Schreiber Chillers 15MEDAC email - Manual (Page 26)

to allow for flow disruptions caused by a changed in valve position or bubbles in the
system.
Backflow Kit
Since the chilled water reservoir is vented to the atmosphere, water in pipes above the
water level of the reservoir will flow back and overflow the reservoir when the pumps
are shut off. To prevent this, a backflow kit consisting of a solenoid valve on the return
line on chilled water return, and a check valve on the pump discharge is provided. The
solenoid valve is a normally closed valve that is energizes whenever the pump contactor
is energized.
The backflow kit also keeps the entire piping loop full of water during shut down. In
some cases (including startup) the pump will start when the pipe is not full. Since the
flow switch is on the return line, the pump may alarm on a flow error on pumped
startup, because the time required to fill the pipes and trigger the flow switch was
longer than the time delay at pump startup. The alarm can be reset, or the flow time
delay temporarily increased to allow for pipe filling.