Humidity control thermostats

[king0518]

With Carrier equipment or others as well, is a humidity t-stat effective with base equipment and non variable speed air handlers, or do you have to have a variable speed to start to have this ability?

[BaldLoonie]

Pretty much need variable speed or possibly X13 like motors. With PSC, may be able to be done with a relay or 2 but not just a simple terminal.

[teddy bear]

With Carrier equipment or others as well, is a humidity t-stat effective with base equipment and non variable speed air handlers, or do you have to have a variable speed to start to have this ability?

Currently most do not understand the how a/cs can control humidity house. The a/c's basic setup should include adjusting the air flow of the blower to allow the a/c coil to be cold enough to provide <50%RH after a typical cooling cycle. Until the a/c coil/pan moves moisture down the drain, long term dehumidification does not occur. Any moisture left in the coil/pan will evaporate back into the home during the following off cycle. Most coil/pans retain about 1 lb. of moisture per ton of a/c. 1 lb. of moisture evaporating back into a home raises 900 sqqft. of home 10%RH. As a result, drying the home to 40%RH at the of a typical home.
The limitation of t-stat with dehumidification is limit mainly to over-cooling the home by 3^F. In mid range cooling loads there are benefits that improve dehumidification.
But the idea that this type of control will provide dehumidification throughout typical cooling cycles is a mith.
When outdoor dew points are 60-70^F and there is low/no cooling loads, reheat or dehumidification are the only reliable remedies that provide <50%RH on a continuous bases. 100 cfm of 70^F, 65^F dew point fresh air plus 4 occupants in a home is 2 lb. per hour dehumidification load.
Homes with normal occupancy and recommended fresh air change rates have a 1-3 lbs. per hour of dehumidification load without any cooling load.
If you believe the claims, you led to expect <50%RH. A good house ventilating dehumidifier will maintain <50%RH and provide adequate fresh air ventilation when occupied with or without a cooling load.
Regards TB
Regards TB

[motoguy128]

Pretty much need variable speed or possibly X13 like motors. With PSC, may be able to be done with a relay or 2 but not just a simple terminal.

+1.

That being sai,d a good starting point might also be looking at hte existing equipment and make sure it's installed correctly, charged correctly and hte airflow is set correctly for your size unit.

FOr example, if you have a 4 ton blower like on a 100k BTU furnace or a 3 ton blower on a 60k BTU furnace, the default speed conenction is high speed. Unless you have undersized ductwork, you may not need high speed if you have a smaller AC tha nthe blwoer capacity. SO if the 100k BTU furnace has a 3 ton AC installed or the 60k BTU furnace has a 2 ton AC installed, you may be able ot slow the fan speed and remove more moisture as well as operate quieter and more effcient (in humid climates).

But a service tech would need to measure the static pressure (amount of resitance to airflow in the system) to determine proper airflow using the blower fan curve listed in the installation manual.

[isuredo]

what are you meaning?, a tstat that controls humidity and using base equipment is useable....all your doiing is getting rid of the humidistat...although according to Dri Steam the best place for a humidistat is in the return...

[second opinion]

This would be the ideal location, allowing for the mixed return air from throughout the living space to be measured.


Should have qouted "isuredo"

[skippedover]

To the OP; are you referring to heating, cooling or dual heating/cooling equipment? Are you asking about HUMIDIFYING the air or DEHUMIDIFYING the air? This thread seems to be going in two directions at once, absent some direction from the OP as to the meaning of his/her question.