Condensation in conduit - any fix?

[madmike]

Dear FORUM,
At a facility in Mayport FL., a room with many computers is kept cold enough to hang meat! The 225-amp sub-panel, located in and servicing that room, is fed from the building main panel. The feeder is routed above the false ceiling (which also acts as an A/C barrier) and then drops down to the panel.
Over the years, the water condensation inside the conduit due to the very cold conduit and the moist Florida air has caused severe corrosion of the service panel main lugs, buss bars, - OK, the whole thing should be scrapped out and replaced.

How can the condensation problem be resolved in a Code compliant manner?
Thanks.

 

[Dennis Alwon]

Dear FORUM,
At a facility in Mayport FL., a room with many computers is kept cold enough to hang meat! The 225-amp sub-panel, located in and servicing that room, is fed from the building main panel. The feeder is routed above the false ceiling (which also acts as an A/C barrier) and then drops down to the panel.
Over the years, the water condensation inside the conduit due to the very cold conduit and the moist Florida air has caused severe corrosion of the service panel main lugs, buss bars, - OK, the whole thing should be scrapped out and replaced.

How can the condensation problem be resolved in a Code compliant manner?
Thanks.

I am not sure you can stop the condensation. Is the main feeder the only conduit that is the issue? Are the more conduits in the panel entering from above.

One fix may be to bring the conduit into the side knockout rather then the top.

 

[crossman]

300.7 applies

 

[iwire]

As has been said, 300.7

Plug the ends of the conduit, that will stop the air from traveling through the conduit and the air is what brings in the water.

 

[Dennis Alwon]

As has been said, 300.7

Plug the ends of the conduit, that will stop the air from traveling through the conduit and the air is what brings in the water.

Will this really stop condensation or just stop the water from getting into the panel? :-?

 

[petersonra]

Will this really stop condensation or just stop the water from getting into the panel? :-?

The only way I know of to do this that actually works consistently is to arrange your conduits so they go through a drip leg that has a drain in it before entering the bottom of a box or PB. Its a major pain a lot of times to arrange it that way, but its effective. I don't know of any ways to effectively seal conduit systems that actually work that well over time. Even seals leak air when the air pressure changes. They just do it slowly.

 

[iwire]

Will this really stop condensation or just stop the water from getting into the panel? :-?

It will really stop the water. :smile:

The water does not just show up, it is brought into the raceway via the the air passing through the conduit.

When you work with a lot of walk-in freezers you learn this lesson fast.

 

[iwire]

The only way I know of to do this that actually works consistently is to arrange your conduits so they go through a drip leg that has a drain in it before entering the bottom of a box or PB. Its a major pain a lot of times to arrange it that way, but its effective. i don't know of many ways to effectively seal conduit systems that actually work that well over time.

If the issue is just condensation I can stop that no problem.

If the issue is water coming in from somewhere up hill of the raceway then I agree the only way is a place for it to drain.

 

[crossman]

A portion of 300.7 says "the raceway or sleeve shall be filled with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve.

If we want to get technical with it, I don't think that placing the fill material at the panel in the data room would be compliant. That would still allow warm air to get into the conduit in the cold area.

The fill would need to be placed at the spot where the conduit enters the cold area. Or, perhaps putting the fill material where the conduit/feeder originates would be okay.

Just my thoughts.

 

[HighWirey]

It will really stop the water. :smile:

The water does not just show up, it is brought into the raceway via the the air passing through the conduit.

When you work with a lot of walk-in freezers you learn this lesson fast.

It really will stop the water.

Plug the warm air end of the conduit using a generous amount of urethane foam. Leave the cold end open. Code compliant, I do not know, but it works.

Only worked in one freezer in my life, just down the street from madmike, and was I ever a newbie! Design temp was four degrees F. Stalactites from every HAD, and a few from the incandescent jar fixtures!

Best Wishes Everyone

 

[Lcdrwalker]

I will agree with Crossman. The conduit needs to be sealed where the temp change occurs. Expanding - insulating foam has always worked well for me in sealing conduit in walk-ins.

 

[Chris6245]

If at all possible (in other words if your changing out the panel anyway) I always try and install a junction box right before the conduit enters the "cold" air and seal the conduit opening on the cold side of the J-box. This prevents warm air inside the conduit in the warmer space from mixing with the cold air and no condensation will be possible.

 

[Pierre C Belarge]

It will really stop the water. :smile:

The water does not just show up, it is brought into the raceway via the the air passing through the conduit.

When you work with a lot of walk-in freezers you learn this lesson fast.

Ditto
I have to add some wording as was too short. :smile:

 

[ultramegabob]

you could install seal offs and chico...

 

[weressl]

Dear FORUM,
At a facility in Mayport FL., a room with many computers is kept cold enough to hang meat! The 225-amp sub-panel, located in and servicing that room, is fed from the building main panel. The feeder is routed above the false ceiling (which also acts as an A/C barrier) and then drops down to the panel.
Over the years, the water condensation inside the conduit due to the very cold conduit and the moist Florida air has caused severe corrosion of the service panel main lugs, buss bars, - OK, the whole thing should be scrapped out and replaced.

How can the condensation problem be resolved in a Code compliant manner?
Thanks.

Install a junction box at the inside/outside passage of the conduit and pack the conduit entering into the inside with duxseal.

 

[jflynn]

It really will stop the water.

Plug the warm air end of the conduit using a generous amount of urethane foam. Leave the cold end open. Code compliant, I do not know, but it works.

Only worked in one freezer in my life, just down the street from madmike, and was I ever a newbie! Design temp was four degrees F. Stalactites from every HAD, and a few from the incandescent jar fixtures!

Best Wishes Everyone

Be careful with the foam-I had an inspector ask if it was listed for conductors,after researching the listing it did not clearly state it was listed for the purpose we were using it...

 

[madmike]

Condensation in conduit - any fix?

Thanks for all the great comments and suggestions.
The Code is very clear. Will both re-route where possible and
seal both ends.


Regards all - MadMike

 

[dnem]

Plug the warm air end of the conduit using a generous amount of urethane foam. Leave the cold end open. Code compliant, I do not know, but it works.

Yes, the water vapor is coming in from the warm side. . Definitely seal the warm side. . But if you also seal the cold end, if a hole/crack forms in the warm end seal, you have a backup.

Code compliant, yes. . A single spot seal is code compliant. . As 300.7 says, "an explosion-proof seal shall not be required." . You don't have the specs for seal-offs that you have in a 501.15 hazardous location. . You just have to stop air travel.

Be careful with the foam-I had an inspector ask if it was listed for conductors,after researching the listing it did not clearly state it was listed for the purpose we were using it...

Yeah, some foams will eat the insulation. . Check the listing.