How to lower humidity? Is my system at fault?

[jo8243]

The humidity in my house stays between 50-60% during the summer with the thermostat set to 73.

Some details: The house is located in north Alabama. It is 5 years old with a Bryant 3.5 ton heat pump. The house is 2300 sq ft. It is one story, on a concrete slab. There is one return duct, which I believe is 18" or 24" (need to check). The return grill is 24"x30". I run a 3M filterete electrostatic filter.

I'd like the humidity to be in the 40-45% range, which I understand is about where it should be. Is that reasonable? What could be wrong with the system or install to cause the humidity to be higher?

If I hire an a/c company to come look at it, what tests should they perform and what problems should they look for?

Thanks

[nina]

try with a MERV 8 or less rated filter. (I think the 3M are rated at MERV 13 or some other high value)

ensure coil is clean. thermo really at 73F? have you verified this value and the RH% value with an independent tool (ie. radio shack)?

[tigerdunes]

jo8243

Is your heat pump in AC mode maintaining your thermostat setpoint of 73 deg? What is your normal cycle runtime of your system?

I would ask service dealer to measure split temp between return air and supply air. It should be in a range of 15 to 20 deg difference.

I would check the cleanliness of your evap coil. I assume your evap coil has a TXV. THis needs to be checked.

I would check ductwork both supply and return for any obvious leakages.

My opinion.

[BaldLoonie]

In a steamy climate, you may never run 40-45% without an add-on dehumidifier. I don't see lower 50s as too bad. That's what mine runs. I have a small tight house, TXV coil and slow ramp up on the blower. I do not use the dehumidify on demand capability of my variable speed blower.

Don't run the fan constantly, put in automatic to cycle with the cooling!

[thorton]

Originally posted by BaldLoonie
In a steamy climate, you may never run 40-45% without an add-on dehumidifier. I don't see lower 50s as too bad. That's what mine runs. I have a small tight house, TXV coil and slow ramp up on the blower. I do not use the dehumidify on demand capability of my variable speed blower.

Don't run the fan constantly, put in automatic to cycle with the cooling!



Sounds like great advice you gave, baldloonie! 50% to 55% RH at 73 degree setpoint is pretty good in my opinion, too. I have VS blower with dehumidification set point at 55% and I don't let the fan run constantly, either.

thorton
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