14
Sequence of operation
Start-up
The random time delay prevents any unit operation for 10
to 60 seconds after initial application of power to the unit.
The concurrent time delay prevents compressor and
condenser fan operation for 3 minutes. This time delay
also functions any time there is an interruption in the call
for compressor operation.
NOTE: Additional time delays may be programmed into
certain electronic thermostats.
When the thermostat fan switch is set to ON, the evap-
orator blower is energized.
NOTE: In either cooling or heating mode, if the thermostat
is calling for operation of the compressor during the
3-minute time delay, the evaporator blower will not ener-
gize with the fan switch ON.
Cooling
On a call for cooling, the condenser fan and evaporator
blower are energized simultaneously. After 10 seconds the
compressor will energize. All three functions are disabled if
the 3-minute time delay is active. The unit will operate until
the thermostat is satisfied.
When the thermostat is satisfied, the compressor and
condenser fan will deenergize and the evaporator blower
will continue to operate for an additional 45 seconds.
A temperature sensor (normally open) is installed on the
suction line to interrupt the operation of the unit (in cooling
mode only) in the event of limited airflow across the evap-
orator coil.
An outdoor ambient temperature sensor (normally
open) is installed, which disables compressor and condens-
er fan operation when the outdoor temperature is below
40 F.
If the compressor is operating when the switch closes,
the compressor will be allowed to operate until the thermo-
stat is satisfied.
If the switch is closed (ambient temperature is less than
40 F), when the thermostat calls for cooling, then the com-
pressor will not be allowed to operate and the indoor blow-
er will operate until the thermostat is satisfied.
Heating (electric and hot water heat)
On a call for heat, for electric heat and hot water heat
units, the evaporator blower and the first bank of heating
elements are energized and function until the thermostat is
satisfied.
NOTE: Units with 5 kW or less of electric heat have only
one bank of elements.
After 15 seconds, the second bank of heating elements
is energized and functions until the thermostat is satisfied.
Each bank of heating elements is equipped with a temper-
ature limit, which will interrupt power to the heating ele-
ment in the event of excessive temperature.
Heating (heat pump units)
On a call for heating, the condenser fan and evaporator
blower are energized simultaneously and after 10 seconds
the compressor will energize.
NOTE: All three functions are disabled if the 3-minute time
delay is active.
The unit will operate until the thermostat is satisfied.
Any time that power is applied to the unit and the ther-
mostat is set to Heat or Auto, the reversing valve will be
energized and in the heating position. If the room temper-
ature is more than 2 degrees lower than the thermostat set
point, then the electric heating elements will be energized
and will operate until the difference between the set point
and room temperature is less than 2 degrees.
NOTE: Any time that the thermostat calls for electric heat,
the compressor and condenser fan will be locked out and
will not operate until the electric heat is no longer called
for. The 3-minute time delay is functional in this mode and
will override the re-start of the compressor if it is active.
An outdoor ambient temperature sensor (normally
open) is installed, which limits compressor and condenser
fan operation when the outdoor temperature is below
40 F.
If the compressor is operating when the switch closes,
the compressor will be allowed to operate until the thermo-
stat is satisfied.
If the switch is closed (ambient temperature less than
40 F) when the thermostat calls for heat (Y1/W1), the
compressor will not be allowed to operate and the electric
heating elements will operate.
An outdoor coil temperature sensor (normally closed) is
installed which is designed to interrupt compressor and
condenser fan operation if the line temperature gets into a
freeze up condition. Any time that this switch is activated
and there is a thermostat call for heat, the unit will auto-
matically switch to electric heat operation until the switch
resets. A 6-hour time delay is set whenever the sensor in-
terrupts the compressor operation. During this time delay
any call for heat will bring on the electric heating elements.
Thermostat specifications
Fan operation —
Press the FAN button to select fan
mode.
Auto mode — Fan will operate for 3 minutes minimum (tri-
al fan period) to sample air temperature. If heating or cool-
ing is not required, fan will turn off. Fan wlll remain inac-
tive until heating or cooling become active.
On mode — Maintains constant fan operation.
Economy mode — Automatic economy function. Room
temperature will be maintained between the economy heat
(EH) activation temperature and the economy cool (EC) ac-
tivation temperature. The LCD wlll appear blank. When
room temperature rises 2 F above the EC activation tem-
perature, the LCD will display the cool value and cooling
symbol and activate cooling with fan.
When room temperature falls 2 F below the EH activa-
tion temperature, the LCD will display heat value and heat-
ing symbol, and activate heating with fan.
Temperature selection —
Press UP or DOWN buttons
to set temperature.
Controls