H0 on an Ideal Heating HP290: No connection Outdoor PCB to Indoor PCB
Short answer
On an Ideal Heating heat pump, H0 means: No connection Outdoor PCB to Indoor PCB. 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: No connection Outdoor PCB to Indoor PCB.
Part involved: outdoor-indoor comms cable.
Likely causes:
- Three-way comms wiring outdoor PCB to indoor control box, or control box to indoor PCB, incorrect (T1-T1, T2-T2, X/HA-X/HA, X/HB-X/HB); indoor PCB or outdoor PCB faulty.
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
- 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. If the fault clears after the installer-approved restart via the controller and does not return, note it for the next service; if it returns, call an engineer.
What the engineer will check
- Check comms wiring terminations; replace indoor PCB then 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.
What you might notice
Sources
- HP290 Monobloc Heat Pump System - Installation & Maintenance (UIN 240080 A09) ↗ · UIN 240080 A09 · page 101 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026