American Water Heater GAS-FIRED COMMERCIAL WATER HEATER - Manual (Page 36)

36
Test or Condition: Result: Action Taken:
Are burners operating? If pilot does not light and pilot is
not sparking, check to make sure
flue damper is in the full open
position. Damper opens?
YES
↓ NO→
Check flue damper wiring.
Check for 24 volts at yellow wire
from thermostat to damper. If
damper still does not open check
for 24 volts between red and
white wires to damper. If damper
does not open when voltage is
present and thermostat is closed,
replace damper operator.
If damper opens, but pilot does
light or spark: Check black wire from damper
for 24 volts to ground. If no
voltage is present, but damper is
open and voltage is present
between yellow wire and ground,
end switch in damper may be
faulty. Replace damper operator.
Does pilot spark without lighting
pilot? Make sure there is
sufficient gas pressure at the gas
valve inlet. Check the nameplate
for minimum gas supply
pressures for the type of gas
used. Check for plugged pilot
orifice. If the pilot valve will not open
when voltage is present to the to
the PV terminal and the common
terminal “PV/MV” wire has
continuity to the module, the gas
valve may be defective. If no
voltage is present at “PV” on the
ignition control and the ECO is
closed (power to 24V and 24V
GND terminals of module) the
ignition control module may be
defective. Replace and recheck
system.
Check gas valve by measuring
voltage from “PV” to ground. If
no voltage, check continuity
across ECO circuit of thermostat
(red wires). If ECO is open, it
should reset after tank cools
below 160°F (71°C). If it does
not reset, replace sensing bulb
with the ECO. If ECO has
opened, there may be a problem
with the thermostat. Make sure pilot flame is steady
and envelopes the electrode or
flame sensor. Turn pilot
adjustment screw counter-
clockwise to increase size of pilot
flame. Make sure pilot shield is
in place.
Pilot lights, but main gas does
not come on. If pilot flame is stable, check for
voltage at the “MV” terminal at
the ignition module and gas
valve. If no voltage is present at
the ignition module, replace
control. If voltage is present at
the gas valve, replace valve.
Troubleshooting Procedure for Electronic Thermostat (continued)-
If water temperature is too cold or heater does not come on, proceed as
follows (continued from table above):
Test or Condition:
Result: Action Taken:
If power is not present at the
“NO” terminal of the Disconnect sensor leads from
electronic control module and Sensor(s) may be shorted or
open. Check continuity of
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