I'm sitting here in my office at work and the A/C unit hangs right above my head suspended from the warehouse ceiling. It works fine 90% of the time. My issue is that when it gets really humid out on a hot day there is a junction type box sticking out of one end of it that starts sweating really bad to the point that my ceiling tiles are destroyed and I have to have a bucket on the floor to catch the water. Can I just wrap some insulation around this box and maybe that will cause that condensation to go out the drain pipe instead of sweating thru the sheet metal?

 

Insulation couldn't hurt, I would also have the freon charge checked. If it is low it will cause the evaporator to freeze up and sweat more. These units are designed to drain from the drain only. If the junction box is sweating I would say that your charge is low.

 

Thanks for the reply.

Just to be clear, by "junction box" I am referring to a big box that all the vent hoses come out of leading to the individual vents around the office. It seems odd to me that it would sweat there. There is actually a large sheet metal tray under the entire unit EXCEPT for that "junction box".
Having said that, does it still sound like it may be a low freon charge?

 

If it's supply air duct in an unconditioned space, it needs to be wrapped or insulated.

 

OK. It's not going to be easy but I'll try to wrap it up. It's like 9' up in the air and I have to get up between the ceiling tile frames to get to it.

Thanks for the replies

 

The box is the air plenum. It needs to be insulated and securely taped to maintain the vapor barrier seal that keeps condensation from forming on the outside of the sheetmetal. Make sure you seal all edges of the insulation to each other and to the end of the unit. Wrap each flex duct takeoff with insulation as well and seal to the plenum box insulation and the flex duct insulation, or you will have more dripping condensation. As far as the charge, I would suggest that you check your filters 1st. Dirty filters slow airflow which will cause your coil to freeze up, even with a correct charge. If your filters are extremely dirty, you might call a service tech in to clean the evap coil, condensig coil, check the charge and clean the drain pipe. Doing this might actually lower the electricity bill enough to make a substantial savings.

Gary

 

OK. I'll get a roll of that metal tape and tape the be-jesus out of everything and report back.

 

You need to use FSK (foil skrim kraft) tape. It is silver, flexible and has strings in it to give it strength. If you use foil tape, it is less flexible, will not seal well to the insulation and will cut the dogpoo out of you should you rub the edge of it while trying to seal it to the insulation.

Gary

PS sorry I responded so late, but I have been out at jobsites ALL DAY.

Gary

 

Well, I am getting this message too late. I got it all wrapped up and am testing it to see if the sweating stops. Today all was well but I want to give it a few days. Before I put the new ceiling tiles up. I'll get a roll of the tape with the strings in it and go over everything again. Thanks for the tip.

 

take pics after the insulation soaks up all the condensation and falls on your desk

 

LOL. Funny that you say that because I think about that quite often.....

 

Duct is insulated or lined from the inside when its made and spot welded in place.

You need to wrap the duct with duct wrap, not fiberglass insulation. If done properly, the duct will fall down before the wrap does.

 

Ductwork can either be internally lined or externally insulated, but not both. Internal duct liner is used commercially quite a lot. External wrap is used in areas that are sensitive to having fibers that will migrate into the airstream such as hospitals and clean rooms. If you used foil kraft covered duct wrap and you sealed it well, you won't have any problems with condensation forming.

On another note, if you have stained ceiling tiles, you can use Cruex jock spray to cover up the stain. A General Contactor I worked for showed me this trick. Cruex has a powder base to it that matches the ceiling tile color perfectly. Paint will just soak into the tile and the stain will show through, unless you can find accoustical ceiling tile paint (hard to find).

Gary

 

I used the foil covered rubber type insulation that is self adhesive. It is very difficult to access the unit and I just wanted to make it as easy as possible. It seems to be working but I'll know for sure in a couple days.

 

Well, apparently the water continued to sweat out of the metal and was just accumulating inside the insulation until, you guessed it, it came pouring down onto the ceiling tiles. LOL
Back to square one........