RMC & EMT in Wet Areas

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dasarmin

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I've always specified RMC for wire runs in any area that might be wet, for instance a production facility room with Chillers, Towers, Pumps, Tanks, etc. The NEC say EMT can be used in wet areas with the proper corrosion protection.
What's your thought on RMC or EMT in Wet Area?
Thanks.
 
dasarmin said:
I've always specified RMC for wire runs in any area that might be wet, for instance a production facility room with Chillers, Towers, Pumps, Tanks, etc. The NEC say EMT can be used in wet areas with the proper corrosion protection.
What's your thought on RMC or EMT in Wet Area?
Thanks.
Click to expand...

EMT does not require any extra corrosion protection in wet areas, it is often used in wet areas. The requirements found in 358.10(C) (EMT) mirror the requirements in 344.10(D) (RMC) for wet locations. If you have EMT concrete or direct contact with the earth than 358.10(B) kicks in.

I do not like to use it outdoors in this area as the weather conditions seem to rot it away quickly but in other areas of the country it is often used exposed to the weather with good results.
 
We use it outside here with no problems. But rooms that are constantly damp or humid, we'll might run rigid, but I prefer pvc. Constant humidity combined with chemicals(chlorine) will kill galvanized pipe quickly. PVC coated rigid if it's a really harsh environment.
 
As I start to post an opinion, decades of installations come to mind. Many years ago I would not think of anything other than rigid in wet locations, but I have found that those jobs I installed to last for ages disappeared with the structures as the facilities closed :) (once you reach 60 "temporary" takes on new meaning)
Today, unless specified otherwise, I would have no problem installing EMT is a "wet" location, but I would be careful to follow 300.6(D).
 
I have never had a problem with EMT, but go up on some older roofs and see what it looks like after a few years, though I'm not sure that RMC fares much better. I would think it might depend on what you "cared" that it looked like later.
 
The only thing RMC has going for it over EMT (at least corrosion wise) is that it takes longer to rust through.

If either is in an environment where minor corrosion is a problem, it should be painted.

Or use plastic or plastic coated in the first place, or a tray as another poster suggested.
 
dasarmin said:
I've always specified RMC for wire runs in any area that might be wet, for instance a production facility room with Chillers, Towers, Pumps, Tanks, etc. The NEC say EMT can be used in wet areas with the proper corrosion protection.
What's your thought on RMC or EMT in Wet Area?
Thanks.
Click to expand...

Are these rooms really wet locations?
 
I've never had a problem "Corrosion" wise in chiller rooms. Cooling Towers
are a different animal. I stopped using EMT in cooling tower pads because
you can actually see your EMT corrode due to the constant water vapor and
chemicals they use to treat the water.
 
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