Verifying Burner Operation; Verifying Operation Of The Supply Air Limit Switch - Nordyne CMF95 Series Installation Instructions Manual

NOTE: This furnace is designed to operate with a
maximum external pressure rise of 0.3 inches of water
column.It is important that the duct system be designed
to provide the correct flow rates and external pressure
rise. An improperly designed duct system can result
in nuisance shutdowns, and comfort or noise issues.
3. Adjust all registers and duct dampers to the desired
position and run the furnace for 10 to 15 minutes before
taking any temperature readings.The temperature rise
is the difference between the supply and return air
temperatures.

Verifying Burner Operation

CAUTION:
The door over the burners may only be open
for inspection purposes only.The door must be
installed during unattended operation.
1. Set the thermostat above room temperature and observe
the ignition sequence. NOTE: The burner flame should
carry over immediately between all burners without
lifting off, curling, or floating.The flames should be blue,
without yellow tips.
2. After validating the flame, change thermostat setting to
below room temperature.
3. Verify the burner flame is completely extinguished.
MODEL NUMBER
& HEATING INPUT
(BTUH)
CMF95 045
45,000
CMF95 072
72,000
NOTES:
* Factory Set Cooling Speed.
** Factory Set Heating Speed.
1. Temperature rises (° F) in the table are approximate. Actual temperature rises may vary.
2. Temperature rises shaded in gray are for reference only. These conditions are not recommended.
3. Airflow performance is with a filter.
24
EXTERNAL STATIC PRESSURE (INCHES WATER COLUMN)
MOTOR
0.1
SPEED
CFM RISE
HIGH* 1380 29
MED HIGH 1350 29
MED LOW 1100 36
LOW** 1000 40
HIGH* 1485 43
MED HIGH** 1263 50
MED LOW 1130 56
LOW 880 72
Table 5. Maximum Airflow & Temperature Rises (° F)
4. Replace the burner compartment door.
Verifying Operation of the Supply Air Limit
Switch
Note: A properly functioning limit switch should turn off
the gas valve when the return is blocked (time depends
on how well the return air is blocked). The circulating air
and combustion blowers should continue to run when the
limit switch opens.
1. Verify the blower door is securely mounted in place and
that there is power to the furnace.
2. Block the return airflow to the furnace by installing a
close-off plate in place of or upstream of the filter(s).
3. Set the thermostat above room temperature and observe
the Operating Sequence.
4. Remove the close-off immediately after the limit switch
opens.If the furnace continues to operate with no return
air, set the thermostat below room temperature, shut
off power to the furnace, and replace the limit switch.
0.2 0.3
CFM RISE CFM RISE
1335 30 1290 31
1295 31 1240 32
1055 38 1020 39
970 41 935 42
1440 44 1390 46
1235 51 1205 53
1100 58 1175 54
846 75 830 76
0.4 0.5
CFM RISE CFM RISE
1230 32 1175 34
1190 33 1135 35
975 41 920 43
900 44 860 46
1340 47 1290 49
1160 55 1115 57
1045 61 1000 63
805 79 770 82