E8 on an Ideal Heating HP290: No Water Flow, through Outdoor Unit
Short answer
On an Ideal Heating heat pump, E8 means: No Water Flow, through Outdoor Unit. 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 Water Flow, through Outdoor Unit.
Part involved: primary circuit.
Likely causes:
- Isolation valves closed; strainers blocked; system pressure outside 1-1.5 bar; air in 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
- 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
- Check isolation valves open, strainers clean, pressure 1-1.5 bar, bleed air; power cycle at rotary isolator (1 min); if unresolved follow E0 flowchart 9.1.2.
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 100 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026