ER 04 error code
ER 04 — Primary circuit has insufficient water or flow
What does Biasi Activ A condensing boiler ER 04 mean?
Biasi Activ A documentation identifies ER 04 as “Primary circuit has insufficient water or flow”. Confirm the exact model because similarly numbered codes can have different meanings on other Biasi control generations.
The code identifies the condition detected by the product; it does not always identify the failed component on its own. Confirm the full code and exact model before ordering parts or attempting a reset.
The Biasi Activ A condensing boiler ER 04 error code indicates biasi Activ A documentation identifies ER 04 as “Primary circuit has insufficient water or flow”. Confirm the exact model because similarly numbered codes can have different meanings on other Biasi control generations. This guide explains what the code means, the symptoms and likely causes, the checks that are safe to make, and when to stop and arrange an authorised repair.
Symptoms you may notice
The boiler detects inadequate circulation, pressure or an excessive temperature condition.
Common causes
Low pressure, air lock, closed valve, blocked circuit, pump fault, heat-exchanger restriction or inaccurate sensing.
Before you start troubleshooting
Use the display, rating label or product menu to confirm the exact model. Similar-looking codes can have different meanings across product generations and regions.
- Record the complete code before switching the equipment off.
- Check only user-accessible controls, filters and external connections described in the manual.
- Do not open gas, refrigerant, combustion or electrical compartments.
Troubleshooting steps
Check only accessible system pressure and valves. An engineer should test circulation, pump operation, venting, sensors and the heat exchanger.
Can you fix this error code yourself?
This fault is not intended for user repair. Do not remove covers or test internal components; record the code and contact an authorised technician.
A successful reset is not proof that the underlying issue is fixed. If ER 04 reappears, note when it happens and give that information to the service engineer.
Reset instructions
Use the reset control only where the exact model instructions show that the displayed fault permits it. If the code returns, do not keep resetting the boiler; stop and arrange professional diagnosis.
Applicable products and models
Activ A condensing boilerActiv A 25C; 30C; 35C; 12OV; 15OV; 20OV; 25OV; 18S; 25S; 30SLegacy and supportedWhen to contact a professional
Contact a qualified Biasi engineer if ER 04 returns, prevents operation, involves flame or overheating, or requires internal testing.
Frequently asked questions
What does Biasi Activ A condensing boiler ER 04 mean?
Biasi Activ A documentation identifies ER 04 as “Primary circuit has insufficient water or flow”. Confirm the exact model because similarly numbered codes can have different meanings on other Biasi control generations.
Can I fix Biasi Activ A condensing boiler ER 04 myself?
This code is not classed as user-fixable. Record it and arrange authorised diagnosis rather than opening the product.
Should I reset the product after code ER 04?
Use the reset control only where the exact model instructions show that the displayed fault permits it. If the code returns, do not keep resetting the boiler; stop and arrange professional diagnosis.
When should I arrange a repair?
Contact a qualified Biasi engineer if ER 04 returns, prevents operation, involves flame or overheating, or requires internal testing.