5750149-UIM-D-1219
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Johnson Controls Ducted Systems
Continuous Fan Airflow Settings
The default blower speed for continuous fan operation is L (Low) speed.
This furnace may be operated in continuous fan mode by setting the
wall thermostat FAN switch to ON. To select the desired continuous fan
airflow, set the FAN SPEED jumper on the control board to the desired
position. There are three options:
1.
With the FAN SPEED jumper in the “H” position the blower will run
during continuous fan operation at 100% of the selected high stage
cooling speed.
2.
With the FAN SPEED jumper in the “M” position the blower will run
during continuous fan operation at 70% of the selected high stage
cooling speed.
3.
With the FAN SPEED jumper in the “L” position the blower will run
during continuous fan operation at 40% of the selected high stage
cooling speed.
The default position is with the FAN SPEED jumper in the “L” position.
In certain circumstances, it may be necessary to move the continuous
fan speed to a different speed tap. However, doing so is not recom-
mended since it will result in higher than normal electrical energy usage
and higher than normal electric utility bills.
Gas Heating Airflow Setting
The default heating blower speed is shown in Table 18.
This unit is equipped with an electronically commutated (ECM) blower
motor. The motor and blower are capable of delivering airflow over a
wide range of operating conditions.
The desired heating airflow may be selected by placing the HEAT
jumper on the control board in the desired position A, B, C or D. The “A”
position will give the highest airflow and the “D” position gives the low-
est. Consult the blower airflow tables in this manual for the expected
airflow at each speed setting. The heating blower speed is set at the
factory to the default blower speed, which is the blower speed that will
deliver the correct airflow for proper heating operation in most applica-
tions. The default heating blower speed for each model is shown in
Table 18. Use of a heating speed other than the default heating blower
speed may result in reduced energy efficiency and higher electric utility
bills.
In certain circumstances, it may be necessary to move the heating
blower speed to a different motor speed tap. Not all motor heating
speeds are appropriate for gas heating operation for all models and all
applications. The use of heating airflow on a speed other than the
default speed will result in diminished heating performance and may
cause the furnace temperature limit controls to shut down the furnace.
Measurement of Temperature Rise
After about ten minutes of operation, determine the furnace tempera-
ture rise. Measure the temperature of both the return air and the heated
air in the ducts, about six feet (1.83 m) from the furnace where they will
not be affected by radiant heat. Increase the blower speed to decrease
the temperature rise; decrease the blower speed to increase the rise.
ADJUSTMENT OF FAN CONTROL SETTINGS
This furnace is equipped with a time-on/time-off heating fan control. The
fan on delay is fixed at 30 seconds. The fan off delay has 4 settings (60,
90, 120 and 180 seconds). The fan off delay is factory set to 120 sec-
onds. The fan-off setting must be long enough to adequately cool the
furnace, but not so long that cold air is blown into the heated space.
The fan-off timing may be adjusted by positioning the jumper on two of
the four pins as shown in Figure 25.
TAKING A FLUE GAS SAMPLE
If it becomes necessary to obtain a flue gas sample for analysis, it is
permissible to drill a small hole in the plastic flue pipe for a sample
probe, provided that the vent piping is PVC and the hole is properly
sealed afterwards. If using a polypropylene vent system, the vent sys-
tems manufacturer test port fitting must be used. DONOT drill a test
port hole in polypropylene piping. Use the following procedure:
1.
Drill a 11/32” hole in the side wall of the PVC vent pipe. If the hole is
in a horizontal section of the vent pipe, ensure that it is located
away from the bottom where condensation may be flowing back
toward the furnace.
2.
Operate the furnace a minimum of (10 minutes) to ensure stable
operation of the combustion process.
3.
Sample the flue gas as necessary to obtain CO readings.
4.
Using a 1/8” pipe tap, cut threads into the sampling hole of the PVC
pipe.
5.
Use high temp RTV as a sealant on the threads of a 1/8” brass
MPT plug and insert it 3 turns into the hole to correctly seal it.
HEAT PUMP
If heat pump is installed with a furnace the HEAT PUMP jumper must
be set to YES.
DANGER
The temperature rise, or temperature difference between the return
air and the supply (heated) air from the furnace, must be within the
range shown on the furnace rating plate and within the application
limitations shown in SECTION V.
The supply air temperature cannot exceed the
“Maximum Supply
Air Temperature”
specified in these instructions and on the furnace
rating plate. Under NO circumstances can the furnace be allowed to
operate above the Maximum Supply Air Temperature. Operating the
furnace above the Maximum Supply Air Temperature will cause pre-
mature heat exchanger failure, high levels of Carbon Monoxide, a fire
hazard, personal injury, property damage, and/or death.
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