TR16 HVAC Control Unit
The TR16 HVAC Control Unit works in conjunction with the Wall Display Unit to provide thermostatic
control of the HVAC system. In addition, the Control Unit can receive serial RS485 commands for remote
control of the heating/cooling setpoints and mode of the thermostat. The TR16 can also report various
status information via the serial communications network.
The TR16 Control Unit connects to the HVAC system the same as, and in place of, a standard thermostat.
It is usually mounted near the HVAC system, although it can be mounted anywhere convenient. It is
connected to the WDU by a 4 wire cable, either standard thermostat wiring or typically Cat 3/5 in new
construction.
Actual thermostatic control of the HVAC system is provided by the Control Unit. Changes in the current
temperature, setpoint, system or fan modes are sent to the Control Unit either from the WDU or via serial
commands. The Control Unit monitors this information and operates the HVAC system accordingly.
HVAC System Compatibility
The TR16 works with almost all heating and cooling systems, including standard Gas/Electric, Heat Pump,
Radiant, or Hydronic systems and with single or multi-stage systems. Compatible with single or separate
transformer heating/cooling systems (Note: one stage heat only for split heat/cool transformers).
System Type
Heating Stages
Cooling Stages
Notes
Gas
2
2
Single or split transformer
Electric
2
2
Selectable Fan with Heat
Heat Pump
3
2
Selectable Changeover with Heat or Cool
STANDARD GAS/ELECTRIC HVAC SYSTEMS OPERATION
The TR16 has typical HVAC system operating modes of Heating, Cooling and Auto changeover.
In additional to the multiple stages, the TR16 has adjustable temperature difference (
delta
) between
stages and an adjustable
deadband
between heating/cooling setpoints. These control unit variables can
be changed via network commands. The examples below are based on the default settings.
In the
HEAT
mode, the stage 1 heating will be turned on at one degree below the heating setpoint and will
turn off
at
the setpoint. In the
COOL
mode, the stage 1 cooling will be turned on at one degree above the
cooling setpoint and will turn off
at
the setpoint. This is referred to as the setpoint delta. It is default set to
1 deg but can be changed via network commands.
Second stage heating/cooling deltas are factory set at 3 degrees. This means that second stage will come
on when the delta from setpoint reaches 3 degrees. Second stage heating/cooling calls will stay on until
the first stage setpoint is satisfied.
In the
AUTO
mode, the system will maintain the heating or cooling setpoints and switch automatically from
heating mode to cooling mode as needed. There is a
deadband
between heating and cooling setpoints
that keeps the two setpoints from overlapping. This is default set to 4 degrees, but can be changed.
Setpoint Push.
If you adjust the heating setpoint to be less than 4 degrees from the cooling setpoint, the
cooling setpoint will be
pushed
to maintain the 4 degree deadband separation. Same for adjusting the
cooling setpoint, if you get within the deadband separation, the heating setpoint will be pushed.
Minimum Run Time (MRT)
. The HVAC control unit has a minimum run time that starts with
every
heating or cooling call. The HVAC system will run this minimum time even if the temperature reaches
setpoint before MRT times out. However, if the mode is set to Off, the MRT will be canceled and the
DCN: 141-00930-09 7/13/06
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