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Condensation @ supply grill

roundtable's picture

I want to know some of things that may cause condensation at the supply grill in the upper level .....the grill is in the ceiling....the condensation only happens at the two grills closest to the unit.....any ideas??

(post #116098, reply #1 of 11)

Is the duct work in the attic?

My guess is that the condensation is actual in the attic and running down.

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William the Geezer, the sequel to Billy the Kid - Shoe
. William the Geezer, the sequel to Billy the Kid - Shoe

(post #116098, reply #2 of 11)

Running down what, I thought mabey the air was too cold...so I adjusted the temp, (warmer) and turned the fan speed higher....still sweating..
The duct is sealed & insulated well

(post #116098, reply #5 of 11)

But the grill is cold. If hot, warm attic air is reaching it then you will get the condensation on the grill or housing.

.
William the Geezer, the sequel to Billy the Kid - Shoe

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #116098, reply #3 of 11)

What causes it? Cold and moisture.

The source of the cold is obvious - now figure out the cause of the moisture.

A couple of possibilities: two high of a temperature differential across the AC coils

Too high of a system capacity so that the AC shuts down before there is not enough dehumidification and thus high humidity in the house air.

Do you feel clammy when the AC is on? Break a sweat even with little exertion? -an indication of over capacity.

I'll toss in a third one -- for free<G>

Leakage of humid air from the attic around the supply grill - it that's the case, is your ac pressurizing the air up there? How? It ain't supposed to ....





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(post #116098, reply #4 of 11)

Let me add this, there are only two grills in the house that are sweating, they are very close together, in the open foyer area.

(post #116098, reply #6 of 11)

Rountable,


Is this something new?


Are the registers partially closed?


Did you recently close any other registers?


My guess is that cold air is coming out of these 2 registers at a very high velocity and creating extra cold grilles.


 

(post #116098, reply #8 of 11)

This is a new house, the homeowner started moving in about two weeks ago and this is one punchout item I can't quite get punced out. My hvac contractor has been in 3 times doing most things mentioned here, we have raised the air temp and turned up the fan speed, also shut down the humidifier and droped the temp to 68 to see if running the system longer would help ......still wet.....Also my contractor said he has added mastic all around and the grill is sealed well....we used an insulated flex line to feed the grills.... I don't know what else to do.....But the problem needs to be fixed.....I am not sure what part he says he changed I think a valve he says may not have been functioning properly...still wet....???????????????
Thanks Guys

(post #116098, reply #9 of 11)

New house may suggest a significant (and temporary) increase in the moisture in the air. Concrete has a lot of water to get rid of in the first year, as does the joint compound, paint, water based finishes, etc.

Perhaps your problem will go away in 6-12 months when the moisture levels normalize.

 


Jon Blakemore

RappahannockINC.com

Fredericksburg, VA

 

Jon Blakemore

RappahannockINC.com

Fredericksburg, VA

(post #116098, reply #10 of 11)

What is the humidity inside the home?

(post #116098, reply #11 of 11)

If it's a new house then the humidity inside is likely much higher than normal. (Almost all building materials, and drywall in particular, are excessively moist when new, and it takes a year or so for humidity levels to get to normal.) You certainly shouldn't have a humidifier running, and might want to consider a temporary dehumidifier.


As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #116098, reply #7 of 11)

Not unusual. Cold air mixing with warm, moist air at the outlet. A sort of venturi effect draws air from the ceiling around the grill towards it, and the mixing there results in air temps below the dew point.

I don't offhand know the best way to fix it, other than to lower the humidity or raise the temp. Presumably increasing or decreasing the airflow would change it, but hard to say which would change it which way.

It's could be worse if the airflow through the evaporator is too high, resulting in less moisture capture there, and thus a higher dew point of the cold air from the supply. Or it could be worse if the airflow is too low, resulting in too-cold air.


As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville