System information

DCN: 141-01070-03 TR40 Thermostat Manual 25
TR40 CONTROL UNIT
STANDARD HEATING/COOLING HVAC SYSTEMS OPERATION
In the HEAT mode, the heating system will be turned on at one deg below the setpoint and will turn off at the
setpoint. In the COOL mode, the cooling system will be turned on at one deg above the setpoint and will turn
off at the setpoint. In the AUTO mode, the current heating or cooling operating mode will operate as usual
with the one deg setpoint control. In order for the system to change operating mode from heating to cooling,
the temperature must rise two deg above the setpoint. On subsequent calls after a change over has
occurred, the system will operate normally with the one deg setpoint control. This changeover difference of
two deg on the first call helps to prevent the system from overshooting and oscillating between heating and
cooling. Changes from cooling to heating works similarly, with the two deg changeover difference being two
deg below the setpoint.
STANDARD GAS/ELECTRIC MODE SELECTION. To set the Control Unit for standard GAS/ELECTRIC
operation, leave the dipswitch SW1-1 set to OFF (default setting).
FAN MODE SELECTION. Normally, GAS heating systems DO NOT require fan calls along with the heat
call due to thermoswitch fan operation in the furnace and dipswitch SW1-2 should be set to OFF (default
setting) for standard fan operation. Electric and hydronic heating systems generally DO require that a fan call
be generated along with the heat call and dipswitch SW1-2 should be set to ON position for fan with heat
operation. Be sure to check your HVAC system’s requirements.
HEAT PUMP HVAC SYSTEMS OPERATION
The heat pump system mode works similarly to the standard systems. Normal heating/cooling calls and
auto changeover function the same as standard systems. The major difference is the second stage heat.
Heat pump systems use the compressor for the primary heating/cooling source. During conditions of high
heating requirements, additional heat stages, usually electric strip heaters, may be used. These second
stages of heating will be turned on when the current temperature falls four deg below the current setpoint and
will turn off when the difference is reduced to two deg below the current setpoint.
HEAT PUMP MODE SELECTION. To set the Control Unit for Heat Pump operation, set the STD/HP
dipswitch SW1-1 to ON.
FAN MODE SELECTION. For normal Heat Pump Operation, set the FAN/HEAT selection dipswitch, SW1-2,
to OFF for standard fan operation,
CHANGE OVER SELECTION. Heat pump systems change from heating to cooling by reversing the
direction of Freon flow in the system. This change over is controlled by the change over (sometimes referred
to as reversing valve) output from the Control Unit. Most heat pump systems are designed to work normally
in the heating mode and require a change over output for cooling. Set SW1-3 to OFF (default) for this type
system. Check your HVAC system requirements for correct settings. If your system requires change over
with heating, set SW1-3 to ON. After the change over relay output is first activated, it will stay on
continuously even when there is no call until it is turned off by changing to the opposite mode. This prevents
continuously cycling of the reversing valve with each call as a system generally stays in either the heating or
cooling mode for extended periods.
REMOTE OPERATION
The TR40 has a serial communications interface that allows remote commands generated by other systems
to be received by the TR36. These remote commands can change the setpoint, temperature and mode of the
system or may request current status of temperature, setpoint and mode.
REMOTE COMMANDS
Refer to the RCS Serial Protocol document, DCN:150-00225, for detailed information on remote commands to
communicate with the TR40 thermostat.