B9 - testing the flow switch, Testing the flow switch – LAARS NeoTherm NTV (Sizes 150–285 MBTU/h) - Service Manual User Manual
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Service Manual NeoTherm 80 - NeoTherm 285
Testing the Flow Switch
The flow switch uses a set of paddles to sense water
flowing through the system. See Fig. B9-1. When
water is flowing, the switch is normally closed (N.C.).
If the water flow stops, the switch opens. After a “no
flow” condition, the switch resets itself immediately
and automatically.
Use a volt-ohmmeter to test the continuity through
the switch. With the paddles in the “relaxed” position
(standing upright), the switch should be open. Bend
the paddles slightly to one side, and you should see
the switch close.
Note - There is a seal at the base of the paddle as-
sembly. If this seal fails, it can allow water to leak
into the connection box. From there, the water can
flow through conduits to other parts of the control
system in the NeoTherm unit.
If it is necessary to replace the flow switch, see Sec-
Fig. B9-1 – Typical flow switch
B9