Service manual

— Page 27 —
© January 2013 Aqua-Hot
®
600-D01 Series Hydronic Heating System Service Manual - Rev. A
SECTION 4: AQUA-HOT COMPONENTS
DC High-Limit Thermostat:
The DC high-limit thermostat serves as a safety measure in
the event that the diesel-burner continues to operate after the
maximum operating temperature is reached. The high-limit
thermostat allows the current for the diesel-burner to pass
through it until the boiler tank reaches a temperature of
220°F. Should this temperature be reached, the high-limit
thermostat blocks the current to the diesel-burner’s fuel sole-
noid valve, which prevents the diesel-burner from operating.
Troubleshoot the DC high-limit thermostat if the following
condition has occurred:

The fuel solenoid on the diesel-burner fails to operate.
Troubleshooting:
1
. Remove the Thermostat Access Panel
2.
Place a jumper wire between the blue and purple wires
on the diesel-burner’s Thermostat plug to bypass
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’s normal
functioning.
3.
Disconnect the DC high-limit thermostats’ wires, from
the Webasto Thermostat Plug, then, using a digital volt-
age meter, check the High Limit thermostat for continui-
ty.
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.
B.
Disconnect the wires from the thermostat and re-
check the thermostat for continuity, as well as each
of the thermostat individual wires.
If an individual wire does not have continuity, that
wire must be replaced.
If a thermostat with the wires removed that has been
reset does not have continuity, follow the instruc-
tions in this section to replace the high-limit ther-
mostat.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
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
disconnected.
2.
Remove the Thermostat Access Panel
3.
Remove the two wires on the defective high-limit ther-
mostat from the Webasto Thermostat Plug by pulling
firmly on the wires.
4.
Using a 5/8 wrench or socket, remove the defective high
-limit thermostat from the Aqua-Hot’s boiler tank.
5.
Install the replacement high-limit thermostat into the
port on the Aqua-Hot’s boiler tank and finger-tighten
only (15 in/lbs).
6.
Connect the wires to the Webasto Thermostat plug.
7. Secure the Thermostat Access Panel in place.
8. Test for proper operation.
NOTE: If the high-limit thermostat has tripped, trouble-
shoot the control thermostat, and verify the boiler tank is full
of the antifreeze-water solution.
NOTE: The New thermostat may or may not come with the
two prong plug, to connect to the Webasto Thermostat Plug.
It may be necessary to remove the two prong plug from the
defective thermostat and install it onto the replacement ther-
mostat.