Filter
Top Products
3
HUMIDIFIER TYPES
Bypass Humidifier
This humidifier takes heated air from the plenum, draws it through a water pad and deposits the moist
air in the return. The most common operation works with heat only. If the furnace is on only for a
short time, the humidified air cannot be distributed evenly through the house. In fact, the heat from
the furnace will remove moisture.
Power Humidifier
This humidifier takes air (room temperature or heated) from the plenum, draws it through a water pad
and forces the humidified air back into the plenum. This application allows more moisture to be distrib-
uted throughout the house. Some power humidifiers have transformers, and if this were the case, an
isolation relay would have to be installed. An isolation or heavy-duty relay is also needed if the current
draw of the power humidifier exceeds the 1 amp rating of the thermostat humidity relay contacts.
Mist or Steam Humidifier
This humidifier takes water or steam and sprays it into the plenum. Setting up this application is
critical, as the water may not fully evaporate.
DEHUMIDIFICATION
The D output is energized (24VAC) on no call for dehumidification.
When dehumidification is required, then D becomes deactivated (0 VAC). This is reverse logic.
Some control boards on furnaces (that have variable speed motors) have the D connection and look
for the voltage to maintain normal fan speed.
If the control board sees “0” VAC, then the control board automatically lowers the fan speed.
The 5-minute compressor short cycle time still applies in all modes of dehumidification.
COOLING
On a call for cooling, the thermostat will activate Y1 above the setpoint, and turn off below the setpoint
for a 1° differential (default). The differential is user adjustable (0.5, 1, 2, or 3°F) in 0.5° increments.
For multistage units, the second stage cooling (Y2) follows the on-off 2nd stage temperature
differentials. The default time (adjustable) is ten minutes.
MANUAL DEHUMIDIFICATION WITH COOLING
Dehumidification can become active only: 1) after the temperature rises to cause a cooling demand,
and, 2) the RH is still 2% above RH setpoint.
If room RH is 2% above the RH setpoint and cooling turns on, then the D terminal will be active or
de-energized (0 VAC). If dehumidification is successful before cooling requirements are met, then D
will switch to inactive (24 VAC present) while cooling continues.
The Y1, and D terminals will revert to their original state when room temperature has been reached.
The G terminal will remain on until the residual time off delay has timed out. (User selectable 0, 30, 60
or 90 seconds. Factory default is 30 seconds.)