Dealing with hood duct condensation

My two hoods are vented with outside air through a pretty short run of ducting. Probably 5' on each side of the two lights.

As it's getting colder, the inlet duct was condemsating pretty badly and dripping on the girls. I put insulation on it yesterday and now the hoods and the outlet pipe were dripping. There was even a small pool of water on the glass of the first hood!

Any suggestions?

Thanks

Remove the insulation. You're trapping the condensation and making it worse. I've had the same problem.

Oh, and increase the air flow...

increase the airflow? How would that help things? It seems that that would make things worse if anything. I already have a 440 cfm fan pulling through a straight line of 12 feet of house. Plenty of airflow... I'll try and remove the insulation.

It seemed the insulation was just moving the problem "farther down the line"

You need to boost the airflow further down. I'm no HVAC pro or anything, but I had a similar problem. The condensation seemed to happen because the air wasn't moving out fast enough. I could be wrong, man. I don't know... Perhaps your lines are too cold. Perhaps your problem is that your air in the line is too cold and the outside temp is too warm... I really don't know.

I'd like to continue acting like I know what I'm talking about, but I've experienced something very similar, and it was caused by trapping the cold air in the line. By pushing it out faster, you have a lesser chance of condensation buildup. The fans don't really make the air "colder". I know you must think I'm insane.

Well, I think I'm going to have to dispel the illusion of knowledge on this one. Sorry man. Condensation forms when warm moisture laden air is cooled rapidly. So the warm moist grow room air is being cooled rapidly when it comes in contact with my ice cold ventilation ducts. I thought insulating would help alleviate this, but it did not. increasing ventilation would increase the amount of cold air coming in..thus more condensation.

I'm thinking I need to tape a towel or something around the ducts and just live with condensation during the winter.

I apologize. I was thinking your output vent was condensating. I am an ass. I apologize. I thought the air was condensating as it exited towards the cold air outside.

I believe that insulating the line will slow down the condensation process, but inevitably it will push the condensation down the line and potentially into your room.

I think you can use a desiccant filter.

Links you may benefit from:
http://hvac-talk.com/vbb/archive/index.php/t-132191.html
http://www.google.com/search?&rls=en&q=desicant+filter&ie=UTF-8&oe=UTF-8

not at an ass at all. Seems you and I have our own little thread. LOL. Thanks for the links though. They really don't offer a whole lot of solutions as it is simply a physics matter and the fact that the air ducting is really cold and the room is very warm which any way you slice it equals condensation.

When I insulated the first section of pipe (leading from the inlet to my first hood). It just kept the air cooler longer and caused condensation to develop on the hoods. I guess a longer run of hose would help warm the air up before it hits the hoods but the only real problem is the dripping so I might as well just address that with some towels or something. Seems weird that others haven't had the same problem.

Thanks again for the links.

The heavier cold air from outside is able to hold more condensation, when it goes through your op it's warming up and releasing its condensation. If you are needing heating because of outside temps getting colder you may be able to use some of the heat from your light to heat your op. I heat my mother room etc. and when the lights go out I'm on electric heat. It is important to make sure that when ventilating you maintain either positive or equal atmospheric pressure in the op. Plants don't do so well in negative pressure. I think if you reduce(providing you are within proper temp levels) the airflow it should reduce the amount of condensation because you will be drawing less cold condensed air through the pipes. In winter I open my bonnets.

how about a box inside to warm the outside air a little befor pumping through your ducts?

mrmadcow said:

how about a box inside to warm the outside air a little befor pumping through your ducts?

Click to expand...

I'm not sure I am picturing this correctly. I can't really see a way around it as it is simply a matter of phyiscs.. the ducts are cool from the outside air and the air in the room is warm and moist...thus condensation is going to occur. I tried insulating but all that happened was the insulation got soaking wet. For right now I just added more inlet house and a 90 degree elbow before the hood to try to get the condensation to drip in one place.

Bump.... what solution did you find for this, i am having the same problem...

legallyflying said:

My two hoods are vented with outside air through a pretty short run of ducting. Probably 5' on each side of the two lights.

As it's getting colder, the inlet duct was condemsating pretty badly and dripping on the girls. I put insulation on it yesterday and now the hoods and the outlet pipe were dripping. There was even a small pool of water on the glass of the first hood!

Any suggestions?

Thanks

Click to expand...

Hiya M8,

The difference in temperatures between the OA and the lights heat load are causing the dilemma. Is there any way you can pull your light venting air from another source other than outside till the weather warms up to the point where condensation will no longer form? You can stop the condensation, but at the cost of really ripping the air through the duct so that the air does not have time to drop it's moisture in your ducting ( noisy and inefficient). As long as there is a temperature differential of say 35-40 degrees ( easy to accomplish with winter air and a HPS/MH bulb) there will be condensation. Other than "pretreating" the intake air to heat it up a bit there are not to many solutions to this issue. If the moisture is in the duct, it will eventually take its toll on your equipment. Insullating the duct will only serve to create more condensation, as the cold air is kept colder longer and it can "wick" water to unwanted locations.

Peace

Asmallvoice

bird mcbride said:

Plants don't do so well in negative pressure.

Click to expand...

Love the crazy stuff folks post here! IF that was the case, then you'd only be able to grow at sea level, and not at altitude. A few Colorado folks here would beg to differ.


ASMALLVOICE - great advice

well i used the ambient home air to pull for air now and it fixed the condensation, but now i have positive pressure, really weird as i have no intake....just a sealed hood...