Section 12: Flow Switch
The function of the flow switch is to switch off the chiller unit when a low water flow rate
condition is detected in the piping. Such occurances may happen due to:
1. pump failure
2. blocked BPHE
3. accidental closing of shut-off valves
4. failure of control valves
This protection against low water flow rate is necessary to prevent the water from freezing in the
BPHE. Ice formation in between the plates in the BPHE will cause cracking.
The mini chiller has a flow switch installed in the piping, at the following location:
Water out
Water in
BPHE
Flow switch
The flow switch used in the chiller is JOHNSON CONTROLS model F61KB or F61SB.
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However, for field replacements, other brands of equivalent sizes may be used.
The flow switch is of the paddle type whereby the switch is connected mechanically to a length of
stainless steel paddles which the water flow will impact upon. As a result, the paddle will move in
the flow direction and thus closes the electrical contact.
The length of the paddles can be adjusted by selecting the number of segments to use. The
paddles can also be trimmed with a pair of scissors to suit requirement.
Note ##
Or equivalent; Flow switch
used only in A and B series
chillers. paddle segments
Flow
Section 12 Page 141
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