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MECHANICAL PROBLEM
When heater is turned on nothing
happens.
Thermostat in "ON" position causes
relay and pump to operate, but
heater does not fire.
Continuous shut down of manual
reset High Limit.
Sooting
CAUTION-Soot may be combus-
tible. Wet down and exercise
caution when cleaning.
Continuous shut down of low water
cut-off or flow switch.
Low flame.
Outer jacket very hot
(blistered paint)
Combustion fan not running.
(If applicable)
POSSIBLE CAUSE
No power to the heater………………….
Bad transformer………………………….
Inoperative thermostat…………………..
Inoperative toggle switch………………..
Inoperative relay………………………….
Main gas valve closed………………......
Plugged bleed line on gas valve or
gas pressure regulator…………………..
Broken pump coupler……………………
Shutdown by low water cut-off,
caused by air……………………………..
Gas valve defective……………………..
Temperature setting too low…………….
Low water flow……………………………
Interrupted pump operation……………..
Modulating control set too high………..
Mechanical modulating control…………
Air starvation……………………………..
Condensation…………………………….
Toxic fumes which cause a chemical
reaction with copper tubes or destroy
combustion……………………………….
Improper venting…………………………
Insufficient system flow………………….
Low water due to leaking………………..
Air in system……………………………...
Line strainer dirty…………………………
Lime in Heat Exchanger…………………
Low gas supply…………………………..
Insects or debris clogging……………….
Burner intake ports low gas pressure….
Venting or combustion air……………….
Broken refractory…..…………………….
Fan relay................................................
Fan.........................................................
CORRECTIVE ACTION
Check the circuit breaker, outdoor con-
troller, etc., upstream of heater.
If power to Leads L1 and L2 of trans-
former, but no power on 24V side, re-
place.
Jumper thermostat, replace with new if
heater fires.
If power to toggle switch, but not through
switch, replace.
If power to relay, but not operating, re-
place.
Open valve.
Loosen bleed line and clean.
Replace coupler. Inspect bearing as-
sembly, and if frozen, lubricate or re-
place.
Bleed air from system.
Check for power to gas valve. If valve has
power but will not open, check vent tube
for blockage. If clear, replace valve.
Reset High Limit to higher temperature.
Check system water pumps.
Check pump oil if necessary.
Reset modulator to a lower setting.
Check and replace if necessary.
Refer to installation instructions regard-
ing combustion air requirements.
Set bypass valve to prevent heater inlet
temperature from dropping below 105° F.
Remove all sources of fumes, such as
freon or chloride, or isolate the heater.
Follow recommended vent installation
instructions.
Check pumps and piping.
Inspect for leaking and repair.
Inspect for leakage and repair. Install an
automatic air vent.
Clean.
Ream tubes.
Debris in gas line (pipe dope, rocks, etc.).
Gas line too small.
Improper size gas meter.
Gas regulator adjustment.
Clean burners.
Adjust gas pressure.
Refer to installation instructions regard-
ing combustion air requirement.
Replace refractory panels.
Replace fan relay.
Loose wire connection.
Failed fan motor.
TROUBLESHOOTING
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