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The mcx152b has the EXV driver included, and it is controlled by stepper motor driver
• External Coil Control: this section controls the 2 Fan condenser speed to keep the discharge pressure at the SP.
General Principle:
• Control fan speed and number of fans running based on compressor discharge pressure.
• Increase air flow (fan speed, number of fans) when pressure is higher than target.
• Reduce air flow (fan speed, number of fans) when pressure is lower than target.
• Increase target discharge pressure when the EEV is fully open (this may be happening for Data Center applications, and or chiller
starting in a building after being off for a long time and with high water temperature e.g. 80F).
• Eliminate constant fan cycling between 2 fans and 1 fan.
• Minimize fan cycling in low ambient conditions between no fans and one fan running to the extent possible (very frequent fan cycling
could cause MCHE condenser coil thermal fatigue failure).
• Information from Daikin/Clima-flex is that fans could go down to 5% of max speed.
• When running one fan only – run the fans that is nearer to the condenser inlet/outlet piping and turn off the one farther away.
iom-clic-cf-eng
Figure 68. Brick for EXV control
102
Mother /Son Logic
www.clima-flex.com
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