EMT Condensation

[AffableCurmudgeon]

Hello, would appreciate some help from some electricians or builders.

I have a 2nd floor bathroom with tall vaulted ceilings in Chicagoland. Since the ceilings are vaulted, there is not much room between the ceiling and the roof. As far as I can tell there is fiberglass insulation bat between the drywall and roof sheathing.

This winter, I noticed water dripping from a ceiling light fixture in the bathroom. I took off the fixture and found water coming out of the EMT conduit. Fiberglass insulation bat around the conduit was dry.

Thinking that this is a bathroom, and the fixture is close to the shower, and that the conduit in the ceiling is likely very cold, I figured that warm moist air is getting in the conduit and cold temperature in the ceiling is condensing the water and that condensate is dripping out of the EMT.

I bought some duct seal (putty) and stuffed in on the fixture as well as the light switch end of the conduit. I still am getting some water drips.

I can't access the conduit in the ceiling. The ceiling is vaulted and covered with drywall. I am assuming that there is a single run, without any junction boxes, between the switch and the fixture. There are only two (+ and -) wires entering and exiting the conduit.

So, with this background, I have a couple of questions.

1. Is there a trick to stuffing the conduit ends with the duct seal? Is it possible that I did not apply it properly around the wires in the conduit? Is the duct seal the right way to go?

2. Can I spray the Great Stuff foam on both ends of the conduit instead? It will likely seal better around the wires.

Thanks for your help.

 

[dw1]

Wow, I wiukd try to find out how the outside cold air is getting in the conduit and then seal

 

[AffableCurmudgeon]

I don't think outside cold air is getting in the conduit; inside warm air is getting the conduit. The conduit is in the unconditioned space under the roof and above the celing. There is cold air there that is cooling the conduit and condensing the moisture in the warm air in the conduit.

 

[rockwithjason]

i don't use duct seal for this, i use clean silicone. it seems to be much better at keeping the air from moving. keep in mind that you may have some drips for a while until all of the condensate is drained from the pipe.

 

[dw1]

Sorry, I meant to type "in to" the conduit, I would not put any duct seal down low, if condensation builds up and the dam lets go, you could have a bigger problem

 

[larry_g]

Take a look at the fixture. Is there seal broken there that is allowing the moist air into the junction box/conduit? Should you consider sealing the fixture to the ceiling or junction box preventing moist air from getting to the cold metal parts and condensing? Is your bathroom vent working to remove moist air during bathing times?

lg
no neat sig line

 

[The FIB]

They make foam gaskets for electrical boxes, the trick is to keep the warm moist bathroom air from entering the box.
Just to be safe, when you reinstall your ceiling fixture make sure the wire nuts are pointed up, so the don't collect water at the splice.

 

[rsieracki]

i just rewired my home built in 1952.. i was amazed at the rust and **** the came out as i pulled the old wires and and then again as i pulled the new wires in... made a filthy mess and i had to vacuum out the boxes.

i rewired due to frayed cloth insulation over dry rotted rubber insulation. wire marked as 'Crescent 12ga HR heat resisting wire' solid copper and it was 'stuck' to the conduit in some places made for lots of extra work pulling it out which sucked.... almost done

 

[toplessHO]

i just rewired my home built in 1952.. i was amazed at the rust and **** the came out as i pulled the old wires and and then again as i pulled the new wires in... made a filthy mess and i had to vacuum out the boxes.

i rewired due to frayed cloth insulation over dry rotted rubber insulation. wire marked as 'Crescent 12ga HR heat resisting wire' solid copper and it was 'stuck' to the conduit in some places made for lots of extra work pulling it out which sucked.... almost done

yep insulation has come a long way with thermoplastics vs rubber /fabric covered
lucky for you it was in conduit.