High humidity level with air conditioning running

[Lisa J]

Hi everyone- I wrote about a month ago about a noisy roof fan at my apartment complex. They replaced the fan so that problem was solved. Now I have a new problem.

I live in a hot humid area and it was around 93 degrees yesterday with around 55% humidity. Normally my apartment central air conditioning works great and I like it around 68 degrees. Over the past few days it has only cooled to around 70-72 degrees with the thermostat set low and the fan on medium. I have two humidity guages and they are reading at around 85% humidity, which makes my apartment warm and muggy. This has never happened before. If the humidity is only 55% outside, why is it 85% in my closed apartment? I don't have any water leaks and I am not running water.

Thanks to all of you who respond!

[coolwhip]

68 is alot to ask from any a/c unit and Im sure design specs for your area dont call for that.

The a/c unit may be oversized giving you short run times and not enough run time to remove the humidity.

[RoBoTeq]

If you were in the Mid-Atlantic area, their was no way to keep the humidity down the last couple of weeks. Lots of rain and not much heat makes for humid indoor conditions.

In your case, 55% humidity in 93 degree air cooled to 73 degrees is nearly 100% humidity. You are reaching dewpoint temperature and may be seeing moisture forming on windows.

Condensate removal line may be clogged.

[Lisa J]

Thanks Coolwhip- ususally the a/c is so cooling it is like a meat locker in my apartment- that's why this high humidity is so odd. Thanks for your info Roboteq- we have had a lot of rain around here but not so much lately, and it has not affected the a/c before. They think the new roof fan may not be ventilating the bathroom and I have a feeling that will turn out to be the problem. I just hope they can get it fixed fast for the long weekend. I'll let you know. Thanks again!

[RoBoTeq]

If the new roof fan is pulling conditioned air from your apartment, then unconditioned, 55% humidity at 93 degree outside air is being pulled into your apartment from cracks around doors and windows and anywhere else the building shell is not sealed. This can indeed cause a problem.

Do you by any chance have a vented fireplace?

[lions_lair]

A common mistake is leaving the fan in the wrong mode at the thermostat...it should be set to auto in a humid area.

[flanders]

Over the past few days it has only cooled to around 70-72 degrees with the thermostat set low and the fan on medium.

Is this the roof fan or the AC fan?

[Lisa J]

Thanks to all of you who have replied.

The central air conditioning thermostat fan is set at medium (choices are low, medium, high). I can't control the roof fan. I am pretty sure that the problem is because the ventilation fan airflow is very low and it used to be much stronger. This was confirmed by the apartment maintenance guy.

I don't have a fireplace and I've lived in the apartment for over 10 years. The windows are new (replaced 3 years ago) and have a very good seal. I've always had frosty cold a/c and that is why this is so strange to have the high humidity. The problem started 3 weeks ago when the roof fan was replaced because it was so noisy. They are having an "expert" come out to assist the apartment maintenance guy on Tuesday. I hope these guys can get the problem solved. Even though fans are keeping the air circulating, there is a damp feeling in my apartment.

Thanks guys and have a safe and insane Memorial Day weekend!

[teddy bear]

Thanks to all of you who have replied.

The central air conditioning thermostat fan is set at medium (choices are low, medium, high). I can't control the roof fan. I am pretty sure that the problem is because the ventilation fan airflow is very low and it used to be much stronger. This was confirmed by the apartment maintenance guy.

I don't have a fireplace and I've lived in the apartment for over 10 years. The windows are new (replaced 3 years ago) and have a very good seal. I've always had frosty cold a/c and that is why this is so strange to have the high humidity. The problem started 3 weeks ago when the roof fan was replaced because it was so noisy. They are having an "expert" come out to assist the apartment maintenance guy on Tuesday. I hope these guys can get the problem solved. Even though fans are keeping the air circulating, there is a damp feeling in my apartment.

Thanks guys and have a safe and insane Memorial Day weekend!

Sounds like you a/c fan is in the med speed "on" mode. It should be in the "auto" mode. This means that the a/c fan does not blow when the a/c is not cooling. Also measure the supply temp of the cold air. Should be 20^F colder than the room air temperature. Ok
Regards TB

[RoBoTeq]

A common mistake is leaving the fan in the wrong mode at the thermostat...it should be set to auto in a humid area.

This is not a hard set rule. There are many situations where variable speed blowers can be set up to operate continuously in humid areas.