The Hoffman Controls 880-90 Low Ambient Head Pressure Control is designed to modulate energy efficient Electrically Commutated condenser fan Motors (ECM) in air conditioning and refrigeration systems. The 880-90 control varies the speed of the condenser fan ECM motor(s) to vary the air volume through the condenser consequently regulating head pressure for proper heat rejection in low ambient temperatures. The 880-90 Head Pressure Control monitors the head pressure by sensing the sub-cooled liquid line temperature by placing a 10K sensor on the refrigerant liquid line. As the liquid line temperature drops, the motor speed will be reduced to prevent freezing of the coil. As minimum motor speed is reached, the control will cycle the motor off until the liquid line coil temperature has returned to safe operating levels. At this point, the motor will modulate back to full speed to maintain proper heat rejection. The 880-90 control provides an adjustable LOW SET point of 40°F to 80°F and an adjustable HIGH SET point of 60°F to 140°F for the ability to custom tune the control for any application. The common settings for most applications is a LOW SET point of 50°F and a HIGH SET point of 80°F. In this example, the condenser fan(s) modulation from full speed occurs at 80°F liquid line (ambients above 60ºF), and reaches minimum speed at 50°F liquid line (ambients below 30°F). The ECM condenser fan motor cycles “OFF” at liquid line temperatures below 50°F, and cycles back “ON” to minimum speed at 53°F liquid line temperature. The ECM condenser fan motor will modulate from minimum speed to full speed between 53°F and 80°F.
Hoffman Controls 880-90 Applications:
Typically utilized on continuously variable speed condenser fan motors (ECM or VFD) in air conditioning and refrigeration systems. Use this Model for control of single motor condenser applications when using up to two temperature sensors of liquid lines. Use the 880-90 Model for control of multiple motors, up to three temperature sensors or three pressure sensors or a 0-10 VDC input. The 880-90 also provides serial Modbus capability if the user desires to read or set any operating parameters remotely. Both models provide PWM, 0-10 VDC, and 10-0 VDC outputs for control of the variable speed fan motors.
- ECM (brushless dc) Motors
- Variable Frequency Drive (VFD) Motors
Hoffman Controls 880-90 Features:
- Improves system performance while saving energy
- Non-invasive sensor requires no system penetration
- Eliminates compressor slugging
- Sensing is independent of all refrigerant types
- 90mA motor drive capability modulates up to nine typical ECM motors.
- Selectable motor drive output options include adjustable 13-17Vdc peak 80Hz PWM, 0-10Vdc or 10-0Vdc (fail safe) signals.
- Monitor up to three liquid line 10K sensors or up to three selectable pressure transducers with the hottest sensor or highest pressure transducer controlling motor operation.
- Available 0-10Vdc control signal input.
- Adjustable LOW & HIGH temperature, pressure or Vdc set points.
- Pressure input calibrated to accept 0.5-4.5Vdc, 500psi ratiometric pressure transducer. Pressure transducers are market available.
- 24Vdc activated selectable Direct or Reverse acting Heat Pump mode.
- Hard start, self test, set point and motor modulation LED indicator.
- Temperature sensors and pressure transducers not included. 10K temperature sensors are available from Hoffman Controls.
- Commercial A/C
- Computer rooms
- Grocery and convenience stores
- Frozen food storage
- Humidity or temperature sensitive environments
- Cooling tower fans, glycol coolers
- Liquid heat exchangers
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