Air group operation, Dx coil frost protection – tekmar 553 Thermostat Installation User Manual

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553_D - 09/14

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A Watts Water Technologies Company

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.

Air Group Operation

Section I

In order to prevent heating and cooling at the same time, this thermostat can operate
together with other thermostats on a tekmarNet

system to form an air group. On older

model thermostats the air group functionality was previously described as a cool group.
In an air group, one thermostat is assigned as the air group master. The air group master
operates both the air heating and cooling equipment for the group. The 553 can be
set to be a master or a member of the air group. When operating as a air group, the
air temperature readings of all the air group member thermostats are communicated
to the air group master thermostat and an average temperature is determined. When
the air group master is in cooling operation, the air group member thermostats do not
operate the heating system for air heating.
When operating a heat pump, the 553 also has the ability to prevent air group member
thermostats from heating while the outdoor temperature is between the Warm Weather
Shut Down (WWSD) and the Radiant Floor WWSD (W Heat WWSD) setting. This allows
the air system heat pump, fan coil or furnace to heat the building during mild outdoor
weather and avoids heating up the radiant floor slab.
If the Set Heat Room temperature is adjusted while the air group is cooling, COOL is
flashed on the display to alert the user that the air group cooling system is presently
on and heating is not available. Once the cooling system shuts off, heating is available
if required.

Air Group

tekmarNet

Communication

Member

Master