25
13kW heater kits and higher, a 2-stage heat thermostat can be used to energize the W2
terminal on the blower control board upon a call for a 2nd stage of heat which will in turn
will energize the 2nd stage heater elements. The heater kit will cycle between the 1st
and 2nd stages of heat at the direction of the thermostat.
When the thermostat call for heat is satisfied or the thermostat is turned to the off posi-
tion, the W1 terminal on the blower control board is de-energized which will de-energize
the heating elements in a few seconds as the bimetallic disc in the sequencer cools. The
blower motor will be de-energized 75 seconds after the call for heat ends.
4.3.3 HEAT PUMP HEATING MODE
When the heat pump thermostat is set to “heat” mode, the “B” terminal on the outdoor
unit is energized which energizes the reversing valve and switches it to the heating posi-
tion. When the thermostat calls for heat, the G terminal on the blower control board is
energized which in turn energizes the indoor blower motor. This causes the indoor blow-
er to circulate air through the air-handler and duct system during the heating cycle. For
(-)F1T air-handlers, the Y terminal on the blower control board is also energized which
tells the blower control board to energize the heating speed on the motor instead of the
reduced CFM continuous fan speed. The heating speed on the motor is the same as the
cooling speed.
Should the room temperature continue to fall when the system is operating in the heat
pump heating mode, the thermostat energizes the W2 terminal on the blower control
board which energizes supplemental electric heat. For 13kW heater kits and larger, the
W1 and W2 pigtails can be connected together for maximum supplemental heat for 2nd
stage or wired to the W1 and W2 terminals on the thermostat separately to provide a 3rd
stage of heat as needed.
When the thermostat call for heat is satisfied, the G and Y terminals on the blower con-
trol board are de-energized. A time delay programmed into the (-)F1P blower control
board or (-)F1T motor keeps the blower motor energized for an additional 30 seconds to
extract the residual heat from the warm indoor coil.
4.3.4 SUPPLEMENTAL ELECTRIC HEAT DURING DEFROST
Supplemental electric heat during the defrost cycle can be provided by running a wire
from the purple pigtail wire (from D terminal on defrost control) on the outdoor heat
pump unit to the W1 pigtail on the air-handler. This will energize the electric heat during
the defrost cycle to prevent cold air from being discharged from the supply registers in
the home.
For the most economical operation and if cold discharge air is not a concern, do not run
the wire from the purple pigtail on the outdoor unit to the W1 pigtail on the air-handler. In
this case, supplemental heat will only be energized if the thermostat energizes the 2nd
stage of heat during the defrost cycle due to a significant drop in room temperature.
4.3.5 EMERGENCY HEAT (HEAT PUMP)
If heat pump thermostat is set to the “Emergency Heat” mode, the outdoor unit will be
prevented from operating and heat will be provided solely by the electric heater. The
electric heater elements and indoor blower motor will be energized any time there is
a call for heat with no compressor and outdoor fan operation. A jumper should be
installed between the W1 and E terminals on the thermostat sub-base so a call for
emergency heat will be transferred to the 1st stage of heat of the thermostat. The indoor
blower will cycle on and off with the electric heater elements when the thermostat fan
setting is set to the “auto” mode, although there will be a 75 second delay off period for
the blower motor after the call for heat ends.
4.3.6 THERMOSTAT FAN SETTING
If the thermostat “FAN” setting is adjusted to the “AUTO” position, the indoor blower
motor will only operate when there is a call for cooling or heating. If the setting is
adjusted to the “ON” position, the indoor blower motor will operate continuously. On
(-)F1T models, the indoor blower motor will operate at a reduced speed when there is no
call for cooling and heating to reduce power consumption and noise.
4.4 CORRECTING ELECTRIC HEAT kW FOR VOLTAGE
The actual electric heat kW varies with the supply voltage. Use the following formula to
correct the heater rated kW at voltages other than rated voltage.
Actual kW = Rated kW × (Actual Voltage
2
/ Rated Voltage
2
)
.
4.5 CALCULATING ELECTRIC HEAT CAPACITY IN BTUH
Use the following formula to convert heater kW to heating capacity in BTUH.
BTUH Capacity = kW × 3412
(Where 3412 = BTUH per kW)
