© 2013
553_D - 04/13
35 of 48
A Watts Water Technologies Company
Fan Operation
Section G
The fan operates together with the air heating or cooling systems. The user can also
select to operate the fan manually by pressing the Fan button. This allows the user to
choose between Auto and On. “Auto” allows the fan to operate together with heating or
cooling but normally the fan is off. “On” forces the fan to operate continuously.
Ventilation Fan
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In order to provide ventilation to the building, the fan can also operate for additional
time beyond what is required for the heating and cooling systems. Ventilation allows the
user to select the fan to operate for a minimum percentage out of each hour. Options
are 10 to 90%, in 10% (6 minutes per hour) increments, as well as Auto and On. This
is available when the Vent Mode setting in the Setup menu is set to On.
Once Ventilation is set to On, the Fan minimum run time percentage during the and
events can be set so that the fan can operate on a schedule and/or together with scenes.
Fan Post Purge
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The fan relay includes a post purge feature that operates the fan after the heating or
cooling system has shut off. When a duct temperature sensor is installed the length
of post purge is based on the air duct temperature and the Heat Purge or Cool Purge
temperature settings. When there is no duct temperature sensor installed, the length
of post purge is based upon the Heat Purge and Cool Purge time settings.
Relative Humidity Operation
Section H
Relative Humidity (RH) is controlled by maintaining the Minimum Humidity using
humidification and by maintaining Maximum Humidity using dehumidification. The RH
is maintained within a 5% differential. The differential is applied above the minimum
setpoint, and applied below the maximum setpoint.
To avoid condensation on windows, the minimum relative humidity setting can be
changed according to the following outdoor temperatures.
Outdoor Temperature
-10°F (-23°C) 0°F (-18°C)
10°F (-12°C)
20°F (-7°C)
30°F (-1°C)
Suggested RH Min
20%
25%
30%
35%
35%
RH is affected by changes in the ambient air temperature. When using a programmable
schedule, the thermostat calculates the relative humidity setpoint with respect to the Set
Heat Room setting when in heat mode, the Set Cool Room when in cool mode,
and the average between Set Heat Room and Set Cool Room when in auto mode.
This may result in changes in displayed RH when the mode is changed.
When the mode is set to off, the humidification and dehumidification systems do not
operate.
