E065 on a Trianco heat pump: Water(Out) High Temp Prot
Short answer
On a Trianco heat pump, E065 means: Water(Out) High Temp Prot. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 4 sources
What it means
On the Activair Commercial R290 50kW (FG9550)
The manual says: Water(Out) High Temp Prot.
Part involved: water flow / water temperature.
Likely causes:
- Excessively high water outlet temperature.
On the Activair High Temperature R290 (5/9/15/22kW)
The manual says: High water outlet temp. protection.
Part involved: water flow / water temperature.
Likely causes:
- Water flow too low / outlet water too high.
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
The manual says: Overhigh Outlet Water Temp.
Part involved: water flow / water temperature.
Likely causes:
- No water/little water in water system.
On the Activair Pro (AI) R290 6/12/17kW
The manual says: Overhigh Outlet Water Temp.
Part involved: water flow / water temperature.
Likely causes:
- No water/little water in water system.
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).
- Check the heating system pressure gauge reading (if one is fitted) and tell your engineer if it is below the level set at commissioning; do not attempt to refill unless you have been shown how.
What the engineer will check
On the Activair Commercial R290 50kW (FG9550)
- Adjust the outlet water temperature < A07-10C.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
On the Activair High Temperature R290 (5/9/15/22kW)
- Check if the water flow is too low and whether the outlet water is too high.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
- Check the pipe water flow and water pump.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
On the Activair Pro (AI) R290 6/12/17kW
- Check the pipe water flow and water pump.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
What you might notice
Sources
- Trianco Activair Commercial High Temperature Air Source Heat Pump (R290 50kW FG9550) - Installation Operation and Service Manual ↗ · 2024-10 · page 39 · Reviewed 23 September 2026
- Trianco Activair High Temperature Air Source Heat Pump (R290 5/9/15/22kW) - Installation Operation and Service Manual ↗ · November 2024 (PDF regenerated 2026-08) · page 35 · Reviewed 23 September 2026
- Trianco Activair R290 High Temperature Indoor Air Source Heat Pump (3.2kW wall hung) - Installation Operation and Service Manual ↗ · 2026-08 · page 33 · Reviewed 23 September 2026
- Trianco Activair Pro Air Source Heat Pump (R290 6/12/17kW) - Installation Operation and Service Manual ↗ · 06/2026 · page 40 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026