Description
The Hoffman Controls 880-35 Low Ambient Head Pressure Control is designed to modulate energy efficient Electrically Commutated condenser fan Motors (ECM) in air conditioning and refrigeration systems. The 880-35 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 880-35 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 880-35 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.
Hoffman Controls 880-35 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.
Applicable Motors
- ECM (brushless dc) Motors
- Variable Frequency Drive (VFD) Motors
Hoffman Controls 880-35 Features:
- Improves system performance while saving energy
- Non-invasive sensor requires no system penetration
- Eliminates compressor slugging
- Sensing is independent of all refrigerant types
- 20mA motor drive capability modulates up to two typical ECM motors.
- Available 20Vdc, 15mA ECM motor “GO” SIGNAL when required.
- Selectable motor drive output options include adjustable 13-17Vdc peak 80Hz PWM, 0-10Vdc or 10-0Vdc (fail safe) signals.
- Monitor one or two liquid line 10K temperature sensors with the hottest sensor controlling motor operation.
- Adjustable LOW & HIGH sensor set points.
- 24Vdc activated selectable Direct or Reverse acting Heat Pump mode.
- Hard start, self test, set point and motor modulation LED indicator.
- Includes one 10K temperature sensor. Additional sensors available.
Typical Installations:
- Commercial A/C
- Computer rooms
- Hospitals
- Grocery and convenience stores
- Frozen food storage
- Humidity or temperature sensitive environments
- Cooling tower fans, glycol coolers
- Liquid heat exchangers
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