Worcester Bosch fault code 2964 means the boiler has detected that the water flow rate through its heat exchanger is too low. The code is used on several Worcester Bosch ranges, including the Greenstar 1000, Greenstar 2000, Greenstar 8000 Life and Condens 7000 WP manuals checked for this guide.
Low flow through a working boiler can cause temperatures to rise too quickly, so the appliance may pause operation rather than continue under conditions it cannot accept. Keep the casing closed, record the full display and arrange a repair if the code remains or returns.
What does Worcester Bosch fault code 2964 mean?
The heat exchanger transfers heat from the boiler into the water circulating around your heating system. That water needs to move at an acceptable rate. Code 2964 is Worcester Bosch’s way of reporting that the flow rate through the heat exchanger is too low.
Worcester Bosch lists 2964 as a blocking fault in the Greenstar 1000 and Greenstar 2000 documentation. A blocking fault can interrupt operation while the unwanted condition is present. It should not be bypassed or treated as permission to keep restarting the boiler.
The code tells an engineer which condition the boiler detected. It does not identify one guaranteed failed part.
What can cause a low flow rate through the heat exchanger?
Manufacturer service information points engineers towards several areas that can affect flow. These include whether the system is filled, whether the heating circuit is open, whether the pump is operating correctly and whether the relevant temperature sensor is correctly positioned and reporting properly.
Those possibilities require different checks, and several are inside the appliance. Code 2964 does not automatically mean that the pump has failed, that the heat exchanger is blocked or that a sensor needs replacing.
For a homeowner, the safest approach is to record what is happening externally rather than trying to determine the internal cause.
What symptoms might appear with code 2964?
The boiler may stop during a heating or hot-water request. Radiators may fail to warm, hot water may be interrupted, or the appliance may attempt to run and then pause. The precise behaviour depends on the model and system layout.
Useful details to note include:
- the complete code and any other symbols on the display;
- whether heating, hot water or both were being requested;
- whether any radiators began to warm before the boiler stopped;
- the system pressure visible on the boiler display or gauge;
- any obvious external water leak;
- whether the problem appeared after legitimate work on the heating system.
Do not touch hot pipework. A display photograph and a short description of the symptoms will help the engineer without disturbing the appliance.
Is 2964 the same as low boiler pressure?
No. A heating system with insufficient water or pressure can affect circulation, but Worcester Bosch gives 2964 the specific meaning of insufficient flow through the heat exchanger. Low-pressure faults have their own codes on applicable boilers.
Look at the pressure only from the normal display or gauge. Do not assume that topping up will clear 2964. If the pressure is outside the range stated in your exact user manual, follow only the homeowner procedure given for that model or arrange help.
Can I reset a Worcester Bosch 2964 fault?
Check the user manual for your exact boiler. If it permits a normal user reset, you may try one reset from the front controls. If 2964 remains or returns, stop resetting and arrange a repair.
A reset cannot restore circulation if a pump, valve, sensor or another part of the system needs attention. Repeated resets can make the boiler run briefly without making it reliable.
Do not remove the casing, test the pump, unplug sensors, adjust internal valves or test wiring. These are not homeowner checks.
Does the code apply to every Worcester Bosch boiler?
No. Fault codes must be matched to the boiler model. We confirmed 2964 in Worcester Bosch documents for the Greenstar 1000, Greenstar 2000, Greenstar 8000 Life and Condens 7000 WP. Other ranges may use different codes or wording.
Find the model on the boiler’s external label or in its paperwork and consult the matching user manual. Do not identify the model from the appearance of the display alone.
Is a 2964 fault dangerous?
The code means the boiler has detected inadequate flow through the heat exchanger and may have paused operation. Do not bypass that response or keep forcing the appliance to run.
Code 2964 does not itself mean that gas is leaking. If you smell gas, suspect carbon monoxide or a carbon monoxide alarm sounds, treat that as an emergency: avoid flames and electrical switches, open doors and windows, leave the property if necessary and call the National Gas Emergency Service on 0800 111 999. Seek urgent medical help if anyone feels unwell.
What will an engineer check?
A Gas Safe registered engineer can confirm the model, review the fault history and follow the correct Worcester Bosch service procedure. Depending on the system, this may include assessing water circulation, system condition, pump operation, valves and the temperature-sensor information used by the boiler.
The engineer can then correct the actual reason for the low-flow condition. This avoids replacing a pump or sensor simply because it appears on a list of possible causes.
What should I do now?
- Photograph the complete display.
- Note whether heating, hot water or both stopped.
- Record the visible system pressure without opening the boiler.
- Look for an obvious external leak.
- Try one normal reset only if your model’s user manual permits it.
- If 2964 remains or returns, book a boiler repair.
Get your boiler flowing and working again
Book Incredaboil’s fixed-price boiler repair for a clear price and a visit focused on fixing the 2964 fault.
Worcester Bosch 2964: quick answers
What does code 2964 mean?
It means the boiler has detected that the flow rate through the heat exchanger is too low.
Does 2964 definitely mean the pump has failed?
No. Pump operation is one possible area for an engineer to check, but the code does not prove that the pump is faulty.
Should I top up the boiler?
Not solely because 2964 is displayed. Check the visible pressure and follow only the instructions for your exact model if it separately shows low pressure.
Can I keep resetting the boiler?
No. If one reset permitted by the user manual does not clear the code, or the code returns, arrange a repair.