Diesel Burner High Limit Thermostat (Left) - Aqua-Hot 375-d Service Manual

DC High-Limit Thermostat: Left
The left DC high-limit thermostat serve as a safety measure
in the event that the diesel-burner continues to operate after
the maximum operating temperature is reached. The high-
limit thermostats allow the current for the diesel-burner to
pass through them until the boiler tank reaches a temperature
of 215°F. Should this temperature be reached, the left high-
limit thermostat blocks the current to the diesel-burner's
controller, which prevents the diesel-burner from operating.
Troubleshoot the Left DC high-limit thermostat if the follow-
ing condition has occurred:

The diesel-burner fails to operate.

The diesel-burner switch light flashes a 6 fault code.
Troubleshooting:
1. Place a jumper wire between the black (#15) and black
(#16) wires on the diesel-burner's wire harness to by-
pass the high-limit thermostats. Check the Aqua-Hot for
normal operation.
NOTE: Bypassing the high-limit thermostats is for testing
only and must not be used for the Aqua-Hot normal
operation.
2. Disconnect the Left DC high-limit thermostats' wires,
then, using an ohmmeter, check the thermostat for conti-
nuity.
If there is no continuity, complete the following:
A. Press the white reset button on the high-limit ther-
mostat, then re-check for continuity.
®
© 2009 Aqua-Hot 375D Hydronic Heating System Service Manual—Rev. A
S 4: A
ECTION
NOTE: If a thermostat with the wires removed, that
has been reset does not have continuity, follow the
instructions in this section to replace the high-limit
thermostat.
B. Disconnect the wires from the thermostat and re-
check the thermostat for continuity, as well as the
thermostats' individual wires.
If an individual wire does not have continuity, that
wire must be replaced.
Replacement Procedure:
F
AILURE TO DISCONNECT ALL POWER SUPPLIES AND
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY
1. Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been disconnect-
ed.
2. Remove the two wires from the defective high-limit
thermostat by pulling firmly on the wires.
3. Using a 5/8 wrench or socket, remove the defective high
-limit thermostat from the Aqua-Hot's boiler tank.
4. Install the replacement high-limit thermostat into the
port on the Aqua-Hot's boiler tank and finger-tighten
only (15 in/lbs).
5. Connect the wires removed from the defective high-limit
thermostat to the replacement high-limit thermostat.
6. Test for proper operation.
Figure 14
-H C
QUA OT OMPONENTS
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