Multiaqua CFFWA Series, Operating Manual

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Chiller Controls Sequence of Operation
When powered up, the Multiaqua chiller system energizes the control transformer creating 24 vac control voltage.
First the pump bypass timer is energized and temporarily bypasses the flow switch, energizing the pump relay. The
If the liquid solution temperature controller is calling for cooling the control circuit is routed through the short cycle
pump then starts to move liquid solution through the piping system (in a properly filled and air purged system). The
movement of liquid solution from the pump discharge keeps the flow switch closed. After a 10 second delay the pump
contact opens, connecting the flow switch in series with the high and low pressure switches. The pump will now run
continually unless the power supply is interrupted, or the flow switch opens.
timer and the three safety switches (the flow, high and low pressure switches) to the compressor contactor. This will
energize the compressor(s) and condenser fan motors. The liquid solution controller will open at the user programmed
set point, causing the refrigerant short cycle timer to open it's contact for 5 minutes as it delays before resetting to the
closed position. This will de-energize the compressor. Power fluctuations will also initiate a 5 minute time delay. The
5 minute delay allows the refrigerant system a period for pressure equalization, protecting the compressor(s) from
short cycling.
The chiller temperature controller utilizes a thermistor to monitor the liquid solution temperature change. The
temperature is then compared to the set point and differential temperatures programmed into the control by the user.
The set point is the liquid solution temperature which will cause the control switch to open. For example: The control
set point is programmed at 44°F LWT with a 10°F differential, which opens the controller at 44°F LWT and closes at
54°F. The differential temperature is the number of degrees above set point temperature programmed into the
controller. If liquid solution temperature falls to the set point, the controller cycles the compressors off.
Chillers are shipped with the control set point adjusted to 44°F LWT and a 10°F differential. Liquid solution
temperature set point should not be set below 35°F.
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