Metal strapping on a PVC conduit

[JuanC]

I recently had an inspection at a new county i haven't worked at and was told that i cant have metal “pipe hangers” on a pvc conduit (i had my guy use the hangers to give it a bit of offset so it can connect to the disconnect easier) this is my first time running into this problem as I didn’t think it was a problem since the conduit is plastic. The county is Anne Arundel county in Maryland and they still use the 2017 NEC book, if anyone can help me locate what article talks about this issue id greatly appreciate it.

 

[david]

352.10 (D). Wet locations.
The hangers would need protected.

But you didn't say wet locations

 

[infinity]

Technically the metal straps can limit the expansion and contraction of the PVC. Inspectors here typically want to see the PVC straps. Funny thing is the POCO requires the use of metal straps on the pole when installing an underground service. Personally I think that a metal strap like a Minerlac if not over tightened is fine with PVC.

 

[david]

352.30 (A) securely fastened with in 3ft

Your hangers that are supporting the conduit are they also complying with 352.30 (A)?

 

[david]

Technically the metal straps can limit the expansion and contraction of the PVC. Inspectors here typically want to see the PVC straps. Funny thing is the POCO requires the use of metal straps on the pole when installing an underground service. Personally I think that a metal strap like a Minerlac if not over tightened is fine with PVC.

Interesting the hangers on all thread that i have seen would give him the ability to allow snug but not over tight.

Also the all thread would give enough for expansion.

I guess you would have to be careful with unistrut and strapping as well

 

[JuanC]

352.10 (D). Wet locations.
The hangers would need protected.

But you didn't say wet locations

Not a wet location, the straps in question are located in the basement of a climate controlled house. Would the code still apply since the room maintains a certain temperature year round?

 

[david]

Not a wet location, the straps in question are located in the basement of a climate controlled house. Would the code still apply since the room maintains a certain temperature year round?

You need to ask for clarification. As mentioned by post #3 is it expansion or securing that your inspector has concern with.

 

[JuanC]

You need to ask for clarification. As mentioned by post #3 is it expansion or securing that your inspector has concern with.

The inspector wasn’t clear on his concern but i cant imagine it would be expansion and contraction of the pipe since the temperature is about the same year round. I’m just trying to get as much information as possible about this issue so 1 i can see if it applies to my current project and 2 so I’m more knowledgeable in the future when making these decisions.

 

[ptonsparky]

Click straps are about the only nonmetallic ones I’ve used that are worth a didley doo. Worth the money. Install, push your conduit into place and ‘click’, secured and supported.
There are standoffs designed for PVC but I’ve never used them.

 

[DooWop]

There is a clamp that incorporates a rubber cushion and clamp that is used with Unistrut.
Meant as a vibration absorber and also "locks" the pipe to the support. Vibrations can wear thru many pipes in short order
but don't know is that was a concern.

 

[JuanC]

There is a clamp that incorporates a rubber cushion and clamp that is used with Unistrut.
Meant as a vibration absorber and also "locks" the pipe to the support. Vibrations can wear thru many pipes in short order
but don't know is that was a concern.

Vibration shouldn’t be the concern as it is mounted on the concrete wall but thank you for that knowledge!

 

[david]

Vibration shouldn’t be the concern as it is mounted on the concrete wall but thank you for that knowledge!

In your OP you mentioned metal hangers, it's seems in this post you might be talking about metal conduit straps.

Go to 352.10 (D) even in wet locations metal straps would be allowed, it specifically says or protected against corrosion.

I know of nothing in the NEC that would prohibit metal straps

Added: You might have to use straps for rigid metal conduit so they fit pvc conduit

 

[LarryFine]

Juan, do your 'hangers' clamp the PVC against a non-flexible surface, like 1- or 2-hole straps or Minerallac straps or strut do, or do they allow the PVC to move freely like pipe hangers on all-thread?

 

[JuanC]

This is what the inspector has an issue with. (Excuse the work, I have the new guy doing the grunt work at the moment). I’ve used these straps in other county’s and haven’t had a problem with them when other inspectors would inspect my work. I at least want to understand the issue/issues that could be possible when using these straps on pvc pipe. This is located in the basement so I can’t see expansion and contraction of the pipe being an issue as it is climate controlled year round.

 

[LarryFine]

So, a Minerallac and a 1-hole strap. Technically, he's correct, but in this specific case, an elbow is not going to expand enough to overcome the flexibility of a Minerallac. Long straight runs are the main concern.

 

[infinity]

This is what the inspector has an issue with. (Excuse the work, I have the new guy doing the grunt work at the moment). I’ve used these straps in other county’s and haven’t had a problem with them when other inspectors would inspect my work. I at least want to understand the issue/issues that could be possible when using these straps on pvc pipe. This is located in the basement so I can’t see expansion and contraction of the pipe being an issue as it is climate controlled year round.
View attachment 2571917

In a basement? Isn't worth writing the violation.

 

[JuanC]

Ok so in the 2017 NEC it only mentions the concern on of expansion and contraction of pvc pipe with metal straps? When mounting pvc pipe in outdoor conditions it’s best to use plastic straps rather then metal for that sole reason? I’d like to get familiar with this code since it’s my first time hearing of this.

So, a Minerallac and a 1-hole strap. Technically, he's correct, but in this specific case, an elbow is not going to expand enough to overcome the flexibility of a Minerallac. Long straight runs are the main concern.

 

[hbiss]

PVC straps are garbage. Come back in a couple of years and they will be broken. I never use them and never had a complaint from an inspector.

The inspector is probably picking on you because, well, you probably should have done that differently. Looks very DIY.

-Hal

 

[hillbilly1]

I had an engineer balk at mineralac straps on pvc because it contained the GEC. He said it would act as a choke. Don’t know if it was factual or not, but changed it to a one hole, which satisfied him.

 

[JuanC]

PVC straps are garbage. Come back in a couple of years and they will be broken. I never use them and never had a complaint from an inspector.

The inspector is probably picking on you because, well, you probably should have done that differently. Looks very DIY.

-Hal

Thanks for that comment, I don’t usually like plastic straps either for that reason. I’ve been telling the apprentice to take his time and make things look nice but he’s still new.