Heat pumps · Error codes · Cool Energy
AL137Cool Energy · inverTech (R410A, Carel control)
AL137 on a Cool Energy inverTech: Flow switch alarm
Short answer
On a Cool Energy heat pump, AL137 means: Flow switch alarm. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Flow switch alarm.
When it shows: Low flow detected by flow switch on the return pipe.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Clears when water flow is restored (manual p.33).
What you can check
- Read and note the code shown on the controller display, then contact your installer or service engineer.
- Check the heating system pressure gauge reading against the value in your handover documents (manufacturer commissioning values: typically 1-2 bar) and that the filling loop is closed.
What the engineer will check
- Check water flow rate/flow switch and wiring.
- Check strainer/magnetic filter for blockage.
- Vent air from the system.
- Check circulating pump operation and pipe sizing.
- Check valves/zone valves are open.
Who to ask for: heating / plumbing heat pump installer.
Certification: None specific (unvented/G3 if cylinder work).
What you might notice
Sources
- Cool Energy inverTech Monoblock Series Heat Pump Water Heaters - Installation and Users Guide v6.6 (2020) ↗ · Version 6.6 · page 32 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026