Thread sealing RGS

electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Occupation
Electrician
I have to install several 100' runs of 4" RGS on the outside wall of a building. Does anyone ever put thread sealant on outside RGS? If so what would you use? Is electrical continuity for bonding purposes a concern? I normally wouldnt really care about some water in raceways, however this run has to enter in the top of some equipment ono one end, and strut supports have already been installed on the building so I cant slope the conduit slightly down away from that equipment.
 
Vertical runs of rigid always let water in at the couplings. I am not aware of a thread sealing compound listed for the purpose. Something like Crouse-Hind's STL will help, but it is not a sealing compound.

Rigid is difficult to seal as the conduit couplings are straight thread, and do not have the interference fit that seals plumbing piping where both the pipe and the coupling have tapered threads.

If the run is horizontal, you could install a C conduit body, just before you get to the equipment and put a drain hole in the conduit body, or install a T and put a drain hole in the plug facing down.
 
don_resqcapt19 said:
Vertical runs of rigid always let water in at the couplings. I am not aware of a thread sealing compound listed for the purpose. Something like Crouse-Hind's STL will help, but it is not a sealing compound.

Rigid is difficult to seal as the conduit couplings are straight thread, and do not have the interference fit that seals plumbing piping where both the pipe and the coupling have tapered threads.

If the run is horizontal, you could install a C conduit body, just before you get to the equipment and put a drain hole in the conduit body, or install a T and put a drain hole in the plug facing down.
Click to expand...
These runs would be horizontal. I could see more water entering in a vertical installation cuz you have a little "shelf" on top of each coupling. I like the idea of a C condulet with a drain hole, but I don't like adding several thousand dollars of cost to the job.
 
You could put polywater FST in the conduit at the equipment. However that will let the raceway fill up with water over time. Probably not an issue for you, but around here that could result in split conduits and crushing damage to the insulation when the water freezes.
 
don_resqcapt19 said:
You could put polywater FST in the conduit at the equipment. However that will let the raceway fill up with water over time. Probably not an issue for you, but around here that could result in split conduits and crushing damage to the insulation when the water freezes.
Click to expand...
Would a small drain hole in the side of the conduit just above the polywater FST (and above the equipent) be allowed?

Cheers, Wayne
 
wwhitney said:
Would a small drain hole in the side of the conduit just above the polywater FST (and above the equipent) be allowed?

Cheers, Wayne
Click to expand...
While there is code provision, in 314.15. for drilling drain holes in boxes and conduit bodies, I am not aware of one that permits a drain hole to be drilled in conduit.

That being said, if the hole is close enough to the end of the conduit so it can be de-burred, I don't think it would hurt anything, however, since the material and labor costs for 4" RMC are high, I would want the approval of my AHJ before drilling a hole in the conduit.
 
Functionally, you wouldn't really have a bonding issue, even with something like silicone. The threads faces will still touch metal to metal. The silicone would just fill the gaps around the threads. Not that code/listing would make that distinction though.

How many conduits are you running? Zoro has 4" C condulets for less than $100ea:




SceneryDriver
 
When doing refinery work, we always put a drain fitting in every run at the lowest point in the run. It was just a small fitting that screwed into a coupling that allowed the conduit to drain.
 
Rick 0920 said:
When doing refinery work, we always put a drain fitting in every run at the lowest point in the run. It was just a small fitting that screwed into a coupling that allowed the conduit to drain.
Click to expand...

Do you mean you just drill a hole at the bottom of a standard coupling?

I never thought about it, but with rigid at a coupling do the conduits butt up to each other or is there a gap?
 
electrofelon said:
Do you mean you just drill a hole at the bottom of a standard coupling?

I never thought about it, but with rigid at a coupling do the conduits butt up to each other or is there a gap?
Click to expand...
If you make them good-and-tight, they butt up against each other. Watertight sealing is doubtful, and there isn't space between the ends of the conduit for a drain hole in the coupling. Unless ... you cut a few thread off the conduit (and ream of course) or if making threads, stop a little short of a full thread.

For a number of reasons, I think it's a fool's errand to try to make rigid conduit watertight. Find a way to leave drains or use a cable.
 
All these large size metal conduits, troughs, enclosures, etc. are so expensive anymore. They must be making a killing on it. And the worst part is it's all pretty flimsy looking to me. There is no way any of it would even hold up to a minor forklift strike
 
electrofelon said:
Do you mean you just drill a hole at the bottom of a standard coupling?

I never thought about it, but with rigid at a coupling do the conduits butt up to each other or is there a gap?
Click to expand...

There are set screw couplings where you could back off the conduits a little on each side to make a gap. They are not cheap but some are available on Ebay for considerably less.
The malleable iron OZ/Gedney 29-400 has two flat areas for the setscrews where it should be easy to drill a hole. After drilling the hole, insert a bolt in it, push the conduits together, and tighten the setscrews. There are already holes there for the setscrews, so it's just another hole. :)

$69.99 or best offer from Ebay:
www.ebay.com

RSCP400 OZ-G 4" SET SCREW RIGID COUPLING | eBay

SKU: RSCP400 OZ-G.
www.ebay.com

vs. $265 from Gordon Electric:

 
Last edited:
electrofelon said:
Do you mean you just drill a hole at the bottom of a standard coupling?

I never thought about it, but with rigid at a coupling do the conduits butt up to each other or is there a gap?
Click to expand...
No. They make listed fittings with threads and a factory drilled hole in them that screw right into the couplings.
You can reference Eaton Crouse-Hinds CD1, Eaton Crouse-Hinds ECD15, and Appleton CRN50. These are just a few listed Explosion-proof
drain fittings or breathers.
 
Last edited:
TwoBlocked said:
If you make them good-and-tight, they butt up against each other. Watertight sealing is doubtful, and there isn't space between the ends of the conduit for a drain hole in the coupling. Unless ... you cut a few thread off the conduit (and ream of course) or if making threads, stop a little short of a full thread.

For a number of reasons, I think it's a fool's errand to try to make rigid conduit watertight. Find a way to leave drains or use a cable.
Click to expand...
Wouldn't the only way to ensure that the drain hole ends up on the bottom be to drill after installation? Is so, you’re going todrill through the pipe as well.
 
electrofelon said:
These runs would be horizontal. I could see more water entering in a vertical installation cuz you have a little "shelf" on top of each coupling. I like the idea of a C condulet with a drain hole, but I don't like adding several thousand dollars of cost to the job.
Click to expand...
What says you can't drill a hole in the GRC?
 
Rick 0920 said:
No. They make listed fittings with threads and a factory drilled hole in them that screw right into the couplings.
You can reference Eaton Crouse-Hinds CD1, Eaton Crouse-Hinds ECD15, and Appleton CRN50. These are just a few listed Explosion-proof
drain fittings or breathers.
Click to expand...
I am confused, those all thread into an female threaded opening. There is no open end coupling in the run to thread one of those into, and I can't see drilling and tapping a hole in the 4" RMC coupling to install one of those.
 
You must log in or register to reply here.
Top