E0 on a Worcester Bosch Bosch Compress 2000 AWF: Alarm table: Water flow failure (water flow failure 3 times) / Troubleshooting table: Flow switch error (E8 displayed 3 times; to be seen together with E8)
Short answer
On a Worcester Bosch heat pump, E0 means: Alarm table: Water flow failure (water flow failure 3 times) / Troubleshooting table: Flow switch error (E8 displayed 3 times; to be seen together with E8). 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: Alarm table: Water flow failure (water flow failure 3 times) / Troubleshooting table: Flow switch error (E8 displayed 3 times; to be seen together with E8).
Part involved: flow switch.
When it shows: Water flow failure (water flow failure 3 times).
Likely causes:
- Flow switch circuit short-circuited or open; insufficient water flow rate; faulty flow switch opening/closing continuously; system pressure losses too high for unit circulator.
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.
Resetting itself: no.
Manual reset: Manual 13.2: switch the unit off and on again to reset the safety device; if reset fails contact dealer. Manual 11.4 warns repeated resets can cause irreversible damage.
What you can check
- Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
- Check the heating system pressure gauge reading (Bosch guidance is typically 1-2 bar when cold); report low pressure to your installer.
- Manual 13.2: one off/on restart may be tried; if the code returns, stop and call an engineer - repeated resets can damage the unit.
What the engineer will check
- Check flow switch wiring and operation; verify flow rate, strainer, air, valves and pump head; overhaul system hydraulics if losses too high.
Who to ask for: heat pump installer / heating engineer.
Certification: None specific for hydraulic checks; MCS-certified installer recommended for system changes.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- Keeps stopping / cutting out on the Bosch Compress 2000 AWF (R32 all-in-one monobloc): 1 report
Sources
- Installation and operating instructions Compress 2000 AWF CS2000AWF 4-30 R-S/T ↗ · 6721859133 (2025/10) · page 128; 135 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026