Indoor humidity control

[bluetooth751]

Went to a customers home today to add some ductwork into there new sun room. While there I checked the Thermidistat settings the indoor humidity was 68%. Humidity was set at 55%. Home owner did not complain, but the high humidity level concerned me. Equipment is a Bryant variable speed fan coil with 2-speed heatpump.

My question is what are your opinions on humidity control during temperant seasons? Having a variable speed fan coil that isn't on will not control the humidity here in South Louisiana or anywhere for that matter.

What are you guys using? What are some options?

Design conditions are 93 ODT, 78% relative humidity summer. Winter design is 35 ODT.

[teddy bear]

This is a common occurance with all a/c based "humidity control" concepts. The a/c is unable to respond the "high humidity" if there are minimum temperature lockouts. Removing the lock-out limits causes overcooling without humidity control. A high eff. whole house dehumidifier is the solution to this. The dehumidifier easily maintains 50% RH without any a/c operation. This also allows over-sizing the a/c or maintaining a high indoor air temperature. With basements, crawlspaces, and slab-on grade home, maintaining <50%RH is critical to control mold and dust mites on all of the indoor surfaces. Using 100 pints/day of dehumidification capacity with 2,500 sq.ft. of living surface provides the moisture removal required deal with ASHRAE recommended fresh air ventilation. Check out most eff. Ultra-Aire APD and other dehumidifying devices.

[cxagent]

Originally posted by bluetooth751
Went to a customers home today to add some ductwork into there new sun room. While there I checked the Thermidistat settings the indoor humidity was 68%. Humidity was set at 55%. Home owner did not complain, but the high humidity level concerned me. Equipment is a Bryant variable speed fan coil with 2-speed heatpump.

My question is what are your opinions on humidity control during temperant seasons? Having a variable speed fan coil that isn't on will not control the humidity here in South Louisiana or anywhere for that matter.


That VS HP system should be able to control the humidity better than that. The Thermidistat should be reprogrammed to bring on the cooling and one stage of the heat strips to control the humidity even when there is no call for cooling. If you check the Thermidistat instructions it has several settings for 'super dehumidify' and 'comfort heat pump' (I think).

Teddy is right about the whole house dehumidifier. However, unless there is something major wrong with the house the VS HP with Thermidistat should be able to control the RH.