21
Short Cycle Protection
1. With the system operating in cooling mode, note the
temperature setting of the thermostat and gradually raise
the set-point temperature until the unit de-energizes.
2. Immediately lower the set point temperature of the
thermostat to its original setting and verify that the
indoor blower is energized.
3. After approximately 5 minutes, verify the compressor
and fan energize and the temperature of the discharge
air is cooler than the room temperature.
NOTE:
This is
available only for the single phase models.
System Cooling
1. Set the thermostat’s system mode to COOL and the
fan mode to AUTO. Gradually lower the thermostat
temperature setpoint below room temperature and
verify the outdoor unit and indoor blower energize.
2. Feel the air being circulated by the indoor blower and
verify that it is cooler than ambient temperature. Listen for
any unusual noises. If unusual sounds occur, determine
the source of the noise and correct as necessary.
3. Allow the cooling system to operate for several minutes
and then set the temperature selector above room
temperature. Verify the fan and compressor cycle off
with the thermostat.
NOTE:
The blower should also
stop unless fan switch is set to the ON position.
Secondary Heating
1
.
Switch the thermostat mode to emergency heat.
2. Verify that the compressor and fan de-energize. The
indoor fan will continue to run and the inducer motor
will energize. The furnace will run at high fire as wired
at the factory. If the furnace has been wired for two-
stage operation, the furnace will run at low fire.
3. Feel the air being circulated by the indoor blower and
verify that it is warmer than ambient temperature.
Listen for any unusual noises. If unusual sounds
occur, determine the source of the noise and correct
as necessary.
4. Follow the procedures given on the operating instruction
label, in this installation instructions or attached inside
the louvered control access panel.
5. Run the unit for approximately five minutes and set
the thermostat below room temperature. Verify the
shutdown sequence; steps 10 - 12 in the Operating
Sequence section (page 23)
Verifying & Adjusting Temperature Rise
Verify the temperature rise through the unit is within the
range specified on the unit data label. Temperature rises
outside the specified range could result in premature heat
exchanger failure.
1. Place thermometers in the return and supply air stream
as close to the unit as possible. The thermometer on the
supply air side must be shielded against direct radiation
from the heat exchanger to avoid false readings.
2. Adjust all registers and duct dampers to the desired
position. Run the unit for 10 to 15 minutes before
taking any temperature readings. The temperature
rise is the difference between the supply and return
air temperatures.
NOTE:
For typical duct systems, the temperature rise will
fall within the range specified on the data label (with the
blower speed at the factory recommended setting) shown
in Table 10, page 28. If the measured temperature rise falls
outside the specified range, it may be necessary to change
the blower speed. Lowering the blower speed increases
the temperature rise and a higher speed decreases the
temperature rise.
The unit is equipped with a variable speed motor. Heating
and cooling speed selection is made by changing the
switch settings on the integrated control located in the unit
control box. Refer to the Variable Speed Blower Section
(page 15) for more details.
The VSB is designed with built in delay profiles for start
up and shut down of the system. Refer to the Operating
Sequence section (page 23) for more details.
Verifying & Adjusting Firing Rate
CAUTION:
Do not re-drill the burner orifices. If the orifice
size must be changed, use only new orifices.
The firing rate must be verified for each installation to
prevent over-firing of the furnace.
The firing rate must
not exceed the rate shown on the unit data label.
To
determine the firing rate, follow the steps below:
1. Obtain the gas heating value (HHV) from the gas
supplier.
2. Shut off all other gas fired appliances.
3. Start the unit in heating mode and allow it to run for at
least 3 minutes.
4. Measure the time (in seconds) required for the gas
meter to complete one revolution.
5. Convert the time per revolution to cubic feet of gas per
hour using Table 14 (page 29).
6. Multiply the gas flow rate in cubic feet per hour by the
heating value of the gas in Btu per cubic foot to obtain
the firing rate in Btu per hour. See Example.
Example
:
• Time for 1 revolution of a gas meter with a 1 cubic
foot dial = 40 seconds.
• From Table 14, read 90 cubic feet gas per hour.
• Local heating value of the gas (obtained from gas
supplier) = 1,040 Btu per cubic foot.
• Input rate = 1,040 x 90 = 93,600 Btuh.
7. Adjust the manifold pressure if necessary. See Manifold
Pressure Adjustment instructions on page 22. For
additional information about elevations above 2,000
feet, see page 19.
