9
4- OPERATION
4.1- START-UP
Before starting up the unit, be sure to check that the following
items are in compliance:
1. The electrical installation and ventilation;
2. The blower access door is in place and the blower rail
locking screws are well tightened;
3. The blower speed adjustments for heating and air
conditioning are appropriate and in accordance with the
specifications in this manual;
4. The thermostat of the room is in heating mode and is set
higher than the ambient temperature;
5. The breakers on front panel are set on
the “ON” position
.
To start the unit, turn the main electrical switch on.
4.2- LEGACY OPERATING SEQUENCE
The blower motor is a true variable speed motor designed to
deliver constant CFM. Constant CFM is valid for systems with
total external static pressure between 0.1 and 0.8 inches water
column.
4.2.1- Continuous fan
Thermostat closes circuit R to G.
Blower runs at continuous fan airflow.
4.2.2- Cooling mode
–
single stage
If indoor temperature is above temperature set point and
humidity is below humidity set point, thermostat closes
circuits R to G, R to Y/Y2 and R to O.
NOTE: For single stage systems, do not use the Y1 terminal.
Furnace delivers single stage cooling airflow.
4.2.3- Cooling mode
–
two stage
First stage (low) cooling: Thermostat closes circuits R to G,
R to O, and R to Y1.
Furnace delivers low stage cooling airflow.
Second stage (high) cooling: Thermostat closes circuits R
to G, R to O, R to Y1 and R to Y/Y2.
Furnace delivers high stage cooling airflow.
4.2.4- Cooling mode
–
dehumidification
If indoor temperature is above temperature set point and
humidity is above humidity set point, thermostat closes
circuits R to G, R to Y/Y2 and R to O and humidistat opens
circuit R to DH.
The furnace delivers airflow which is approximately 80% of
the nominal cooling airflow to increase the latent capacity of
the system.
4.2.5- Electrical heating mode
–
modulating thermostat
The thermostat sends a heating demand in the form of a pulse
width modulated wave that varies between 5 and 100%. The
heating unit will apply this power ratio to the maximum available
power. The electrical elements will modulate to the required
power and the fan will adjust itself automatically in order to reach
the required temperature rise.
4.2.6- Heat pump heating mode
–
modulating thermostat,
outdoor unit single stage
Thermostat closes circuits R to G and R to Y/Y2.
NOTE: For single stage systems, do not use the Y1 terminal.
Furnace delivers single stage heat pump heating airflow.
4.2.7- Heat pump heating mode
–
modulating thermostat,
outdoor unit two stage
a. First stage (low) heating: Thermostat closes circuits R
to G and R to Y1.
b. Furnace delivers low stage heating airflow.
c.
Second stage (high) heating: Thermostat closes R to
G, R to Y1 and R to Y/Y2.
d. Furnace delivers high stage heating airflow.
WARNING
E
LECTRICAL SHOCK OR UNIT DAMAGE HAZARD
Failure to carefully read and follow this WARNING could
result in equipment malfunction, property damage,
personal injury and/or death.
Disconnect power to unit before removing or replacing
connectors or servicing motor. Wait at least five (5) minutes
after disconnecting power before handling.
4.3- AIRFLOW VERIFICATION
Verify the airflow by taking readings of the following points, while
the elements are in heating mode:
a. Total amperage of all the heating elements;
b. Voltage at the furnace;
c.
Supply air temperature. The point of the reading must not
be affected by radiant heat from the elements;
d. Return air temperature.
From these readings, one can arrive at an approximate
calculation of the average airflow. To do that, the following
formula should be used:
0.82 x amps. x volts
Liter/s= -------------------------
Diff. temperature ˚C
3.1 x amps. x volts
CFM = ------------------------
Diff.
temperature ˚F
4.3.1- Supply air temperature rise test
1. Operate the unit at maximum power for at least 10 minutes;
2. Measure the air temperature in the return air plenum;
3. Measure the air temperature in the largest trunk coming off
the supply air plenum, just outside the range of radiant heat
from the heat exchanger. 0.3 m (12”) from the plenum of
the main take-off is usually sufficient;
4. Calculate the temperature rise by subtracting the return air
temperature from the supply air temperature.
