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RT-PRC031-EN 15
Controls Constant Volume (CV) Only
Electric Heating
The individual stages of electric heat
will be sequenced on the zone
demand. The number of available
stages will depend on the unit size
and heat capacity selected.
Hot Water or Steam Heating
Upon a call for heat, the UCM will
send a varying voltage signal to the
valve actuator. The valve will
modulate to meet building demand
as indicated by the voltage signal.
When heating is satisfied, the valve
will modulate closed. A temperature
sensor is located on the coldest
section of the coil. When it senses an
impending freeze condition, a signal
is sent to the hydronic valve to drive
it full open. If the supply fan is on, or
if the outside air damper is open
when this freezing condition is
sensed, the supply fan is turned off
and the fresh air damper is closed.
Supply Air Tempering
For staged gas and electric heat units
in the occupied Heating mode but
not actively heating, if the supply air
temperature drops to 10°F below the
Occupied zone heating temperature
setpoint, one stage of heat will be
brought on to maintain a minimum
supply air temperature. The heat
stage is turned off if the supply air
temperature rises to 10°F above the
Occupied zone heating temperature
setpoint.
On units with hot water or steam
heating, if the supply air temperature
drops below 48°F, the heating valve
is modulated to maintain 50°F supply
air temperature with a 4°F deadband.
Auto Changeover
When the System Mode is “Auto,” the
mode will change to cooling or
heating as necessary to satisfy the
zone cooling and heating setpoints.
The zone cooling and heating
setpoints can be as close as 2°F
apart.
Unoccupied Zone
Temperature Control
Cooling and Heating
Cooling and/or heating modes can be
selected to maintain Unoccupied
zone temperature setpoints. For
Unoccupied periods, heating,
economizer operation or primary
cooling operation can be selectively
locked out at the Human Interface
Panels.