E12 on a Trianco heat pump: Syst1: Low Pressure Prot
Short answer
On a Trianco heat pump, E12 means: Syst1: Low Pressure 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: Syst1: Low Pressure Prot.
Part involved: pressure switch / compressor discharge-suction.
Likely causes:
- The low-voltage (low-pressure) switch of the system is disconnected.
On the Activair High Temperature R290 (5/9/15/22kW)
The manual says: LP Protection.
Part involved: pressure switch / compressor discharge-suction.
Likely causes:
- LP switch is open.
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
The manual says: LP Fault.
Part involved: pressure switch / compressor discharge-suction.
Likely causes:
- The low-pressure switch is broken.
On the Activair Pro (AI) R290 6/12/17kW
The manual says: LP Fault.
Part involved: pressure switch / compressor discharge-suction.
Likely causes:
- The low-pressure switch is broken.
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 debris/snow and has its required clearances.
What the engineer will check
On the Activair Commercial R290 50kW (FG9550)
- Inspect System 1 pressure switch and refrigerating circuit for any failure.
Who to ask for: refrigeration.
Certification: F-gas certified refrigeration engineer (REFCOM or equivalent).
On the Activair High Temperature R290 (5/9/15/22kW)
- Check whether showing the error after unit shutdown.
- Measure the suction pressure when the unit is running.
- Detect EEV step, discharge pressure, inlet/outlet water, discharge and suction temp.
- Release all the gas of the system and refill refrigerant according to the nameplate.
Who to ask for: refrigeration.
Certification: F-gas certified refrigeration engineer (REFCOM or equivalent).
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
- Check the pressure switch and cold circuit.
Who to ask for: refrigeration.
Certification: F-gas certified refrigeration engineer (REFCOM or equivalent).
On the Activair Pro (AI) R290 6/12/17kW
- Check the pressure switch and cold circuit.
Who to ask for: refrigeration.
Certification: F-gas certified refrigeration engineer (REFCOM or equivalent).
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 34 · 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