Bryant's Thermidistat -- how does auto-humidity work?

[dunburn]

I just had the Bryant thermidistat installed. Seems to be working well.

I am looking for help on how the auto-humidity works on the Bryant Thermidistat (programmable). Not buttons and how to turn it on etc, rather how the thermidistat calculates the decrease in indoor humidity relative to the outdoor temperature. That is to say, what are the temperature set points and humidity set points that the thermidistat uses when it switches automatically?

The manual says the humidity will drop when certain outside temperature is reached, but I have no idea what humidity is associated with what outdoor temperature.

Any help in this regard?

Steve

[jared]

I love my thermidistat, but have no humidifier...no need in my area at all.

Here's an answer direct from the manual. "When selected, the set point (humidity) is automatically reduced by 1 percent for every drop of 2*F in outdoor temperature between 50*F and 0*F. The setpoint may be changed at anytime and it will continue to track outdoor temperature from the new setpoint and current outdoor temperature. The adjusted set point range is still limited to between 10 and 45 percent relative humidity. To use this feature an outdoor temperature sensor MUST be attached. If not, an E3 error message will be displayed.

Hope I helped

[dunburn]

Thanks -- I have that in the manual as well. The challenge is that it really is not clear how the relationship between the outside temperature and indoor humidity is correlated.

let me explain.

If I set my set-point as 35% and the outside temperature is 2C, then will the humidity decrease in the mentioned incremets based on that set point? For instance, if the temerpature tomorrow is -5C, then the call for huidity would be 28% and so on...

If that is the case, my set point today (Dec 1) should then be the same same as my outside humidity which was close to 45%.

Or, is the set point your desired humidity, and then the humidity, based on factory-setttings, would decrease from that point only depending on the outside temperature? That is to say 35% at -15C, then at -20 it is 35%, then at -25C, it would decrease to 28% and so on....

(note: my temperature calculations are not accurate here).

Does that make sense?

[airworx]

it is based on an outdoor reset, just like a boiler that has out door reset. on a boiler you dont need 180 degree water temp at say 60 degrees so the reset adjust the temperture set point to 120 degrees then when the temp drops to 30 degrees it raises the set point to 170 degrees automatically. in the same way at 20 degrees the thermidistat adjusts the setpoint.
also if you do not have a veriable speed furnace or airhandler the thermidistat will not work in the dehumidification mode.

[dunburn]

Thanks that helps me understand that it switches automatically. But, it still leaves me wondering -- what is the purpose for user establishing / entering a set-point then?

And no -- I do not have a variable speed furnace (unfortunately) so dehumidifaction won't work on my furnace :-(

[dash]

Originally posted by dunburn
Thanks that helps me understand that it switches automatically. But, it still leaves me wondering -- what is the purpose for user establishing / entering a set-point then?

And no -- I do not have a variable speed furnace (unfortunately) so dehumidifaction won't work on my furnace :-(

Dehumidification can work on a standard motor,if the duct system and fan speeds will allow.


On a dehumidification call the fan runs at a lower speed,say around 320 to 350 per ton,this needs to be setup by a Pro that can check the ESP and understands the fan chart to insure adequate cfms .