LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 29)

19
Service Manual - NeoTherm 500
Checking the Low Water Cutoff Switch (continued)
Controller for Low Water Cutoff
The low water cutoff switch operates by passing
a slight electrical current between from a probe to
ground when water is surrounding the probe. If there
is no water, there is no current, and the controller
knows that the water level has dropped.
The low water cutoff controller is shown in Fig. B5-1
The controller has two LED indicators:
• Power (red) – When lighted, the control box has
power.
• Tripped (yellow) – When lighted, the controller
has detected a low water condition.
The controller also has two switches:
• Reset – Use this to cancel the “trip” condition.
• Test – This simulates a “low water” condition.
See “Removing and Replacing the Low Water Cutoff
Switch,” Section B6.
Fig. B5-1 - Controller for low water cutoff
Check for dirty probe.
Probe dirty?
Yes
Wipe down the probe.
(Do this once a year.)
System recently
installed?
Yes Drain and flush the system.
No
The system may have tripped
because of small air bubbles.
B4
cont.
B5