General Assist Technical Reference

VII Outdoor EEV Control

Electronic Expansion Valve operating ranges and control
Technical reference for EEV1 and EEV2 operation
The outdoor unit uses two Electronic Expansion Valves, EEV1 and EEV2. Their commanded opening position varies according to the operating mode and system operating condition.

1. Expansion Valve Control

EEV control is initialised under the following conditions:

  • When power is turned on.
  • When operation is stopped.
EEVOperation ModeControl Range
OperationStop
EEV1Cooling0 pulses0 pulses
Heating55 – 500 pulses
EEV2Cooling55 – 500 pulses0 pulses
Heating
Important: A command of 0 pulses represents the valve being driven to its closed position.

2. Cooling Mode

EEV10 pulses
EEV255 – 500 pulses

During cooling operation, EEV1 is basically controlled at 0 pulses.

3. Heating Mode

EEV155 – 500 pulses
EEV255 – 500 pulses

During heating operation, the EEV is controlled so that the system approaches the target discharge temperature.

The target discharge temperature is calculated from:

  • High pressure
  • Low pressure
Control principle: Rather than maintaining one fixed opening position during heating, the expansion valve is modulated within its permitted 55 – 500 pulse range as the control system works towards the calculated target discharge temperature.

4. Diagnostic Reference

When reviewing EEV operation, compare the commanded valve position with the expected range for the current operating mode.

Operating ConditionEEV1EEV2
Cooling0 pulses55 – 500 pulses
Heating55 – 500 pulses55 – 500 pulses
Unit stopped0 pulses0 pulses
Diagnostic caution: The EEV pulse position is a commanded control position. A pulse value alone should not be used to confirm that the mechanical valve is physically operating correctly.

5. Quick Reference

Expected EEV Control
  • Cooling – EEV1: 0 pulses
  • Cooling – EEV2: 55 – 500 pulses
  • Heating – EEV1: 55 – 500 pulses
  • Heating – EEV2: 55 – 500 pulses
  • Stopped – EEV1: 0 pulses
  • Stopped – EEV2: 0 pulses