Ac High-Limit Thermostat - Aqua-Hot 200 Series Service Manual

High-Limit Thermostats

AC High-Limit Thermostat

Introduction:
The AC high-limit thermostat serves as a safety measure
in the event that the electric heating element continues
to operate after the maximum operating temperature has
been reached. The high-limit thermostat allows the current
for the heating element to pass through until the boiler tank
reaches a temperature of 215°F. Should this temperature
be reached, the high-limit thermostat blocks the current to
the element, preventing the element to continue to operate.
NOTE: If the high-limit thermostat is tripped, it is
recommended to test the control thermostat and AC relay
for proper operation.
Begin troubleshooting the AC High-Limit Thermostat if the
electric element fails to operate correctly.
Troubleshooting Guidelines:
The following conditions must be met before the AC High-
Limit Thermostat can be diagnosed, and if necessary, repaired.
• The fl uid expansion bottle is fi lled to at least the "COLD"
mark.
• Verify that all in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the Aqua-
Hot's electric element.
If any of the above conditions are not met, correct them before
continuing with troubleshooting. Results of the troubleshooting
procedure cannot be verifi ed if the conditions listed above are
not fulfi lled.
Failure to disconnect all power supplies and/or allow
the unit to cool before servicing could cause serious
damage or personal injury.
Troubleshooting Procedure:
1. Verify the following before troubleshooting the AC high-limit
thermostat:
• The control thermostat is calling for heat.
• The interlock switch is depressed.
• The overfl ow bottle is adequately fi lled.
• The high-limit thermostats are not tripped.
p. 18 ©Aqua-Hot® 250 Series Diesel Service Manual
• The fuses in the relay control board are functional.
2. Ensure that the unit has been shut down and completely
cooled before continuing.
3. Shut off the coach-side power breaker to the Aqua-Hot.
4. Disconnect the 3-pin AC Molex plug from the AC relay
enclosure. Leave the DC power supply connected.
5. Activate the "ELECTRIC" switch on the switch panel inside
the coach.
6. Using a multimeter, test for continuity across the AC high-
limit thermostat by placing one lead on the unit-side Molex
connection as shown below.
7. If no continuity exists, locate the AC high-limit thermostat
and depress the center button to reset it. Retest for
continuity.
8. Move the electric switch to the OFF position. Reset for
continuity. If continuity still exists, replace the AC relay.
AC High Limit
Thermostat
Figure 18
Figure 19
Figure 20