Model DP Oil-Fired Heater
Page 25
6.
Lift up the ignition transformer and put tape over
the front of the cad cell (the burner will not start
unless the cad cell senses no light). Disconnect
the black lead going to the motor. Press the
primary control reset button. Use an insulated
screwdriver to touch the metal blade to one
spring contact on the transformer, and about 3/8"
away from the other spring contact. If there is
good spark between the blade and the spring, go
to the next step. If there is no spark, replace the
transformer.
7.
Remove the electrode-nozzle assembly and
inspect the high voltage sections for fouling,
cracked insulators or burnt electrodes. Replace
any defective parts.
8.
If the flame is poor quality or intermittent, use a
pressure gauge to check the nozzle pressure. If
the pressure is below 100 psi, but steady, reset it
to 100 psi and go to step 9. If the pressure is not
steady, use the attached Sundstrand Field Service
bulletin to check out the fuel unit. An unsteady
pressure reading could be a sign of a dirty oil
filter.
9.
Replace the burner nozzle with the nozzle called
out on the heater rating plate and go to step 10.
Replace nozzles once a year as part of the
annual cleaning and inspection service.
10. Check the C0
2
Of the flue gases. The reading
should be between 11.5 to 12.5%. If the reading
is different, go to Section 9.2.3.4.
9.2.3.3
Oil Burner Will Not Shut Off
Remove one of the thermostat leads from the
primary control. If the oil burner shuts off, the problem
is in the heater control circuit. The circuit includes the
pressure switch, high limit safety switch, thermostat
and wire harness. Check for worn insulation on the
wire harness, which could cause a short. Check
operation of the thermostat and pressure switch.
9.2.3.4
Setting the Correct Fuel-Air
Mixture
Measure the C0
2
. If it measures less than 11.5%,
decrease the air supply. If it measures higher than
12.5%, increase the air supply.
When the fuel-air setting is correct, there will be
zero smoke. If there are still traces of smoke after
adjusting the fuel-air mixture, slowly increase the air
supply until the smoke disappears.
Use the proper instruments to measure both the
smoke and C0
2
.
1.
Too Much Air
(low C0
2
)
Too much air decreases the efficiency of the
heater, and causes overheating of the jacket by
pressurizing the firebox. Too much air can also
cause poor ignition and a pulsating flame. If the
C0
2
reading is below 11.5%, reduce the air
adjustment openings on the burner.
2.
Not Enough Air
(high C0
2
)
Not enough air is much easier to detect. The
flame is dark yellow and the heater will smoke.
Generally, the C0
2
reading will be above 12 %
when not enough air is provided.
Lacking proper instruments, a temporary fuel-air
adjustment can be made. Close the end shutter
and then slowly close the air bank until the heater
starts to smoke. Slowly open the end shutter until
the smoke completely disappears. The fuel-air
mixture will be close to the correct setting.
Figure 22. Electrode Adjustment.