Heat pumps · Error codes · Trianco
E042Trianco · Activair Pro (AI) R290 6/12/17kW
E042 on a Trianco Activair Pro R290 6/12/17kW: DHW Electric Heater Overheat Fault
Short answer
On a Trianco heat pump, E042 means: DHW Electric Heater Overheat Fault. 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: DHW Electric Heater Overheat Fault.
Part involved: electric heater / immersion overheat protection.
Likely causes:
- Overload protection switch disconnected when the electric heating of the hot water tank was activated.
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
- Note the exact code shown on the controller (a photo helps) and report it to your installer or the manufacturer's service line.
- Check the heat pump's supply breaker/isolator at the consumer unit is on (do not open any casing).
What the engineer will check
- Check the wiring of the electric heating overload switch in the hot water tank for proper connection and inspect the condition of the overload switch.
Who to ask for: electrical.
Certification: Electrical competence (Part P / qualified electrician).
What you might notice
Sources
- Trianco Activair Pro Air Source Heat Pump (R290 6/12/17kW) - Installation Operation and Service Manual ↗ · 06/2026 · page 41 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026