P1 on an Ideal Heating HP290: High Pressure Switch Operated
Short answer
On an Ideal Heating heat pump, P1 means: High Pressure Switch Operated. 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 Switch Operated.
Part involved: high pressure switch.
Likely causes:
- Often secondary to no water flow (E8/E0); HP switch wiring to inverter disconnected; refrigerant pressures >3.5 MPa; blocked/damaged pipes or filter to HP switch; EEV not operating; inverter PCB.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Manual reset: Lockout reset required (p.107).
What you can check
- Note the code or fault message shown on the controller/Halo and when it appeared; check the heat pump's isolator and consumer-unit breaker are on. Read the heating system pressure gauge (the HP290 manual cites 1-1.5 bar) and report it; check the filling loop is closed.
What the engineer will check
- If occurred with E8/E0 follow 9.1.2; check HP switch wiring; check P1/P2 pressures; check pipes/filter; reset lockout and check EEV; replace HP switch or inverter PCB.
Who to ask for: Heat pump engineer competent with R290 (A3, highly flammable); refrigerant-circuit work requires Cat I/II F-gas plus City & Guilds 6187-21 or equivalent (I&M p.93 warning).
Certification: F-gas Cat I/II + C&G 6187-21 (R290) for refrigerant work; electrical work by competent person.
Sources
- HP290 Monobloc Heat Pump System - Installation & Maintenance (UIN 240080 A09) ↗ · UIN 240080 A09 · page 107 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026