- Heat pumps
- Air-to-water heat pump
E8
Junkers Bosch E8 on a heat pump: water flow fault detected
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Medium
Quick answer
On the Bosch Compress 2000 AWF, E8 signals a water flow fault: not enough water is moving through the unit. Check the gauge reads above 1 bar and the shut-off valves are open, then call a technician if it returns.
Safety first
Stop and check this first
- The Compress 2000 AWF uses R32 refrigerant and has capacitors that hold voltage after disconnection; do not remove service panels, that work belongs to a qualified technician.
- Resetting the alarm again and again without fixing the cause can damage the system irreversibly, Bosch warns.
Safe checks you can perform
- Read the alarm in the service menu
- Gauge pressure above 1 bar
- Visible shut-off valves fully open
- One reset by switching off and on
Leave these tasks to a qualified professional
- Do not attempt this professional task: Bleed air and clean the water filter
- Do not attempt this professional task: Check pump, expansion vessel and pressure losses
- Do not attempt this professional task: Electrical check of fuses and flow meter
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Bleed air and clean the water filter
What they doThe technician opens the air vent, removes air from the circuit, cleans the water filter and sets the pressure between 1.5 and 1.8 bar, as the annual maintenance in the manual describes.
They must show youthe final gauge pressure and the cleaned filter.
In writingthe pressure before and after, and the condition the filter was in.
Check pump, expansion vessel and pressure losses
What they doThe installer confirms the pump speed is at maximum, the expansion vessel is intact and the hydraulic resistance of the circuit is within what the pump can move.
They must show youthe measured flow rate against the manufacturer minimum and the expansion vessel pre-charge.
In writingthe measured values and any pump settings that were changed.
Electrical check of fuses and flow meter
What they doA qualified professional, with the unit isolated and after waiting 10 minutes for the capacitors to discharge, checks the pump and board fuses, the back-up heater supply and the flow meter wiring.
They must show youthe fuses tested and the unit alarm history.
In writingwhat was found, any replaced parts and why.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Read the alarm in the service menu
- Who:
- you, from the user interface.
- How:
- when the active alarm symbol shows, open the menu and its service information page (INF. DE SERVICIO on the Spanish interface) to see the code. Also note whether the unit was heating the house, making hot water or defrosting.
- Result that matters:
- the code confirmed along with the operating mode it appeared in.
- If it is E8:
- carry on with pressure and valves.
- If E0 shows:
- E8 has already happened three times, so contact the technician straight away.
- Evidence to keep:
- photo of the service information screen.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
Gauge pressure above 1 bar
- Who:
- you, looking at the pressure gauge.
- How:
- read the pressure with the system cold. Bosch says it must be above 1 bar and should be checked regularly, since hot water shows a slightly higher reading.
- Result that matters:
- a reading above 1 bar when cold.
- If it is lower:
- stop resetting and ask the technician to top up and find the leak.
- If it is fine:
- check the shut-off valves.
- Evidence to keep:
- photo of the gauge with its reading.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
Visible shut-off valves fully open
- Who:
- you, no tools needed.
- How:
- find the shut-off valves of the water circuit that you can see and check each handle is in the open position. Do not take the filter apart: cleaning it is listed among the qualified technician tasks.
- Result that matters:
- every accessible valve completely open.
- If one was half open or shut:
- open it fully and wait a few minutes before resetting.
- If all were open:
- the cause is more likely air, the filter or the pump.
- Evidence to keep:
- photo of each valve in its position.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
One reset by switching off and on
- Who:
- you, from the interface.
- How:
- the manual says to reset the safety device by switching the unit off and on again once the cause is removed. Do it only once, because Bosch warns that repeated resets can cause irreversible damage.
- Result that matters:
- learning whether the unit starts and keeps its flow after the fixes above.
- If it runs without showing E8 again:
- note what you corrected.
- If the reset fails or E8 comes back:
- contact technical service, as the manual asks.
- Evidence to keep:
- time of the reset and whether the code reappeared.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- Junkers
- Product type
- Air-to-water heat pump
Known code variants
- AEG E8
- AEG E822
- AEG hob E8
- Baxi heat pump E8
- Baxi HP40 E8
- Baxi HP50 E8
- Beko BM1WU E8 code
- Beko lavadora E8
- Beko washer E8
- Beko washing machine E8 not taking water
- Bosch Compress E8
- Bosch E8 caudal de agua
- Bosch E8 water flow
- Bosch heat pump E8
- código E8 Beko BM1WU
- Compress 2000 AWF E8
- CS2000AWF E8
- E08
- E 8
- E822
- E8xx
- E:8
- error E8 aerotermia Bosch
- Gree E8
- Junkers E8
- lavadora Beko E8 no coge agua
- placa AEG E8
What it means
The Compress 2000 AWF manual (Bosch, 2025) lists E8 as a water flow error; it is displayed after occurring three times and can be reset after a few minutes. If E8 comes up three times, the unit moves on to E0, a flow meter error. Bosch suggests checking shut-off valves, the water filter, air in the system, pressure above 1 bar, pump speed, the expansion vessel and the hydraulic resistance of the circuit. E8 alone does not confirm that the flow meter or pump has failed. Only the Spanish edition of the manual was used.
Warnings and stop conditions
- Mediumeditorial warning
The Compress 2000 AWF uses R32 refrigerant and has capacitors that hold voltage after disconnection; do not remove service panels, that work belongs to a qualified technician.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
- Loweditorial warning
Resetting the alarm again and again without fixing the cause can damage the system irreversibly, Bosch warns.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
Symptoms and causes
Probable causes · in order
- Circuit shut-off valves not fully openCommon
The first measure Bosch gives for E8 is to check that every shut-off valve in the water circuit is completely open.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
- Low pressure, air or a dirty water filterCommon
With less than 1 bar, air trapped in the system or a clogged water filter, the flow the unit measures drops below what it needs.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
- Pump head too low for the systemPossible
If the circuit resistance is too high for the pump, or its speed is not set to maximum, water does not circulate strongly enough.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
- Fuses or back-up heater during defrostLess common
When E8 appears during defrost, Bosch asks for the back-up heater supply to be checked and for the pump and board fuses to be intact.
Evidence: Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
Virtual technician
Does E8 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Bosch Compress 2000 AWF (CS2000AWF 4-30 R-S/T), instrucciones de montaje y uso 6721860781
Bosch Home Comfort (Junkers Bosch España) · 2025 · manual
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