© 2013
553_D - 04/13
31 of 48
A Watts Water Technologies Company
Sequence of Operation
Heat and Cool Applications
Section A
The 553 can operate in several different combinations of conventional and heat pump
applications. Supported conventional heating applications are:
Application
RH% Options
1 Heat / 1 Cool / 1 Fan / Relative Humidity
Humidification Modes 1, 2, 3
Dehumidification Modes 1, 2, 3
2 Heat / 1 Fan / Humidification
Humidification Modes 1, 2, 3
Dehumidification not possible
2 Heat / 1 Cool / 1 Fan
None
Supported heat pump applications are:
Application
RH% Options
1 Radiant Floor Heat / 1 Heat Pump / 1 Fan
None
1 Radiant Floor Heat / 1 Heat Pump / Relative Humidity Humidification Modes 1 or 3
Dehumidification Modes 1, 2, 3
1 Radiant Floor Heat / 1 Heat Pump / Backup Heat
None
Heating Operation
Section B
Set Heat Temperature
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When using only a room temperature sensor, the thermostat operates the heating
system to maintain the Set Heat Room temperature.
Floor Heating
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When using both a room and a floor temperature sensor, the thermostat always maintains
the Floor Minimum temperature, even when the air temperature is satisfied. When the
air temperature is below the Set Heat Room temperature, the thermostat operates the
heating system to maintain the Set Heat Room temperature. The floor is never heated
above the Floor Maximum setting in order to protect the floor covering. Suggested
Floor Maximum settings are 90°F (32°C) for tile, stone, or concrete floors and 85°F
(29°C) for wood floors.
Radiant Floor Baseload
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When the terminal unit is selected to be a Hydronic Radiant Floor (HRF1 or HRF2)
and no floor temperature sensor is installed, the thermostat has an option to provide
baseload heating. This allows the radiant floor to be heated even though the room air
temperature is satisfied. This is useful in areas where a radiant floor heating zone is
overlapped by an air heating system. The radiant floor heating is overwhelmed by the
quick heat up rate of the air heating system, resulting in a radiant floor heating zone
that rarely turns on. The radiant baseload option allows the radiant floor to counteract
the air heating system by heating the floor at a reduced output even when the room air
temperature is satisfied. This is also useful in areas that experience large solar gains
through windows. The radiant baseload is automatically shut off in the summer by the
warm weather shut down feature.
