PVC conduit to PCV nail-on boxes in new construction

[kwired]

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.

In a dwelling it likely is.

I get many people wanting me to run NM in shops and other non dwelling buildings, and first thing is NM generally isn't acceptable by NEC if we don't have at least a 15 minute finish. If it is an accessory building to a dwelling we maybe can get away with NM.

Some of the places I have done like this I have used some ENT if wiring was concealed and found it to go much better then I thought it would, but they often have longer runs between outlets then inside a dwelling would be, and we usually have more then just a single circuit in a run near the panel. I haven't done a thorough cost analysis but seems though it be much closer to cost of NM then compared to running MC cable.

 

[Sierrasparky]

I would think that the owner is looking to fill the walls for thermal mass.
Given that what about the MC cable that is approved for impeded in concrete.

 

[ActionDave]

In a dwelling it likely is.....

What other than this were we talking about?

 

[don_resqcapt19]

...
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.

In the Chicago area, where EMT is required by code for dwelling units, they use the EMT as the EGC, so even less copper.

 

[don_resqcapt19]

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.

Not even EMT costs "gobs and gobs" more.

 

[kwired]

I would think that the owner is looking to fill the walls for thermal mass.
Given that what about the MC cable that is approved for impeded in concrete.

Would work fine. But in OP's case the owner wants the concrete, but doesn't want to spend $$$ on wiring methods rated to be embedded in concrete:roll: Then we got off tangent some on whether or not some methods are that much more expensive.

 

[growler]

Not even EMT costs "gobs and gobs" more.

May not be "gobs and gobs more" but it's still enough to make the average homeowner or GC faint.

 

[growler]

Now it appears that he will be satisfied with romex throughout most of the house, and smurf tube only where he anticipates pulling additional wiring.

what about the MC cable that is approved for impeded in concrete.

Would work fine. But in OP's case the owner wants the concrete, but doesn't want to spend $$$ on wiring methods rated to be embedded in concrete.

That pulling extra wiring is a real kicker. It's hard to plan for conduit fill and de-rateing.

So you plan on maximum use of one of those home runs and the owner want to plan for additional wiring. How's that work out.

 

[fmtjfw]

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??

....

White Book (2013):

ELECTRICAL NONMETALLIC TUBING
(FKHU)
USE AND INSTALLATION
This category covers electrical nonmetallic tubing (ENT) in trade sizes 1/2 to 2 (metric designators 16 to 53) inclusive for installation in accordance with Article 362 of ANSI/NFPA 70, ??National Electrical Code?? (NEC). This tubing is intended for installation and use in accordance with the following information. This tubing can be installed in residential attics up to 3 feet above the bottom of the ceiling joist.
Fittings ? The outside diameters of ENT are such that standard connectors, couplings and outlet boxes for rigid PVC conduit can be employed for ENT that is also constructed of PVC. Installation instructions are provided with each bundle or coil of ENT outlining the procedure to be used when employing cemented-on PVC conduit fittings and outlet boxes. These techniques include the specific cement to be used as well as its application method. Other fittings are covered under Electrical-nonmetallic-tubing Fittings (FKKY).
ENT with mechanical fittings identified for the purpose or with cemented-on fittings is suitable for use in poured concrete.
ENT with cemented-on PVC fittings is suitable for use in:
1. Indoor locations where walls are frequently washed, and
2. Concrete slabs in direct contact with the earth

 

[kwired]

So you plan on maximum use of one of those home runs and the owner want to plan for additional wiring. How's that work out.

If you don't plan for additional wiring, it works about as well as if you ran NM cables and encased them in concrete:happyyes:

White Book (2013):

I was pretty sure they were listed for such use, and even kind of remembered it mentioning using correct cement - but then so does PVC conduit in general. (you are not supposed to use general purpose PVC cement, I will probably go to hell for not using correct cement a few times)

 

[GoldDigger]

If you don't plan for additional wiring, it works about as well as if you ran NM cables and encased them in concrete:happyyes:

I was pretty sure they were listed for such use, and even kind of remembered it mentioning using correct cement - but then so does PVC conduit in general. (you are not supposed to use general purpose PVC cement, I will probably go to hell for not using correct cement a few times)

You can use regular PVC purple primer and PVC cement as long as the can lists conduit as well as pipe as a use. The chemical composition of the PVC is the same as the white schedule 40 except for the color.

Using gray or clear PVC cement which is offered as "electrical" makes for a cleaner looking joint than the common blue fast setting PVC cement, but you have to look harder to make sure you did not forget a joint.

Since the joint will not be under pressure, you may be allowed to skip the primer, but you get a much more durable joint when you use it.

You do not want to use the black ABS cement, it is not the right chemical composition, but you may be able to find a multipurpose cement that will work with all pipe compositions as long as the joint is not under pressure.

PS: I expect I will be seeing you in hell to for wrong cement too.

 

[don_resqcapt19]

May not be "gobs and gobs more" but it's still enough to make the average homeowner or GC faint.

Well it is away of life not that far from me, and the costs, while higher than NM, are not really that much higher. The last city that did a study before adopting an EMT code came up with ~15% increase in the cost of the electrical installation for a typical home built in their area.

I am on the Electrical Commission for my town and while we do not require EMT, in general, for dwelling units, we do it they are over two stories or where ther are more than 6 units in a building. We also require it for any type of commercial occupancy.

About 5 years ago we had an architectural firm appear before us with a request to use MC in an assisted living center, a commercial occupancy under our codes. Our code required EMT for that application. We asked them about the cost differences and they had their contractors re-price the job using EMT. The was a 4.4% cost increase for the use of EMT over the cost of using MC. We did not grant them an exception. The following is from the Electrical Commission"s report to the City Council, recommending that the Council deny the appeal.

The architect told the commission that their estimate of the extra cost is $107,000 out of $2,400,000 for the electrical part of the project. This is 4.4% which is not above the Commission?s expectation and less than 1% of the total project cost.

The commission's expectation was that the cost increase to change from MC to EMT would be ~5%.

 

[pjholguin]

Hello, I have been following this thread and trying to Invision the method that that the GC is going use.
Is his intention to frame a stick house than pour AAC in the voids? If that is what the preferred
method is than NM or UF are NOT permitted per NEC.

Having said that...he has 2 options. 1. Channel voids in the AAC to install wiring.
2. Use the proper material for poured installs.

I think he just needs to bite the bullet and face it, if you want to build using a certain
method. Than he needs to stop comparing wiring methods he cannot use because it's an
apples and oranges comparison. There are cost differences with either way, but you cannot
justify costs differences comparing them. You will drive yourself LOCO.

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]

Hello, I have been following this thread and trying to Invision the method that that the GC is going use.
Is his intention to frame a stick house than pour AAC in the voids? If that is what the preferred
method is than NM or UF are NOT permitted per NEC.

Having said that...he has 2 options. 1. Channel voids in the AAC to install wiring.
2. Use the proper material for poured installs.

I think he just needs to bite the bullet and face it, if you want to build using a certain
method. Than he needs to stop comparing wiring methods he cannot use because it's an
apples and oranges comparison. There are cost differences with either way, but you cannot
justify costs differences comparing them. You will drive yourself LOCO.

And your first option likely costs more then just going to option 2 to begin with. Some people will spend a dollar just so they don't have to spend a quarter sometimes:roll:

 

[pjholguin]

I concur..:happyyes:

And your first option likely costs more then just going to option 2 to begin with. Some people will spend a dollar just so they don't have to spend a quarter sometimes:roll:

 

[SteveGraham]

Thank you all for discussing this project. Here are a couple more details and a bit of clarification:

1- The owner was a contractor (many years ago, now retired) and wants to provide some labor on the job, not only to save money but also to know the details of how the rough plumbing and electrical work is done.

2- He originally wanted the flexibility of conduit for future modification until he heard that it would cost "gobs and gobs more". That's when he said maybe we should just use romex -- without knowing that romex is disallowed in concrete.

3- The proposed house is 1200 square feet, single story, stick framed on a monolithic concrete slab foundation (no wiring in the slab). We will fill the exterior walls with lightweight poured cellular concrete for sound deadening, thermal insulation and fire resistance.

4- Special boxes and connectors add up, thus the reason I originally asked about drilling conduit-size holes in 22 c.i. nail-on boxes. Whether or not this method is approved (the owner will ask the local inspector) he still hopes to minimize materials costs elsewhere.

How would you minimize materials cost on a project like this? Romex everywhere possible (interior walls and attic) then switch to conduit (or smurf tube) (or MC) in exterior concrete filled walls?

 

[kwired]

Thank you all for discussing this project. Here are a couple more details and a bit of clarification:

1- The owner was a contractor (many years ago, now retired) and wants to provide some labor on the job, not only to save money but also to know the details of how the rough plumbing and electrical work is done.

2- He originally wanted the flexibility of conduit for future modification until he heard that it would cost "gobs and gobs more". That's when he said maybe we should just use romex -- without knowing that romex is disallowed in concrete.

3- The proposed house is 1200 square feet, single story, stick framed on a monolithic concrete slab foundation (no wiring in the slab). We will fill the exterior walls with lightweight poured cellular concrete for sound deadening, thermal insulation and fire resistance.

4- Special boxes and connectors add up, thus the reason I originally asked about drilling conduit-size holes in 22 c.i. nail-on boxes. Whether or not this method is approved (the owner will ask the local inspector) he still hopes to minimize materials costs elsewhere.

How would you minimize materials cost on a project like this? Romex everywhere possible (interior walls and attic) then switch to conduit (or smurf tube) (or MC) in exterior concrete filled walls?

Nothing says you have to use same methods for the entire house. Only use raceway methods in exterior walls, and maybe try to minimize to some extent what is in those walls. One way is to place outlets near corner of the room on the interior wall instead of exterior wall if possible. I don't see you increasing the cost significant enough that it will be very noticeable on the total of the electrical installation. If anything the owner will cry more over the cost of AFCI's and GFCI's he ends up needing to pass code.

 

[growler]

Not even EMT costs "gobs and gobs" more.

May not be "gobs and gobs more" but it's still enough to make the average homeowner or GC faint.

Well it is away of life not that far from me, and the costs, while higher than NM, are not really that much higher. The last city did a study before adopting an EMT code came up with ~15% increase in the cost of the electrical installation for a typical home built in their area.

Well, if a City, State or Federal Government did a "Study" that's good enough for me.

 

[readydave8]

Well, if a City, State or Federal Government did a "Study" that's good enough for me.

Like those studies that show how little AfCI'S add to cost of house?

 

[ActionDave]

Not even EMT costs "gobs and gobs" more.

This goes back to Growler's point.

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.

There is a learning curve to overcome when running conduit in a house. Where you live they have had a lot of practice.