LAARS NeoTherm NTV (Sizes 150–285 MBTU/h) - Service Manual - Manual (Page 54)

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Service Manual NeoTherm 80 - NeoTherm 285
Fig. B26-1 - Outlet water temperature sensor (typical)
The outlet water temperature switch allows the control
system to monitor the temperature of the water as it
leaves the NT unit. A typical installation for the outlet
water temperature sensor is shown in Fig. B26-1. The
sensor is connected to J8 8-9-10 on the control module.
This sensor assembly includes two electronic devices
called “thermistors.” As long as the resistance readings
from both sensors agree, the NeoTherm will continue to
operate. If there is a large difference between the read-
ings, or if one of the thermistors is “open” or “shorted,”
the control system will shut down the NT unit and display
a “Hold 92” error message.
For instructions on testing the assembly, see Section
B28.
To reset the control system after the outlet sensor trips:
• On a unit with the original (white) user interface -
Press the Reset button near the lower left-hand
corner of the display. This will reset the lockout, and
the lockout code will disappear.
• On a unit with current user interface -
Reset by pressing the OK button.
Removing and Replacing the Outlet Water Temperature Sensor
See Fig. B26-1 for a typical installation.
Tools and equipment required:
• Crescent wrench or 14 mm socket
• Pipe dope or Teflon® tape
Procedure:
1. Turn off power to the system. Use the main disconnect switch mounted above
the front panel.
2. Isolate the boiler. Turn off the water shutoff valves located upstream and down-
stream of the unit.
3. Drain the boiler. The drain valve is located near the lower end of the heat ex-
changer.
Sensor
Water outlet
pipe
Outlet Water Temperature Sensor
B26
B27