Comments on: Why Do Air Conditioning Vents Sweat?

By: RoyC

RoyC — Tue, 17 May 2022 15:16:05 +0000

Reducing the indoor airflow rate will result in colder supply air but it will also result in more latent capacity, thus lower humidity levels in the house. So lowering the airflow rate might help reduce this sweating.

Low refrigerant charge does mean lower evaporator pressure and thus lower temperatures in part of the coil, but the refrigerant flow rate is greatly reduced due to choked flow in the expansion device. The result is that much of the coil contains superheated refrigerant which results in the overall evaporator capacity being lower and thus the supply air temperature will be higher. So low refrigerant charge does not contribute to the grill sweating unless I am missing something here.

The biggest issue that I have seen contributing to supply register sweating is humid air from a vented attic leaking around the register. The solution is to seal and insulate where the supply duct passes through the ceiling or wall surface.

By: Joe

Joe — Tue, 29 Jun 2021 00:21:19 +0000

In reply to Sam (a.k.a., Traumatized in Tuscaloosa). Hi. Low refrigerant results in low temperatures in the evaporator. Low temps are a result of low pressures due to low refrigerant. If the coil is much colder than 40 degrees, it can result in colder than normal supply air (until the coil freezes). If the air flow is too low, it spends more time in contact with the coil, again, resulting in colder than normal supply air

By: Sam (a.k.a., Traumatized in Tuscaloosa)

Sam (a.k.a., Traumatized in Tuscaloosa) — Mon, 31 Aug 2020 18:43:27 +0000

You had me until this part:
You had me until this part:
“Why the supply vent might be too cold
…The two main causes of excessively cold vents are low refrigerant level and low air flow through the system.”
Are you telling me that supply air can be TOO cold, and that it could be caused by, among other things, LOW refrigerant levels or LOW air flow?
For the love of Air Supply! How can any of this be true?
Yours truly,
Traumatized in Tuscaloosa

By: Bill Lee

Bill Lee — Tue, 25 Aug 2020 18:29:30 +0000

In reply to abailes. The standing water is
The standing water is evaporated if the blower should be operated in the "on" position since the coil is not being cooled in the refrigeration process. If the drain is blocked, causing an overflow, then there is excess water in the equipment, on the floor, or around the coil, however the system is installed.

By: Jake Bruton

Jake Bruton — Mon, 24 Aug 2020 10:51:26 +0000

afishionados!!!!
afishionados!!!!

By: John Vansant

John Vansant — Mon, 24 Aug 2020 02:38:01 +0000

………Or, incorrectly
………Or, incorrectly installed “pull through” type evaporator coils – commonly found on electric air handlers, installed without a condensate drain trap. As these systems run they pull condensate water through the untapped drain line and instead of draining, throw water all over the face of the coil, re- humidifying the very air that the air conditioning system is intended to dehumidify.

By: abailes

abailes — Wed, 29 Jul 2020 20:46:33 +0000

In reply to Dumb Question. The easiest way to find out

The easiest way to find out if this is causing a problem is to measure the temperature of the supply air at the vents or the surface temperature of the vents themselves. If it's 50° F or below, it's probably a problem.

By: abailes

abailes — Wed, 29 Jul 2020 20:44:53 +0000

In reply to Andy Kosick. Good point, Andy. Lots of

Good point, Andy. Lots of house plants can be as bad as lots of aquariums.

By: abailes

abailes — Wed, 29 Jul 2020 20:43:58 +0000

In reply to Thomas Dugan. Thomas, yes, that can happen

Thomas, yes, that can happen with ducts in an unconditioned attic, but it depends on whether the leaks are predominantly on the supply side or the return side. With more supply leakage than return leakage outside the enclosure, the house will be under negative pressure. Here's an article I wrote about that:

The Sucking and the Blowing — A Lesson in Duct Leakage

By: Dumb Question

Dumb Question — Wed, 29 Jul 2020 20:12:18 +0000

Allison-
Allison-
You Wrote… I’ve also heard of cases where the air flow was too low in multi-stage or variable capacity air conditioners operating at low speed. Ideally, the refrigerant and air flow change together in just the right amounts, but complex systems don’t always do what you want them to do. Sometimes the air flow is fine at one speed but too low at another speed.
How would I confirm or eliminate this as being the issue? Flow hood I suppose?