5894307-UIM-B-0920
Johnson Controls Ducted Systems
27
ADJUSTMENT OF TEMPERATURE RISE
After about 5 min of operation, determine the furnace temperature rise.
Take readings of both the return air and the heated air in the ducts
about 6 ft (1.83 m) from the furnace, where they are not affected by
radiant heat. Increase the blower speed to decrease the temperature
rise. Decrease the blower speed to increase the rise.
This furnace has a standard ECM motor. The blower motor speed taps
are located on the furnace control board in the blower compartment.
See Figure 32 and refer to the unit wiring label to change the blower
speed. Place all unused motor leads on the PARK terminals. Two PARK
terminals are provided. To use the same speed tap for heating and cool-
ing, the terminals must be jumpered together. This control changes
blower speeds based on other 24-V thermostat inputs (Y, W) respec-
tively.
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 s. The fan off delay has four settings
(A = 60 s, B = 90 s, C = 120 s, and D = 180 s). The fan off delay is fac-
tory set to 120 s. 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 can be adjusted by positioning the jumper on
two of the four pins as shown in Figure 32.
The furnace is also equipped with a cooling fan on time delay. The cool-
ing fan on delay has two settings (A = 6 s, B = 24 s). The cooling fan on
delay can be adjusted by positioning the COOL jumper as shown in Fig-
ure 32.
TAKING A FLUE GAS SAMPLE
If it is necessary to obtain a flue gas sample for analysis, it is permissi-
ble to drill a small hole in the plastic flue pipe for a sample probe, pro-
vided that the vent piping is PVC and the hole is correctly sealed
afterwards. If using a polypropylene vent system, the vent system’s
manufacturer test port fitting must be used.
DO NOT
drill a test port
hole in polypropylene piping. Use the following procedure:
1. Drill an 11/32 in. hole in the side wall of the PVC vent pipe. If the
hole is in a horizontal section of the vent pipe, make sure that it is
located away from the bottom where condensation may be flowing
back toward the furnace.
2. Operate the furnace for a minimum of 10 min to ensure stable oper-
ation of the combustion process.
3. Sample the flue gas as necessary to obtain CO readings.
4. Using a 1/8 in. 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 in. brass
MPT plug and insert it three turns into the hole to correctly seal it.
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 Table 4.
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.
!
Figure 32:
Furnace Control Board
DIAGNOSTIC
ERROR CODE
BUTTON
COOL BLOWER
ON JUMPER
HEAT BLOWER
OFF JUMPER
HUMIDIFIER
TERMINAL
ELECTRONIC AIR CLEANER
TERMINAL
3 AMP
FUSE
DIAGNOSTIC
LED
ID PLUG
A1104-001
