Humidity is too high as room temp to cold

gstarnycJuly 7, 2012

Somewhat perplexed here. My central a/c system (two zones) is working and I have no issue getting the rooms to be very cold. I prefer rooms not too cold. (i.e. 74 degree is the target). My issue is that I continue to have very humid conditions. I purchase a humidity monitoring devise to get a actual read. The room temperature continues to drop to 70 and my RH sits between 60 - 70%.

I think wow it must be humid outside and go check accuweather and see it 89 degrees and 43% humidity.

I've read slow down the air flow to remove more humidity. Tried that for 24 hours with absolutely no change in humidity.

any advise???

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May be over sized AC.

    Bookmark   July 7, 2012 at 11:28AM
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Usually the result of an oversize system.

Residential humidity control is more of a side benefit of the cooling system (it is rarely a control input based on a humidistat).

An oversize cooling unit will not run very long to meet the temperature setting, and so less moisture is removed form the air.

The result is cold and clammy.

One thing that might help is to make sure the circulating fan is on 'AUTO' and NOT the 'ON' setting on the thermostat.

    Bookmark   July 7, 2012 at 12:11PM
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what brickeye said.
if fan is set to auto it will circulate the
condensation on the coil back into the house.

if you slow the fan speed it will dehumidify more,
if your unit allows this.

also if you put a stand alone dehumidifier
in the house? locating it centrally would
be best, and as humidity is removed you would
have to empty out the bucket.
but it would remove humidity and make
a world of difference in comfort.

do you use stove vent when cooking
and bath fans when bathing?
not venting the added humidity out
contributes to the RH inside the house.

best of luck.

    Bookmark   July 7, 2012 at 12:28PM
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I was hoping that the unit was not oversized for the loft. It's a new loft conversion in NYC and I was having trouble believing that the developer would not have consulted with the correct HVAC engineers to get these units sized correctly. (They replaced every other mechanical system in the building) including moving elevator shafts and stairwells. In previous summers I had not noticed this cold clammy feeling.

Spent the past few days reading about coil temp/air flow - fan speed. I found my coil temp was down to 47 degree. (I happen to have an infrared thermometer) I decided to purchase some non rinse coil cleaner and some pan tablets. This has helped tremendously. Within hours my rh went from 65% to 55%. At this point, I think the problem was related to some kind of dirt in condensation coils preventing the max condensation. I might even do a second application in a few days.

Thanks all for the advise..

Found great article below:

    Bookmark   July 8, 2012 at 4:02PM
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"I decided to purchase some non rinse coil cleaner and some pan tablets."

Rinse it anyway.

Is there a filter on the return?

    Bookmark   July 9, 2012 at 10:08AM
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"Is there a filter on the return?"

Add to that, are there leaks in the return ducting or around the filter?

    Bookmark   July 10, 2012 at 4:48PM
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