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B. Symptom: Burner short cycles on high limit thermostat, but does not “lock out”
on oil primary safety control.
Items to check:
1) Open dampers or registers in the air distribution system. Clear any duct
system restrictions.
2) Inspect and clean all air filters in the air distribution system.
3) Inspect blower for interference with rotation or locked rotor condition.
Also, confirm the blower wheel is secured to the fan motor shaft.
4) The fan motor or run capacitor may be damaged. Test and replace the
motor or capacitor, as required.
5) Increase fan speed.
C. Symptom: Burner short cycles on high limit thermostat, but does not “lock
out” on oil primary safety control.
Items to check:
1) Open dampers or registers in the air distribution system. Clear any duct
system restrictions.
2) Inspect and clean all air filters in the air distribution system.
3) Inspect blower for interference with rotation or locked rotor condition.
Also, confirm the blower wheel is secured to the fan motor shaft.
4) The fan motor or run capacitor may be damaged. Test and replace the
motor or capacitor, as required.
5) Increase fan speed.
6) Measure the draft at the point where the vent connector attaches to the
heat exchanger flue pipe. With the burner operating, the stack draft
should not exceed 0.05 in. W.G. If the stack draft has been adjusted
above this value to give the proper overfire draft, the heat exchanger will
require cleaning. If there is little or no stack draft, the chimney flue way
may require cleaning, the chimney is too restrictive, or a downdraft
condition exists.
D. Symptom: Furnace blower will not start.
Items to check:
1) Confirm there is 120 VAC at the blower terminal labeled “HEAT” on the
oil furnace control.
2) If there is not 120 VAC at the blower motor terminal, measure the
voltage at the S1 terminal on the oil furnace control. If the fan can be
activated by itself from the room thermostat subbase, confirm it will
operate. If so, the oil furnace control may have a burnt or damaged
relay. Confirm and replace the control if necessary.
3) If there is 120 VAC at the blower motor terminal “HEAT”, either the run capacitor or
blower motor may be damaged. Test and replace the capacitor or motor, as required.
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