Dc High-Limit Thermostat (Left) - Aqua-Hot 400 Series Service Manual

DC High-Limit Thermostat (Left):

The DC high-limit thermostats serve as a safety measure in
the event that the burner continues to operate after the
maximum operating temperature is reached. The high-limit
thermostats allow the current for the burner to pass through
them until the boiler tank reaches a temperature of 215°F.
Should this temperature be reached, the high-limit thermo-
stat blocks the current to the burner's blower fan, which
prevents the burner from operating.
Troubleshoot the Left Burner DC high-limit thermostat if the
following condition has occurred:
 The burner does not attempt to start.
Troubleshooting:
1. Locate the Left High Limit Thermostat, Wires 32 & 35.
Disconnect the wires from the thermostat and place a
jumper wire between the two wires to bypass the high
limit thermostat. Check the Aqua-Hot for normal opera-
tion.
NOTE: By passing the high-limit thermostats is for testing
only and must not be used for the Aqua-Hot's normal func-
tionality.
2. Disconnect the DC high-limit thermostats' wires, then,
using an ohmmeter, check the 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.
Figure 15
215°F
High Limit
Thermostat
© Aqua-Hot® AHE-400-P01 Service Manual Rev.B June 2014
Aqua-Hot Components
If a thermostat, with the wires removed, that has been reset
does not have continuity, follow the instructions in this sec-
tion to replace the high-limit thermostat.
If an individual wire does not have continuity, that wire must
be replaced.
NOTE: If the high-limit thermostats continue to trip, trouble-
shoot the control thermostat and verify the boiler tank is
full of antifreeze and water heating solution.
Replacement Procedure:
F
AILURE TO DISCONNECT ALL POWER SUPPLIES AND
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 ther-
mostat 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
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