E0 on an Ideal Heating HP290: No Water Flow, through Outdoor Unit, 10 times in succession
Short answer
On an Ideal Heating heat pump, E0 means: No Water Flow, through Outdoor Unit, 10 times in succession. 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, 10 times in succession.
Part involved: primary pump / flow switch.
Likely causes:
- Pump stuck in standby/blocked/running dry (pump feedback 0/2/80/85/90/95%); ball valve closed; flow and return cross-connected; dirty filters/strainers; system not full or not vented; outdoor PCB DIP switches wrong; faulty flow switch or wiring; pump supply/low-voltage wiring; supply voltage outside 170-253 V AC; outdoor PCB.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Manual reset: After root cause corrected, turn power off and on to clear (p.97).
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 pump feedback (section 5.8.7); check ball valve, pipe orientation, strainers, fill/vent; check DIP switches; test flow switch continuity; check pump 240 V and PWM wiring; replace pump/flow switch/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 97 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026