EMT vs. PVC in a seaside environment.

[c_picard]

What are your thoughts on the use of EMT in a salt-air type environment? An example would be Cape Cod, or Long Island, where you are never very far from the coast.
I am conduction a phone poll of local AHJ's in these areas, and wanted to check in witht he experts here as well!

The context: Conduit runs on the exterior of residential homes for PV systems.

I am a fan of PVC in these locations, but recognize that with the idea of a "corrosive environment" it's tough to pin down specifics, and is up for some interpretation.

 

[peter d]

PVC, hands down. I would never use EMT anywhere outdoors in this area, and especially not by the ocean. The EMT I do see installed outdoors usually begins to rust within a few years.

 

[buzzbar]

I agree, PVC is the only way to go. EMT will start rusting away as you drive away from the job. You COULD paint the EMT, but who wants to do that?

Also, make sure the straps are either plastic or SS, and all the screws NEED to be stainless steel.

We do a lot of marina work, and in the early days, we would use standard metal straps and screws. Re-visiting past jobs has been an eye opener because all of the screws and straps are disintegrating. It's kind of embarrassing after the fact.

 

[buzzbar]

I forgot to mention that here is Washington state, they actually REQUIRE 'non-corrosive' material to be used in article 555.

 

[c_picard]

The feedback I am getting from the 3rd party wiring inspectors on Long Island is that they have to approve both EMT and PVC by code.

However, I have seen even meter cans paper thin out by the beaches. Like I said, i'm a fan of PVC, but understand the argument that when installed on a roof, even if elevated, it sees extreme UV and temp conditions.
There is also room for human error in the calcs needed to install PVC properly given the crazy temperature swings we see in the Northeast. (we had a hurricane and a blizzard back to back).

555 has some relevant info, thanks for that, and I wonder what type of experience you might have with marine grade coatings? that has been brought up in our discussions as a possible way to extend the life of the EMT.

 

[peter d]

The feedback I am getting from the 3rd party wiring inspectors on Long Island is that they have to approve both EMT and PVC by code.

However, I have seen even meter cans paper thin out by the beaches. Like I said, i'm a fan of PVC, but understand the argument that when installed on a roof, even if elevated, it sees extreme UV and temp conditions.
There is also room for human error in the calcs needed to install PVC properly given the crazy temperature swings we see in the Northeast. (we had a hurricane and a blizzard back to back).

555 has some relevant info, thanks for that, and I wonder what type of experience you might have with marine grade coatings? that has been brought up in our discussions as a possible way to extend the life of the EMT.

Again, I see and use PVC in 99.99% of coastal and marina applications. EMT is code legal but it's just a poor choice.

"RI/MA/LA/CA/NJ/NY" You have quite the coverage area.

 

[Ponchik]

I am with PVC.



However, isn't there EMT conduit with a corrosion resistance coating.

 

[Cow]

Ocal.

 

[jumper]

Ocal.

Overkill for many applications here IMO.

 

[peter d]

I am with PVC.



However, isn't there EMT conduit with a corrosion resistance coating.

EMT is galvanized which makes it corrosion resistant. It still doesn't hold up in non-desert climates though.

 

[Haji]

If you want to use PVC, use sun light resistant grade PVC pipe (such as used for water lines). If you use ordinary wiring PVC conduit outdoors, the whole length may tend to sag in the long run.

 

[RICK NAPIER]

My business was at the Jersey Shore pvc over emt when ever exposed to the salt air.

 

[Cow]

If you want to use PVC, use sun light resistant grade PVC pipe (such as used for water lines). If you use ordinary wiring PVC conduit outdoors, the whole length may tend to sag in the long run.

You realize the pvc conduit sold over here in the US is sunlight resistant, right? And it stills turns purple in the sunlight and sags over time.

 

[rbalex]

We have been using RTRC (Article 355) for the Ports of Los Angeles and Long Beach for exposed (under pier) applications. It's more expensive than either EMT or PVC, but far less expensive than PVC coated RMC.

While no manufacture is currently ?listed? for greater support spacing than Table 355.30, with proper structural engineering documentation, it can also be shown to require far fewer supports. The problem with ?listing? is it takes an engineered evaluation of loading. [See Section 355.30; especially, 355.30(B)]