AL14 on a MasterTherm heat pump: EVD Evo - alarm of the Electronic Expansion Valve driver
Short answer
On a MasterTherm heat pump, AL14 means: EVD Evo - alarm of the Electronic Expansion Valve driver. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 1 source
What it means
On the pCO5/pGD controller alarms - air/water units (BoxAir, BoxAir Inverter, BoxAir Inverter P, AirMaster, EasyMaster)
The manual says: EVD Evo - alarm of the Electronic Expansion Valve driver.
Part involved: EVD Evo EEV driver module.
When it shows: Control action: Switches off compressor and fan. Operator guidance: Turn power off and on; if persists contact installer / call service.
Likely causes:
- Malfunction of EVD Evo (EVD400) module.
On the pCO5/pGD controller alarms - brine/water and water/water units (AquaMaster, AquaMaster Inverter, Inverter P, Combi)
The manual says: EVD Evo Alarm.
Part involved: EVD Evo EEV driver.
When it shows: Control action: Switches off compressor and brine circulator. Operator guidance: Restart unit power supply; if problem returns call service.
Likely causes:
- Malfunction of EVD Evo module.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Resets automatically after the minimum compressor off time (~6 min) if the same alarm occurs fewer than 3 times per compressor operating hour.
Manual reset: After 3 occurrences in 1 compressor operating hour the unit is blocked (ALARM key lit steadily); manual reset by pressing ALARM key on the alarm display (pGD) or RESET on pGDx Alarm Management.
What you can check
On the pCO5/pGD controller alarms - air/water units (BoxAir, BoxAir Inverter, BoxAir Inverter P, AirMaster, EasyMaster)
- Read and note the alarm (ALx code/text) and the alarm counter shown on the pGD/pGDx display.
- Check the heat pump breaker/isolator in the consumer unit is on.
- Power-cycle the heat pump once at its breaker/isolator as the manual allows.
On the pCO5/pGD controller alarms - brine/water and water/water units (AquaMaster, AquaMaster Inverter, Inverter P, Combi)
- Read and note the alarm (ALx code/text) and the alarm counter shown on the pGD/pGDx display.
- Check the heat pump breaker/isolator in the consumer unit is on.
- Power-cycle the heat pump once at its breaker/isolator.
What the engineer will check
On the pCO5/pGD controller alarms - air/water units (BoxAir, BoxAir Inverter, BoxAir Inverter P, AirMaster, EasyMaster)
- Read detailed EVD alarm (PRG key).
- Check EEV driver, valve and probes.
Who to ask for: heat pump service engineer (refrigeration/controls).
Certification: F-gas certification (refrigerant circuit work); electrical competence for switchboard work.
On the pCO5/pGD controller alarms - brine/water and water/water units (AquaMaster, AquaMaster Inverter, Inverter P, Combi)
- Read detailed EVD alarm.
- Check EEV driver/valve.
Who to ask for: ground source heat pump engineer (refrigeration/controls).
Certification: F-gas certification (refrigerant circuit work); electrical competence for switchboard work.
What you might notice
Sources
- MasterTherm pCO5/pGD digital controller - OEM instruction manual, heat pumps AirMaster, AquaMaster, EasyMaster, BoxAir (Documentation PGD1-MANUAL, Edition 41, sw_11) ↗ · Edition 41 / sw_11 · pages 31, 42-43, 31, 40-41 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026