I'm having moisture problems running my central AC in sub-20F weather.

[Lapides]

Hi, I was hoping someone may be able to help me out.

I grow with 6kW in a 600 sq ft space and have a central AC unit dedicated to cooling everything. It does a great job, even when its 98 degrees outside.

However, I've started to notice moisture coming down from the exhaust where all of the hot air from the room is sucked out of the room. The AC unit is on the roof.

I'm guessing it's a condensation issue with warm air from the room hitting freezing cold ducts outside.

Is my guess correct? Is there any way to keep this from happening?

Thanks in advance to anyone who can help.

 

[grow nerd]

Insulation.

 

[RedRain]

^ grow nerd speaks the truth

the air hits the vent and the moisture in the air forms water droplets, just like a can of cold beer on a warm day

they make insulation for this purpose. shiny aluminium paper on one side and insulation on the other.

easy fix.

 

[Lapides]

So this insulation goes around the ducting that is exposed to the outside? This insulation holds up to the elements well?

 

[grow nerd]

Depends on the type of insulation and how the outside is laid out, but in general yes. You're probably not gonna wanna use any exposed fiberglass insulation for interior walls or anything, since that's unlikely to "hold up to the elements". Maybe something like Reflectix, or anything else that might be rated to stand up.

 

[Lapides]

After thinking about it, it doesn't seem as though I will be able to insulate enough ducting to keep the condensation away. If I insulated the duct that comes out of the roof into the AC unit, I still have a fair length of duct in the crawlspace that I have no access to. That part is getting very cold too.


The way I have the thermostat set now is COOL - ON and FAN - AUTO. So nothing happens and the ducts get ice cold until the temps get too high and the AC kicks on. Then the warm air is exhausted and hits ice cold metal and causing the condensation.

I'm going to try turning the FAN to ON with the hopes that the ductwork will stay warm from the air circulating constantly to keep condensation from forming.

The more I think about it however, I think condensation will still happen with the cold outside and the constantly warm duct, maybe even more.

I'm thinking I'm going to just tough it out and have some pans on the floor and hit the wet spots with bleach to keep mold/mildew away.

 

[grow nerd]

If the intake is large enough, maybe try lining it securely on the inside with some rigid foam.

Having the fan run continuously would help, too, for more than just condensation.

 

[Lapides]

The rigid insulation is a pretty good idea. But I can only get a couple feet-worth in until the duct makes a 90 degree turn.

I'll run the fan continuously and see how that does.

Thanks for your help.

 

[grow nerd]

On second thought, having the fan run continuously would probably increase the amount of condensation. Not necessarily a bad thing as long as you can contain it. Consider it an extra cheap dehumidifier.

 

[Babbabud]

A room that is not so cold to use as a bellows room would surely help. Ive had this problem before myself and have started drawing air through a carbon filter in my veg room as a place to pull air thats not sooo cold. Before the carbon I could smell the veg plants ... now it seems to work out well. But as long as you keep drawing ice cold air in I think you will have the same problem. Ive tried the insulated tubing but still had rain inside the tube.... the diff in temp is just too much in cold country. A place to draw warmer air is the fix. I use outdoor air most the time but once it gets too cold I move it over to the billows room

 

[Lapides]

I appreciate all of your input everyone, thank you.

Keeping the fan set to ON seems to have solved the problem so far. But it HAS been a tad warmer lately, so we'll see.

I'll post back in case anyone else has this problem.