Heat pumps · Error codes · Trianco
05Trianco · Activair (first generation) S300/S500/S800/S1200/S1300/S1800
05 on a Trianco Activair S300/S500/S800/S1200/S1300/S1800: Ambient temperature cycle
Short answer
On a Trianco heat pump, 05 means: Ambient temperature cycle. The heat pump stops until the fault clears or is reset.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Ambient temperature cycle.
Part involved: ambient / water temperature protection logic.
Likely causes:
- Ambient (room) temperature too high.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Unit resets automatically when the temperature returns to normal (manual p.21).
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
- When ambient temperature has returned to normal levels, unit will automatically reset.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer.
What you might notice
Sources
- Trianco Activair Air-to-Water Air Source Heat Pump S300 & S500 - User, Installation, Commissioning & Servicing Instructions (224511) ↗ · 224511 · page 21 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026