Laars MASCOT LX, Service Manual

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37
Mascot LX Service Manual
Outlet Water Temperature Sensor
The outlet water temperature sensor allows the con-
trol system to monitor the temperature of the water
as it leaves the Mascot LX unit. A typical installation
for the outlet water temperature sensor is shown in
Fig. B4-1.
This sensor assembly includes two electronic de-
vices called “thermistors.” The second sensor acts
as the high water temperature safety limit. As long
as the resistance readings from both sensors agree,
the Mascot LX will continue to operate. If there is
a large difference between the readings, or if one
of the thermistors is “open” or “shorted,” the control
system will shut down the Mascot LX unit.
For instructions on testing the assembly, see Section
B9.
Replacement Procedure -
Tools and equipment required:
• 17 mm wrench or crescent wrench
• Pipe dope or Teflon® tape
Procedure:
1. Turn off power to the unit. Use the main discon-
nect switch mounted on the front panel.
2. Isolate the boiler. Turn off the water shutoff
valves located upstream and downstream of the
unit.
3. Drain the boiler.
4. Remove the upper front cover. The outlet water
temperature sensor is mounted in the upper left
corner of the unit. See Fig. B4-1.
5. Unplug the wiring connector (four wires). The
connector is locked in place by a “squeeze tab.”
Press on the tab to release the connector.
6. Unscrew the sensor using the 17 mm wrench.
Turn counter-clockwise to unscrew the part.
7. To test the part for accuracy, see Section B9.
8. To reassemble, reverse the process we have
just described. Be sure to use pipe dope or
Teflon tape on the threaded part of the sensor.
Fig. B4-1 - Outlet Water Temperature Sensor
Outlet water
temperature
sensors
Water outlet
pipe
B4