66324-YIM-B-1004
Unitary Products Group 17
HOT SURFACE PILOT INSTRUCTIONS
To check, adjust or remove the hot surface pilot assembly,
CLOSE THE MAIN MANUAL SHUT-OFF VALVE AND SHUT
OFF ALL POWER TO THE UNIT.
The pilot flame should envelope 1/2 inch of the end of the
flame sensor and not contain any yellow color, see Figure 7.
To adjust the pilot flame:
1. Remove the pilot adjustment cover screw.
2. Adjust the pilot adjustment screw to achieve the proper
pilot flame.
3. Replace the pilot adjustment cover screw after the pilot
flame is set.
To remove the hot surface pilot assembly:
1. Disconnect the wiring from the gas valve to the hot sur-
face pilot assembly.
2. Remove the two (2) #8 screws holding the hot surface
pilot assembly in place.
3. Remove the hot surface pilot assembly.
To remove the hot surface ignitor and flame sensor assem-
bly:
1. Remove the clip attaching the ignitor and sensor assem-
bly as shown in Figure 8.
2. Lift the pilot and sensor from the assembly. Care must be
taken not to damage the pilot or sensor when removing
this assembly.
ADJUSTMENT OF TEMPERATURE RISE
The temperature rise (or temperature difference between the
return air and the heated air from the furnace) must lie within
the range shown on the rating plate and the data in Tables 3
and 4.
After the temperature rise has been determined, the CFM can
be calculated as follows:
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts about six feet from the furnace where
they will not be affected by radiant heat. Increase the blower
CFM to decrease the temperature rise; decrease the blower
CFM to increase the rise.
DIRECT DRIVE BLOWER
All units have direct drive multi-speed blower motors. Refer to
the unit wiring diagram and connect the blower motor for the
desired CFM.
CHECKING GAS INPUT
NATURAL GAS
1. Turn off all other gas appliances connected to the gas
meter.
2. With the furnace turned on, measure the time needed for
one revolution of the hand on the smallest dial on the
meter. A typical gas meter usually has a 1/2 or a 1 cubic
foot test dial.
3. Using the number of seconds for each revolution and the
size of the test dial increment, find the cubic feet of gas
consumed per hour from Table 9.
If the actual input is not within 5% of the furnace rating with
allowance being made for the permissible range of the regu-
lator setting, replace the orifice spuds with spuds of the
proper size.
FIGURE 12 - PROPER FLAME ADJUSTMENT
FIGURE 13 - IGNITOR AND FLAME SENSOR
ASSEMBLY
3 /8
Degrees F Temp Rise
BTUHOutput
1.08 CFM×
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=
OR
CFM
BTUH Output
1.08 Degrees F Temp Rise×
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