Heat pumps · Error codes · Trianco
E09Trianco · Activair R410A indoor wall hung 3kW (S300)
E09 on a Trianco Activair R410A indoor wall hung 3kW: Winter frost protection (ambient temperature is too low)
Short answer
On a Trianco heat pump, E09 means: Winter frost protection (ambient temperature is too low). The manual does not say whether the heat pump stops.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Winter frost protection (ambient temperature is too low).
Part involved: ambient / water temperature protection logic.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
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
- The ambient temperature is too low, please drain the water from the water side heat exchanger.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer.
What you might notice
Sources
- Trianco Activair Wall Hung Air Source Heat Pump S300 (R410A indoor) - Installation Operation and Service Manual ↗ · 2023-07 · page 33 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026