F06 on a Trianco heat pump: DC Bus Under voltage
Short answer
On a Trianco heat pump, F06 means: DC Bus Under voltage. 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 · 3 sources
What it means
On the Activair High Temperature R290 (5/9/15/22kW)
The manual says: DC Bus Under voltage.
Part involved: compressor driver / inverter board.
Likely causes:
- DC bus voltage below threshold.
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
The manual says: DC Power Bus Undervoltage.
Part involved: compressor driver / inverter board.
Likely causes:
- DC bus voltage < DC bus underload-voltage protection value.
On the Activair Pro (AI) R290 6/12/17kW
The manual says: DC Power Bus Undervoltage Fault.
Part involved: compressor driver / inverter board.
Likely causes:
- DC bus voltage is below the undervoltage protection threshold.
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
On the Activair High Temperature R290 (5/9/15/22kW)
- Check the voltage between DCP-IN and DCN-IN.
- if lower than 300V this protection occurs.
- Check input voltage of R/S/T on driver board.
- if lower than 210V this protection occurs.
- If OK, replace compressor driver board.
Who to ask for: heat pump electrical / inverter.
Certification: Electrical competence; manufacturer-trained heat pump engineer.
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
- Check the input voltage measurement.
Who to ask for: heat pump electrical / inverter.
Certification: Electrical competence; manufacturer-trained heat pump engineer.
On the Activair Pro (AI) R290 6/12/17kW
- Check the input voltage measurement.
Who to ask for: heat pump electrical / inverter.
Certification: Electrical competence; manufacturer-trained heat pump 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 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 34 · Reviewed 23 September 2026
- Trianco Activair Pro Air Source Heat Pump (R290 6/12/17kW) - Installation Operation and Service Manual ↗ · 06/2026 · page 42 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026