Heat pumps · Error codes · Trianco
E05Trianco · Activair High Temperature R290 (5/9/15/22kW)
E05 on a Trianco Activair High Temperature R290: Water Circuit Frost Protection
Short answer
On a Trianco heat pump, E05 means: Water Circuit Frost Protection. 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: Water Circuit Frost Protection.
Part involved: ambient / water temperature protection logic.
Likely causes:
- Insufficient water flow.
- The outlet water temperature is too low.
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 outdoor unit is not blocked by snow, ice build-up or debris.
- Leave the heat pump powered: frost protection needs a permanent electricity supply.
What the engineer will check
- Check water flow and outlet water temperature.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer.
What you might notice
Sources
- 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 34 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026