,000 AIC circuit breakers, the next standard rating is 22K. Standard ratings are: 10K, 22K,42K, & 64K, which one being used would depend on the fault current avail., which is not as big a issue for single family homes as it is for non residential services....

To the OP, a little oversize on the conduit will make changes in the future easier. If a electrical contractor was bidding that only the size needed would be used as that would be a way to lose the bid by using a larger size conduit, but since it's not a bid job,, going larger is only a little extra $ in material.

I can't remember what I did yesterday let alone the number on the breaker from 6 months ago lol