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553_D - 04/13
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A Watts Water Technologies Company
The thermostat has three humidification modes.
Mode
Operation
HM1
Stand Alone Humidifier
Humidifier operates independently of the HVAC system.
Available in all modes except off.
HM2
Humidifier with Fan
Humidifier ducted together with HVAC system. The system fan is oper-
ated whenever the humidifier is operating. This is only available when
operating a conventional heating system with a fan.
Available in all modes except off.
HM3
Humidifier with Air Heating
Humidifier ducted together with HVAC system. The air system must be
heating (heat pump, furnace, electric or hydronic fan coil) in order to
allow the humidifier to operate.
Available when heating.
The thermostat has three dehumidification modes.
Mode
Operation
DHM1
Stand Alone Dehumidifier
Dehumidifier operates independently of the HVAC system.
Available in all modes except off.
DHM2
Coil Dehumidification
A DX coil compressor is operated with the blower fan operating at its
dehumidification speed.
DHM3
HRV Dehumidification
(requires an outdoor temperature reading to be available)
The HRV is operated based upon indoor dew point and outdoor air tem-
perature. The HRV operates when the indoor dew point is 5.5°F (3.0°C)
above the outdoor temperature. The HRV is shut off when the indoor dew
point falls to 2°F (1.0°C) above the outdoor temperature.
Available in all modes except off.
DX Coil Frost Protection
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When operating a coil dehumidification system (DHM2), frost protection of the DX coil
can be provided when an optional Duct Sensor 083 is installed. In the event that the
duct air temperature nears freezing, the thermostat removes the dehumidification signal
and the cooling compressor is allowed to operate together with the fan operating at full
speed to allow the DX coil to warm up.
