Heat pumps · Error codes · Lailey and Coates Ltd
P15Lailey and Coates Ltd · Lailey & Coates LCM monobloc (LCM-06/09/17)
P15 on a Lailey and Coates Ltd Lailey & Coates LCM monobloc: High Pressure Protection fault
Short answer
On a Lailey and Coates Ltd heat pump, P15 means: High Pressure Protection fault. 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: High Pressure Protection fault.
Likely causes:
- Flow restrictions within the wet system.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
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.
- Check the outdoor unit/air grilles are not blocked by debris, leaves or snow.
What the engineer will check
- Check there is no air in the system.
- Check no blockages in any pipework.
- Check diverter valves are set correctly and not blocking flow.
- Check all pumps in the system are working and water flow rate is sufficient.
- Check water flow first (high pressure is often caused by low flow).
- Check refrigerant pressures/temperatures with gauges (F-gas qualified).
- Check for refrigerant leak or blockage, EEV operation and pressure switches/transducers.
Who to ask for: refrigeration / F-gas heat pump engineer.
Certification: F-gas certification (Category I) for refrigerant circuit work.
What you might notice
Sources
- Lailey & Coates Monobloc Air Source Heat Pumps - Installation & Maintenance Manual (LCM-06 / LCM-09 / LCM-17) ↗ · page 18 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026