[Randy Myers]

I have a BRAND NEW LENNOX split system. It's hot here right now and the new system is still working properly as in it is still cranking out ice cold air and keeping my house at the temp that I set it at but both of the ducts that feed the house with the cool air are sweating profusely and dripping all over the floor.

Obviously I will be calling the Lennox dealer who installed the unit but I would love for you to give me a bit of education so that when they come out, they don't try to blow smoke up my butt and tell me that this is normal. I know that it is not because with the system that I had for the last twenty years, those same supply feeds never even got moist, let alone so soaking wet that they are dripping all over the floor.

The only thing that I've read so far is the possibility of a clogged line on the condensation pump. I can't imagine that in only one months time, that there could be enough algae to be clogging anything.

HELP!

 

[skibme]

Where is the unit located? attic, crawlspace...Probably just a lack insulation in or on the ducts.Ideally the ducts should be insulated either inside or on the outside.Post some pics.

 

[Fabrk8r]

You saw "BRAND NEW" system...how long has the unit been running and are the ducts located in the conditioned space?

If the unit has only been running for a few hours and the humidity is still high then the duct that is in the conditioned space will sweat until the humidity level drops below dew point. If these sweating ducts are in the attic or crawlspace, then as skibme said, they should be insulated.

 

[Randy Myers]

Thanks for answering. I can't take photos right now but the ducts are the supply ducts coming off of the unit which is in the basement.

I'm pretty sure there is no insulation on the inside of the ducts and I know for a fact that there is no insulation on the outside. Is this the usual reason for this kind of sweating on the ductwork?

Is this what I should suggest if the tech tries to tell me that this is normal?

 

[Randy Myers]

The system is about one month old. Has been and still is working fine except for this sweating duct problem.

The system and sweating ducts are in the basement. I keep the supply vents closed in the basement because it remains plenty cool enough down there without them.

I guess I'm looking for things to know and say when the technician comes to the house.

 

[Fabrk8r]

You have 4 choices.

1. Open supply and return vents in basement to condition the air and remove humidity.
2. Raise temp at thermostat to the point that the temp of the duct is higher than the dewpoint of the air in the basement.
3. Insulate the duct that is sweating.
4. Use dehumidifier in basement.

 

[skibme]

This might be the problem. I keep the supply vents closed in the basement because it remains plenty cool enough down there without them.



Some companies don't insulate ducts in conditioned spaces. Wipe the moisture off completely, then open the vents up.

 

[Randy Myers]

Thanks Folks!

 

[teddy bear]

Give the a/c a chance to dryout the home. The t-stat should be set on "auto" blower to max the amount of moisture removed. Close all outside windows/vents in the crawl/basement. Monitor the temp/%RH throughout the home.
Colder ducts sweat more but colder air is dehumidified more. You want 50%RH in a finished basement. If only a small amount of duct sweats, insulating the cold spot with a closed cell foam is good. <60%RH in an unfinished basement. After maxing the dehumidification from the a/c, get a good dehumidifier to maintain 50-60%RH in the space.
The Santa Fe Compact is real good one.
Regards TB

 

[coolperfect]

Check supply and return TD at A/ H

 

[Randy Myers]

Teddy Bear,
I haven't checked in the basement but the RH on the main floor has remained between 45% and 55%. Only half of the basement is finished but we never use it as such.

How do I "max out the dehumidification of my system?"

Why have the T-stat on auto as apposed to on all of the time. The later was suggested by the installers when they put it in. It has a two speed fan and when the AC is not running, the fan winds down to a slower setting but continues to run. Is this not the right way to go about it?

Cool Perfect,
I'm not a pro or even a DIYer. I don't understand your answer because I don't know what the abreviations stand for. Please explain further. Thanks.

 

[coolperfect]

The temp. difference between supply and return at the unit.A unit that does not move enough air will cause the supply to run colder .The difference should not be more than 20 deg. With 17 best

 

[Randy Myers]

OK, how does one take the air tempurature inside the supply and return ducts?

If the system is not moving enough air, what would be the cause? This new unit is 1/2 ton bigger than the old unit. The reason for this is because the old 2 ton unit was never able to get down to target temp when it got hot outside. If this system is oversized for the duct work, could this be the problem?

If so, what in the hell can I do about it now?

 

[cuchulain]

to take the temp put a thermometer in the return grill and put on in the closest supply grill.

Yes duct work that is too small will also cause condensation, as well as other problems. The reason to have the stat set for auto is so after the cooling cycle it has a chance to dump all remaining condensation off of the coil and allow it to also drain out of the drain pan. if water is allowed to stay on the coil or in the pan it will put humidity back INTO the house.

Again if the ducts are not insulated and the humidity is high in the basement they will sweat. open up some of the grills in the basement to help it move some air around and allow air from the basement to get to a return (if there isn't one in the basement) so that it can help pull the humidity out.

 

[Randy Myers]

OK, so allowing the fan to continue on slow when the AC is not running as apposed to having the fan turn off while the AC is not running, causes a situation where the system is not able to

"dump all remaining condensation off of the coil and allow it to also drain out of the drain pan?"

 

[rojacman]

o yea.....

Check supply and return TD at A/ H

ditto+.....Jack:cheers:

 

[23caps]

Humidity in basement is to high. Comfort level is 30-50. Most duct has about an R4 insulation value which is not much. Open all the supply and return vents. Run fan in auto.
Ask tech to chack Delta-T.

 

[Randy Myers]

Update After Visit From Technician

A little history for those of you that might be starting fresh with this one:

I’ve somewhat recently “upgraded” from a 20 year old 2 ton, split system Heil that was never quite able to bring the temp down to 72 when it got past 82 degrees outside to a 2.5 ton Lennox which is able to get down to temp with no problem so far. I was going to say “without a sweat” but you’ll soon see that that isn’t the case.

I have a small cape cod with virtually no insulation that is like a little brick oven in the summer time.

The old and new systems are/were split systems with the furnace and coil in the basement. The basement is half unfinished. This is where the system is located. The other half is finished but it is a very rare occasion that we ever use it. For the past 20 years, I would rarely condition the basement in the summer and only a little in the winter.

Problems with the new unit consist of major sweating on the two supply trunks that come off of the system and it doesn’t appear to be dehumidifying as well as I would have hoped.

The tech from the company that installed the unit came out about two weeks ago. He checked a few computer settings and then measured the supply and return temps, which were 58/74 for a difference of 16. He said that the difference should be more like 20 and also that the system had been set up as if it were a 3-ton unit as apposed to a 2.5 ton. He also said that the unit outside was charged too much.

He changed the fan speed from 1270 CFM to 1105 CFM, took some of the charge out of the unit outside and then got temps of 56.7/75.7, which he seemed to be pleased with. He said that the unit was now set up exactly as it should be. While he was here, he also called the salesman who sold me the unit, who also doubles as a supervisor. The salesman/supervisor said that in a few weeks, he would set up an appointment to have the supply ducts insulated and a small return cut into the unit itself. This last part has not taken place yet.

What the tech did made the run cycles a little bit longer but has had absolutely no effect on the sweating problem and very little effect on the humidity problem.

As per suggestions from this thread, a little more than a week ago, I changed the thermostat from the fan being on all the time, to Auto. This DID have a slight effect on the dehumidification of the main floor. It went from hangin’ around 51-53% to 49-51%. Not much but at least headed in the right direction. Obviously the changed fan setting had no effect the condensation problem.

As of yesterday, I started experimenting with another suggestion from this thread, which was to open the supply vents in the basement to condition the air down there. This had a fairly dramatic effect on the sweating. Unfortunately, at the same time, it pretty much turned the unfinished part of the basement into a freakin’ MEAT LOCKER!

Here is a link to some photos of my situation. It’s the sweating at it’s worst when I don’t have any supply vents open down there. It will also show you the different shapes and sizes of surfaces that might need to be insulated.
http://jammer.zenfolio.com/p902799442/h33584464#h33584464



OK, question time. Please keep in mind my goals of controlling the condensation hopefully without using the supply vents and making it so cold down there. Also I would LOVE it if I could get the RH on the main floor down to at least 45% and hopefully between 40-45%. I really don’t think that this is too much to ask after paying seven grand for the furnace and AC, do you?

1.Not knowing much about this stuff, I’m afraid of having the supply ducts insulated. I have this vision that it will only hide the problem as apposed to correcting it. I have thoughts of a wet gooey mess behind the exterior foil where all kinds of nasty mold and crap will develop. Also, in order to insulate, there would be 2 or 3 damper levers covered up. Should I let them insulate the supply ducts?

2.As you can see from the photos, there are round supply ducts and the older rectangular supply ducts and there is even quite a bit of condensation where they joined the new unit to the main supply duct. If I let them insulate all of those areas, how should it be done and what would be the best materials to use.

3.Should I let them “cut a small return” in the unit itself? Again, not knowing much, this “feels” like hacking up a brand new system.

4.Keeping my goals in mind, please explain in layman’s terms, the exact steps that YOU would take next if you were me?

If you could answer my numbered questions as asked I would REALLY appreciate it. Please feel free to add whatever else you think is necessary for me to know but I just know that I will personally understand things better if you answer what I’ve asked.

If you’re still with me, GOD BLESS YOU :angel: and thank you very much for your help!!!

 

[fxb80]

1. The condensation is not coming from the duct itself, it is coming from humid basement air condensing on the cold duct. Insulation will prevent the air from reaching the duct, so insulation will fix the problem, not cover it.

2. We would use 2" foil backed insulation with foil taped joints.

3. It's perfectly normal to add a return in the side of a furnace, but not the back.

4. Frankly, it's too late for a "next step" other than insulating ducts and adding return if needed. The first step to control humidity is improvement of the structure since most of the humidity is coming from humid outdoor air infiltrating the structure. Add a vapor barrier, seal penetrations, add insulation. Then have a load analysis done to find out what size A/C is needed for the improved structure; it will be noticeably smaller than the size needed for an unimproved structure. The reason the A/C should be calculated carefully is that it should be just big enough. Just big enough means that it will run almost continously when the outdoor temperature is at the normal maximum high. It needs to run continuously because air conditioners are not dehumidifiers per se. They remove humidity but to effectively control humidity the air must be reheated after being cooled and dehumidified. In an actual dehumidifier the unit does the reheat function. An air conditioner doesn't have a reheat function, heat load from outside and inside is the source of reheat. So, dehumidification will be most effective when the heat load from outside and inside matches the amount of cooling being done by the A/C which will cause the A/C to run more. Since the normal maximum high occurs infrequently, most of the time the A/C will be too large to work well as a dehumidifier. Current state of the art dehumidification control of A/C units will not actively control humidity, having no reheat function for times when there is insufficient heat load to make the unit run continuously. Premium units may have two stages of cooling or even variable cooling that will enhance dehumidification by more closely matching the unit's cooling capacity to the load on the structure, causing the unit to run more. A premium thermostat with humidity control will not actively control humidity, it's function is to slow down the fan to enhance dehumidification and also to offset the cooling setpoint so that the apparent temperature is more stable. The actual humidity may not change or may even go up with a humidity controlling thermostat. Normal comfort range for humidity is 40-60%. I work in a climate where if indoor humidity is 50% we consider the equipment to be working very well. When a customer is concerned with actual comfort versus an arbitrary humidity target and humidity is less than 60% we don't have humidity control complaints when a properly sized premium system has fan slow down control and cooling setpoint offset.

In your case, if you want to further control humidity buy a dehumidifier.

 

[Randy Myers]

FXB80,
Thank you very much for taking the time to help me out. I appreciate it.