PVC conduit to PCV nail-on boxes in new construction

[SteveGraham]

I'm a contractor, working for a client who has asked me to use PVC conduit in the walls of his new house. I normally use romex so this is somewhat new to me. In terms of connecting the conduit to typical 22 c.i. PVC nail-on outlet boxes, can I drill holes in the box sides then slide the ends of the conduit into them?

I'm not sure if this makes any difference but I thought I should mention it: After the rough plumbing and electrical is done, the wall cavities will be poured full of aerated concrete thus sealing any gaps between the conduit and boxes and anchoring everything in position permanently.

 

[kwired]

I'm a contractor, working for a client who has asked me to use PVC conduit in the walls of his new house. I normally use romex so this is somewhat new to me. In terms of connecting the conduit to typical 22 c.i. PVC nail-on outlet boxes, can I drill holes in the box sides then slide the ends of the conduit into them?

I'm not sure if this makes any difference but I thought I should mention it: After the rough plumbing and electrical is done, the wall cavities will be poured full of aerated concrete thus sealing any gaps between the conduit and boxes and anchoring everything in position permanently.

Only thing I can think of that may be a NEC violation would possibly be 110.3(B).

Why not use NM 4x4 boxes and mud rings? would likely be easier to work in when it is time to pull conductors.

 

[ActionDave]

I think you would be a whole lot better off using mason boxes or 1900 boxes and mud rings.

One this is for sure, this house is going to cost a whole lot more than one where you can use romex....lots more....gobs and gobs more....I hope not more than you or the owner thinks.

Welcome to the forum.

 

[kwired]

I think you would be a whole lot better off using mason boxes or 1900 boxes and mud rings.

One this is for sure, this house is going to cost a whole lot more than one where you can use romex....lots more....gobs and gobs more....I hope not more than you or the owner thinks.

Welcome to the forum.

Which is why we must save a little by using the nail on boxes:happyyes:

 

[iwire]

I'm a contractor, working for a client who has asked me to use PVC conduit in the walls of his new house. I normally use romex so this is somewhat new to me. In terms of connecting the conduit to typical 22 c.i. PVC nail-on outlet boxes, can I drill holes in the box sides then slide the ends of the conduit into them?

I'm not sure if this makes any difference but I thought I should mention it: After the rough plumbing and electrical is done, the wall cavities will be poured full of aerated concrete thus sealing any gaps between the conduit and boxes and anchoring everything in position permanently.

Forget using regular single gang outlet boxes, besides the potential issue of being called on a listing violation there is the issue of them being too small to bring two or more conduits into one end. There will be times you need to enter at least two conduits at one end.

If you enter the side you will also have a hard time putting devices in, larger devices like GFCIs might not fit at all.

I would use 4" x 4" plastic boxes that have KOs for pipe not cable clamps. On top of that box use plastic single and double gang plaster rings. Remember to use 5/8" raised rings for 1/2" sheet rock and 3/4" raised rings for 5/8" sheet rock.

I might see if the owner would be happy with 'smurf tube'

If you stick with PVC use a lot of 3/4" as you really can't pull many conductors in 1/2" PVC. There is less space inside 1/2" PVC than there is in 1/2" EMT due to the wall thickness of PVC.

 

[SteveGraham]

The owner had a shocking reaction to this comment:

This house is going to cost a whole lot more than one where you can use romex....lots more....gobs and gobs more

Now it appears that he will be satisfied with romex throughout most of the house, and smurf tube only where he anticipates pull additional wiring. Thank you all for the helpful thoughts and suggestions.

 

[kwired]

The owner had a shocking reaction to this comment:



Now it appears that he will be satisfied with romex throughout most of the house, and smurf tube only where he anticipates pull additional wiring. Thank you all for the helpful thoughts and suggestions.

Well then he won't be happy when he finds out NM cable can't be "Embeded in poured cement, concrete, or aggregate" either.

If he wants to fill these walls with concrete, then he will need to use wiring methods in those walls that can be embedded in concrete.

 

[SteveGraham]

Well then he won't be happy when he finds out NM cable can't be "Embeded in poured cement, concrete, or aggregate" either.

If he wants to fill these walls with concrete, then he will need to use wiring methods in those walls that can be embedded in concrete.

I'll tell him. Smurf tube is good for concrete, correct?

Hopefully he will give up the poured concrete insulation approach so I can use romex as usual. Thanks kwired.

 

[kwired]

I'll tell him. Smurf tube is good for concrete, correct?

Hopefully he will give up the poured concrete insulation approach so I can use romex as usual. Thanks kwired.

That is the problem many people have is they hear about some product or way of doing things and hear about the benefits and think they have got to have it. They later find out it may come with other unexpected issues - like making plumbing, HVAC or wiring changes necessary, and then they cry about how much those portions of the job are going to cost.

Reality is I don't think it will cost all that much more to run smurf tube then it will cost to run NM cable. Some situations it may even cost less then NM cable - others it will cost more, but overall I bet it comes out close to the same in most instances.

ENT may seem like it may be a little more costly, but if you have multiple circuits in a run you only need 1 EGC so you will cut back on copper vs NM cable with a EGC in every cable, it installs about as easily as NM cable does so there is only one run instead of multiple runs to make in some situations.

 

[ActionDave]

I agree about the next big idea that involves non traditional methods usually unmentioned drawbacks.

I respectfully disagree. Even using smurf it will cost more than romex. Maybe just just gobs more instead of gobs and gobs. More expensive no doubt.

 

[Little Bill]

I agree about the next big idea that involves non traditional methods usually unmentioned drawbacks.

I respectfully disagree. Even using smurf it will cost more than romex. Maybe just just gobs more instead of gobs and gobs. More expensive no doubt.

In my experience, the fittings for the smurf tube are the most costly part.

 

[growler]

Reality is I don't think it will cost all that much more to run smurf tube then it will cost to run NM cable. Some situations it may even cost less then NM cable - others it will cost more, but overall I bet it comes out close to the same in most instances.

I respectfully disagree. Even using smurf it will cost more than romex. Maybe just just gobs more instead of gobs and gobs. More expensive no doubt.

Both materials and labor will cost more with smurf tubing.

For one thing most residential electricians have never used smurf and if you use commercial electricians most of them have never wired a house. So you take a job that's pretty much paint by the numbers and turn it into something complicated.

 

[mjf]

Both materials and labor will cost more with smurf tubing.

For one thing most residential electricians have never used smurf and if you use commercial electricians most of them have never wired a house. So you take a job that's pretty much paint by the numbers and turn it into something complicated.

:thumbsup::thumbsup:

 

[ActionDave]

Both materials and labor will cost more with smurf tubing.

For one thing most residential electricians have never used smurf and if you use commercial electricians most of them have never wired a house. So you take a job that's pretty much paint by the numbers and turn it into something complicated.

I just re-read my full post, which I submitted without previewing (some very cute girls were chiding on me about going to the carnival that is in town), ugh! Thanks for arranging things so it made sense.

To further the point.... I have done custom homes and commercial. Romex is faster that conduit, any kind of conduit, any day of the week. If the owner is willing to pay for the difference do what he says.

 

[growler]

To further the point.... I have done custom homes and commercial. Romex is faster that conduit, any kind of conduit, any day of the week. If the owner is willing to pay for the difference do what he says.

Dave I wasn't trying to suggest that you don't have expereince with residential and commercial. From the comments of the OP I would think that he is not overly familiar with conduit useage and this is not uncommon for the average residential electrician.

I have had to follow some of the guys that don't really understand how to run smurf and it's not easy (pulling wire). Some forget that it's still conduit and only allows 360 degrees of bend between pull points.

 

[kwired]

I agree with some of what has been said. ENT fittings are expensive.

PVC fittings are not expensive, and may or may not be listed for use with ENT, but sure do work great if not going to be rejected. If they are not listed for such use why do they make them fit so well??

I do agree that "residential" only electricians seem to have some kind of issue with any raceway wiring method - even a short nipple between a panelboard and receptacle seems to be taboo. Some of us that don't limit ourselves to any one particular installation type may not be as efficient at some types but seem to manage to take advantage the ability to work with multiple wiring method types, and will work with what the situation calls for. I have started to use less 8-2, 8-3, 6-2, 6-3 NM cable. got tired of having multiple pieces only 10 or 15 feet long left over that you can never seem to get rid of. Don't use enough of the stuff to make worth buying larger reels either. I do use enough 8 and 6 AWG THHN/THWN that why not run raceway in some of those jobs that I used to use NM cable for?

Can I do a bedroom on the far corner of a house cheaper in ENT then I can with NM cable? Likely not. Can I do a kitchen SABC's with multiple circuits in ENT for less then I can in NM cable - the chances are better then they are with the bedroom. If anything the cost is closer to the same with either method.


Did a finish of a basement more recently, ceilings were to be suspended ceilings, all I did was run NM cable around rooms and stub to some "distribution points" in the ceiling. This went fast and allowed for drywall installation to be done. Came back later and ran EMT for home runs, just needed to make sure to do it before ceiling was done or it will not go quite as easily. I'm confident in my ability to run EMT across the bottom of floor joists much faster then I can drill floor joists and pull NM cables through them. Maybe if I had multiple reels of NM cable and pulled some of the longer runs all at same time this could make some difference, but then I have higher overhead of materials to keep on hand as well. This house had a kitchen added in the basement in the far corner from where electric panel was located. One 3/4 EMT easily took care of the range, SABC's, and a couple other circuits ran to that farther end of the house, and IMO went faster and used less copper then NM cable would have taken.

If you are not convinced this was the better way to go that is fine, we are all different and have different abilities, this is what worked for me.

 

[growler]

I have started to use less 8-2, 8-3, 6-2, 6-3 NM cable. got tired of having multiple pieces only 10 or 15 feet long left over that you can never seem to get rid of. Don't use enough of the stuff to make worth buying larger reels either. I do use enough 8 and 6 AWG THHN/THWN that why not run raceway in some of those jobs that I used to use NM cable for?
Did a finish of a basement more recently, ceilings were to be suspended ceiling, all I did was run NM cable around rooms and stub to some "distribution points" in the ceiling. This went fast and allowed for drywall installation to be done. Came back later and ran EMT for home runs, just needed to make sure to do it before ceiling was done or it will not go quite as easily. I'm confident in my ability to run EMT across the bottom of floor joist much faster then I can drill floor joists and pull NM cables through them.

If you are not convinced this was the better way to go that is fine, we are all different and have different abilities, this is what worked for me.

Look at that basement job with a normal sheetrock ceiling and see which would have been easier.

Finding a place where it may make sense to run conduit and may have worked out well for you isn't the same as saying that running conduit and NM are around the same cost because they are not.

The OP is going to have more labor in a house roughed in Smurf than if he were allowed to use NM and there is no way around it.


If he's lucky and they put a suspended ceiling in the basement that may help somewhat but that hasn't been mentioned. It may be a two story house built on a slab ( we don't know ). There really are not as many basements down there ( water level not far down ).

 

[kwired]

Look at that basement job with a normal sheetrock ceiling and see which would have been easier.

Finding a place where it may make sense to run conduit and may have worked out well for you isn't the same as saying that running conduit and NM are around the same cost because they are not.

The OP is going to have more labor in a house roughed in Smurf than if he were allowed to use NM and there is no way around it.


If he's lucky and they put a suspended ceiling in the basement that may help somewhat but that hasn't been mentioned. It may be a two story house built on a slab ( we don't know ). There really are not as many basements down there ( water level not far down ).

The OP is going to have more labor if he roughs in with NM cable then the inspector tells him it can't be embedded in concrete:happyyes:

I never said it would be cheaper to do the entire house with ENT, I said it can possibly be cheaper or at least about the same for certain portions or specific places. Get on the far end of the house from the service panel and have just one or two bedroom circuits in that area of the house and it will almost definitely be cheaper to use NM cable for "roping" the room(s). A long home run of multiple circuits may or may not be cheaper to use raceway methods. ENT is not all that great for long runs if not well supported, it tries to move when pulling conductors and can give troubles, people not used to running it will not know this and will forever curse it after having that happen. Long straight portions of runs is maybe better to use regular PVC conduit instead.

Running several NM cables where foam insulation will be applied or holes will be filled with it, can take extra labor in drilling extra holes and providing extra support and separation between cables, but rules for a raceway don't really change just because you will be using spray foam insulation, you can't disregard this fact either. You do have to consider cost of copper, cost of labor and cost of accessories not just how much per foot a raw cable costs vs how much per foot a raw raceway with same size and number of conductors inside costs. One could make home runs of 12-2 w gnd and use 8 cables with 16 conductors and 8 EGC's for a certain distance. Or one could use a single run of raceway, run MWBC's (AFCI requirements have taken a little bit of practicality out of this option, but maybe if we are running NM cable in a non dwelling.... which is possible, and no AFCI is required....) and still run 8 circuits using only 12 conductors plus one EGC (or use a metal raceway and no separate EGC) for the same group of home runs. Copper is high enough priced that it may be worth consideration, you would cut back on 7 EGC's in my example here. Now if the run needs a lot of bending and piecing it is probably not worth the labor, but if it is a simple enough run it very well may be less total cost then using NM cables.

 

[ActionDave]

Dave I wasn't trying to suggest that you don't have expereince with residential and commercial. From the comments of the OP I would think that he is not overly familiar with conduit useage and this is not uncommon for the average residential electrician.....

I did not think you were questioning my ability. I agree with you completely. I just wanted to add that even for someone who is familiar with commercial methods it will still be difficult and more costly.

Finding a place where it may make sense to run conduit and may have worked out well for you isn't the same as saying that running conduit and NM are around the same cost because they are not.

Exactly. I have used conduit to my advantage with good results.

The OP is going to have more labor in a house roughed in Smurf than if he were allowed to use NM and there is no way around it... .

Did a whole house in conduit and MC once. I knew it would be more labour but was very surprised how long it took. Thank heaven above it was T&M.

 

[ActionDave]

The OP is going to have more labor if he roughs in with NM cable then the inspector tells him it can't be embedded in concrete:happyyes:

I never said it would be cheaper to do the entire house with ENT, I said it can possibly be cheaper or at least about the same for certain portions or specific places. Get on the far end of the house from the service panel and have just one or two bedroom circuits in that area of the house and it will almost definitely be cheaper to use NM cable for "roping" the room(s). A long home run of multiple circuits may or may not be cheaper to use raceway methods. ENT is not all that great for long runs if not well supported, it tries to move when pulling conductors and can give troubles, people not used to running it will not know this and will forever curse it after having that happen. Long straight portions of runs is maybe better to use regular PVC conduit instead.

Running several NM cables where foam insulation will be applied or holes will be filled with it, can take extra labor in drilling extra holes and providing extra support and separation between cables, but rules for a raceway don't really change just because you will be using spray foam insulation, you can't disregard this fact either. You do have to consider cost of copper, cost of labor and cost of accessories not just how much per foot a raw cable costs vs how much per foot a raw raceway with same size and number of conductors inside costs. One could make home runs of 12-2 w gnd and use 8 cables with 16 conductors and 8 EGC's for a certain distance. Or one could use a single run of raceway, run MWBC's (AFCI requirements have taken a little bit of practicality out of this option, but maybe if we are running NM cable in a non dwelling.... which is possible, and no AFCI is required....) and still run 8 circuits using only 12 conductors plus one EGC (or use a metal raceway and no separate EGC) for the same group of home runs. Copper is high enough priced that it may be worth consideration, you would cut back on 7 EGC's in my example here. Now if the run needs a lot of bending and piecing it is probably not worth the labor, but if it is a simple enough run it very well may be less total cost then using NM cables.

Take every one of the advantages of conduit you have listed I still maintain that romex is cheaper than any conduit any day of the week.