PVC project

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
We are at the early planning stages of a Dairy project which will essentially start from scratch in each barn. Existing conduit is EMT and after 17 years it is showing the stress of the environment with some of it being supported by the wires in it. We are talking miles of new exposed PVC and hundreds of nonmetallic enclosures.

How well has PVC held up in projects you have done? Is it worth going up a size or changing to Sched 80 for more rigidity or just strap the heck out of it? 120 degree temp change would not be out of the realm of possibility.
 
ptonsparky said:
We are at the early planning stages of a Dairy project which will essentially start from scratch in each barn. Existing conduit is EMT and after 17 years it is showing the stress of the environment with some of it being supported by the wires in it. We are talking miles of new exposed PVC and hundreds of nonmetallic enclosures.

How well has PVC held up in projects you have done? Is it worth going up a size or changing to Sched 80 for more rigidity or just strap the heck out of it? 120 degree temp change would not be out of the realm of possibility.
Click to expand...

If the EMT is not suitable for this particular environment, then PVC will be much worse. Especially with the temperature changes, as PVC expands and contracts a lot more than its metal counterparts.
 
ptonsparky said:
We are at the early planning stages of a Dairy project which will essentially start from scratch in each barn. Existing conduit is EMT and after 17 years it is showing the stress of the environment with some of it being supported by the wires in it. We are talking miles of new exposed PVC and hundreds of nonmetallic enclosures.

How well has PVC held up in projects you have done? Is it worth going up a size or changing to Sched 80 for more rigidity or just strap the heck out of it? 120 degree temp change would not be out of the realm of possibility.
Click to expand...

PVC can last a very long time. IMO the keys will be using at least as many supports as the NEC requires, for instance with 1/2" PVC a support is required every 3'.

Next thing is the supports have to support it but not secure it. The PVC must be able to move in the supports.

Lastly don't be shy with expansion joints, they are not that costly and may keep the job looking better.
 
Carultch said:
If the EMT is not suitable for this particular environment, then PVC will be much worse. Especially with the temperature changes, as PVC expands and contracts a lot more than its metal counterparts.
Click to expand...
Only reason EMT is not suitable is corrosive conditions typically found in such an application. PVC basically corrosion proof but may not be as mechanically sound as EMT.

Other options that have the best of both are typically much more expensive.
 
Carultch said:
If the EMT is not suitable for this particular environment, then PVC will be much worse. Especially with the temperature changes, as PVC expands and contracts a lot more than its metal counterparts.
Click to expand...

Yes, PVC moves and if you install it knowing that life is good. :)

In a past life I vinyl sided a house with an experienced carpenter, the thing he had to remind me of is you hang vinyl siding you do not secure it. The nails go through slots and you don't pound them in tight so that the siding can move. If you don't do that it buckles and looks like junk.

Same applies to PVC.
 
ptonsparky said:
We are at the early planning stages of a Dairy project which will essentially start from scratch in each barn. Existing conduit is EMT and after 17 years it is showing the stress of the environment with some of it being supported by the wires in it. We are talking miles of new exposed PVC and hundreds of nonmetallic enclosures.

How well has PVC held up in projects you have done? Is it worth going up a size or changing to Sched 80 for more rigidity or just strap the heck out of it? 120 degree temp change would not be out of the realm of possibility.
Click to expand...

Which way did you go with this? PVC?

We've wired several dairies now using EMT in the freestall barns, they've all been steel buildings, and haven't had any issues. Even the first ones our shop wired 17 years ago.

I just took a look at a new dairy customer that wants some fans added in their parlor and holding pen. Again, it's a steel building but with poor ventilation and no insulation under the roof sheeting. Condensation and rust is an issue here. Not to mention hot summer days too. Quite a bit different than all the other well ventilated barns we've wired in the past with EMT.

The customer wants pvc but the support requirements at 3' are a nonstarter. While I could bump my runs up to 1.25" to meet the 5' support requirements, that's pretty overkill.

I think I'm going to propose pvc coated MC cable at this point, we've done it in the past and with a 6' support requirement this will let me jump from one z channel to the next and still meet code. I'll stretch a string line across the ceilling where I'm running perpendicular to the building with exposed cable to keep my runs straight.

I've seen mention of fiberglass conduit, but I see the code still has the same support requirements for it as pvc. Bummer.

I'm just curious if you've come up with a better option or found a good way to run pvc and meet the support requirements. I can't think of a good way to do it without either upsizing the conduit or buying narrow strips of(maybe 6" x 120"?) galvanized sheet to use as tracks for the pvc to run on across the ceiling.
 
The dairy barn I do maintenance work at is done all in PVC, and has been in operation for 12 years. Except for the steel screws on the junction box covers, and a few places where insufficient expansion fittings were used, the PVC conduit and boxes are still in excellent shape. Its a steel building but the ceiling has steel roofing, so going parallel with the z channels, the 3ft. support requirement could still be met. My experience with SCH 40 PVC, and out of sunlight, it should last indefinitely if properly supported and expansion fittings correctly installed based on distance and temperature range. I favor PVC in corrosive environments due to price and rigidity.
In agricultural corrosive environments, I make sure the box cover screws are nothing else but stainless.
Don't worry about using -1" SCH 40 conduit, if supported properly, and expansion joints used it works great and will not buckle.
I really like Arlington's Quick Latch hangers for quick, neat install. Some people think they don't allow for expansion on smaller conduits and the conduit will rather buckle, but I've proved it otherwise by putting a mark next to a hanger, then setting up a diesel-fired heater and watching the mark move:cool:.
When using short expansion fittings, be very careful to allow enough room for contraction without having the conduit pop out of the joint. These work well for me in most cases. http://www.cantexinc.com/Products/Utility_Duct/Utility_Duct_Couplings/Expansion_1_Piece.php
If fiberglass enclosures get too expensive, you might want to check out Kraloy Hinged JBoxes. I haven't tried them yet, but they look durable.

For outdoors I use PVC at an absolute minimum as it eventually deteriorates.
 
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