P27 on an Ideal Heating HP290: High Pressure Sensor and Low Pressure Sensor Wiring Reversed
Short answer
On an Ideal Heating heat pump, P27 means: High Pressure Sensor and Low Pressure Sensor Wiring Reversed. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: High Pressure Sensor and Low Pressure Sensor Wiring Reversed.
Part involved: pressure sensor wiring.
Likely causes:
- HP and LP sensor connectors cross-connected; outdoor PCB.
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 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.
What the engineer will check
- Check wiring per diagrams; correct; replace outdoor 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 109 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026