Heat pumps · Error codes · Cool Energy
E042Cool Energy · EcoSyn wall-hung exhaust-air DHW heat pump
E042 on a Cool Energy EcoSyn wall-hung exhaust-air DHW heat pump: Anti-legionella function error
Short answer
On a Cool Energy heat pump, E042 means: Anti-legionella function error. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Anti-legionella function error.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
What you can check
- Read and note the code shown on the controller display, then contact your installer or service engineer.
- Check the heat pump's breaker/isolator at the consumer unit is switched on (do not repeatedly reset if it trips).
- The manual allows the user to press control field no. 4 to restart.
What the engineer will check
- Power-cycle / re-initialise parameters as instructed by the manufacturer.
- Check controller firmware/parameters.
- Replace controller/PCB if the fault persists.
Who to ask for: heat pump controls.
Certification: Electrical competence.
What you might notice
Sources
- EcoSyn 80/100 Installation, Operation & Maintenance Manual Rev1.2 ↗ · Rev1.2 · page 23 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026