TMP
Oil Furnaces
–
Furnace Manual
670-000-004/1010
19
9
Troubleshooting
Check 120 volt supply to furnace. If there is no supply
To successfully service the oil furnace, you must
voltage, check fuses and service switch. CAUTION :
have these instruments :
When testing electrical equipment, always follow
smoke tester
standard electrical safety procedures.
carbon-dioxide (CO
2
) or oxygen (O
2
) analyzer
draft gauge (scale should read from -.01” w.c. to -.25” w.c.)
volt/OHM/milliamper multimeter
pressure gauge capable of reading 0-150 lb/sq. inch (for oil only)
Be familiar with these instruments as well as the burner
manufacturers recommended settings.
Before beginning these troubleshooting procedures, ALWAYS :
Make sure thermostat is calling for burner operation.
Check oil supply and make sure all valves are open.
Symptom – Burner
Check fuses and make sure service switch
is on.
Check for voltage from primary relay to
burner motor. Make sure the primary relay
has not locked out on safety.
Check for line voltage into furnace junction
box.
Make sure the thermostat is calling for heat and
that the wiring to the thermostat is correct and tight.
If the primary relay control is not popping
out
the
reset
button,
measure
the
milliamperage at the thermostat and set the
heat-anticipator accordingly. A lso check
wiring from the thermostat to the burner.
Check the alignment of the cad cell to
assure it is aimed at the fire.
Check nozzle and electr ode position.
Check ignition transformer output
(Reference burner manufacturers
instructions).
Check tube insertion and alignment.
Check nozzle and electrode position
(Reference burner manufacturers
instructions).
Replace nozzle.
Check
pump
pressure
(varies
with
manufacturer and application; see burne r
manual).
Check overfire draft.
1. Remove CAD cell leadwires from the f-f
terminals on the primary safety control, then
start burner. Shortly after burner starts,
place
a
temporary
jumper
between
terminals f-f. Connect ohmeter across CAD
cell leadwires-resistance should be under
1,600 ohms.
3. With burner off, check dark cell resistance
across CAD cell leadwires. Resistance
should be greater than 20,000 ohms. If cell
resistances
are
different
from
above,
recheck wiring and location of cell, etc. If
necessary, replace plug-in portion of cell.
2. Stop burner and remove tempor ary jumper.
Possible correct ions :
To check CAD cell operation, use the
following procedure :
Burner motor does not start.
Unable to achieve clean combustion
by setting air adjustments.
Burner short cycles or locks out on
primary relay safety.
Symptom – Furnace blower
Check for 120V to the blower motor. If
present, replace motor.
Check wiring from Fan and Limit control. See
if blower motor will run when it is switched on
manually at the thermostat sub-base (if sub-
base is installed).
Blower short cycles on limit control.
Return ducts may be undersized.
Possible corrections :
Adjust fan "off" setting at 90
o
and adjust fan
"on" setting setting at 130
o
.
Furnace blower will not start.
Blower cycles on and off after the
burner has shut down.
