16
V E N T - F R E E G A S H E A T E R S E R V I C E M A N U A L
COLD-START CHOKE ADJUSTMENT
GRH/OV 027
Pilot ignites but will not stay lit
Possible Causes
1.
Control knob not held down long enough
2.
Defective valve or thermocouple
3.
Not enough fresh air
4.
Wrong air/gas mixture at pilot
Procedures
1. Be sure that the control knob is held down
long enough to get the thermocouple hot.
After lighting the pilot, hold the control
knob down for 10 to 15 seconds before
releasing.
2. Check to be sure that the pilot flame pat-
tern is correct (see Figures 15 & 16).
Figure 15. Correct LP Pilot Flame
Figure 16. Correct Natural Gas Pilot Flame
If the pilot flame appears to be normal,
check the control valve according to the
test procedure outlined on page 12 under
“Testing Control Valve and Thermocouple”.
If the valve passes the testing, the thermo-
couple may be defective and should be
replaced.
3. If the pilot flame is lifting off the thermo-
couple as shown in Figure 17, check to be
sure that the room is properly ventilated.
See
“SPECIFICATIONS”, page 13, for the
minimum fresh air openings required. If
necessary, instruct the user to slightly open
a window for proper ventilation.
4. Be sure that strong or gusty drafts are not
blowing on the heater. If necessary, the
GRH/OV 007
GOOD PILOT/LP
GRH/OV 009
GOOD PILOT
GRH/OV 008
BAD PILOT/LP
LP
GRH/OV 010
BAD PILOT
Natural Gas
Figure 18. Pilot Barrel Liftoff
LP
Figure 17. Pilot Barrel Liftoff
heater should be relocated to a more
protected area.
If the pilot flame is incorrect as shown in
Figure 18, it is possible that the cold-start
choke is allowing too much air to enter the
pilot tube. Turn the heater off, remove the
front cover from the heater, and inspect the
cold-start choke on the pilot tube.
Insert a 1/4 inch diameter rod (i.e., a 1/4
inch drill bit will do) under the bi-metal strip
to adjust the cold-start choke to the nearly
closed position (see Figure 19). Relight the
pilot and observe to see if the pilot flame is
more stable. Replace the front cover.
GRH/OV 007A
FLAME LIFTING/LP
Liftoff
LP
Figure 19. Cold-Start Choke Adjustment
GRH/OV 009A
FLAME LIFTING
Liftoff
Natural Gas
Figure 18. Thermocouple Liftoff
1/4" Rod
