I appreciate the suggestions for insulating the registers. Unfortunately I already tried that and put quite a bit of the yellow batt insulation around them. I even insulated around the nearby can lights (using LEDs so no risk of overheating) and they still sweat.

quote:
Are the sweating registers closest to the air handler/supply plenum, i.e., shortest duct run?

Yes, only the two registers closest to the plenum are sweating. All the other registers are fine.

quote:
What do you set your thermostat at?

I have two units and this one is on my kitchen/living side. I keep it about 71 during the day and 73 at night while we sleep. I like my bedroom a good bit colder but that's for the other unit.

quote:
You monitoring your house humidity?

I haven't been but I notice on the thermostats, my bedroom side (the newer 2012 unit) can keep it around 49%-55% humidity. The kitchen one (2003 R22 unit) can only maintain the humidity between 60%-70%. So I think the massive air leaks in the kitchen are contributing to the sweating.

When I run my dehumidifier it reduces the amount of condensation on the registers and sometimes get rid of it entirely.

Here's a picture of my ceiling. There are a lot air entry points so I think I just need to start sealing stuff up.

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Posted by eng08

Member since Jan 2013

5997 posts

Posted on 6/25/21 at 2:26 pm to bapple

Your leaking hot moist air which is condensing at the vents.

Insulate and seal around cans and vents.

I had the same issue on a few spots - used a can of spray foam around all my lights and vents, then had guys come in to top off blown in insulation - no more condensation.

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Posted by CrawDude

Baton Rouge

Member since Apr 2019

5301 posts

Posted on 6/25/21 at 9:24 pm to bapple

Ok - can see from your photo the two registers are very close to the air handler/supply plenum, as the return air grill, is right behind them. You have short supply duct runs, and the ducts are not picking up much heat from the attic, blasting out cold air in the kitchen (I’m guessing the HVAC service included additional R-22 refrigerant), the metal grills are cold and the room’s air dew point temperature is higher than the temperature of the metal registers causing condensation on the grills. I suggest you raise the thermostat temperature to 74 for a couple days to see if condensation ceases when you raise the room temperature.

With high humidity in that area, It seems you do have significant air filtration (heat seeks cold, wet seeks dry) so sealing the lights, skylight, etc. even if it doesn’t solve the immediate problem will not be wasted effort. If need be have a blower door test conducted to determine areas and severity of air infiltration into the house - so you’ll know what areas to be sealed. About $300 for the test - I’m having a blower door and duct leakage test done on my house next week.

If humidity is indeed 60-70% in areas serviced by the 2003 unit you do have serious air infiltration, another issue with the 2003 HVAC or a combination of both. Your 2003 HVAC should be maintaining humidity near 50% in this heat with long HVAC run times, unless your HVAC is seriously oversized. Get a hygrometer to double check your humidity against your thermostat - posted a photo below of a cheap but good one that’s pretty accurate and can be calibrated - I have 3 of them.

Lastly I’m posting a good article to help you understand and further troubleshoot your problem. Why Do AC Vents Sweat