Buderus 0Y 276 Fault Code: Causes, Fixes & Repair Costs
What does the Buderus 0Y 276 fault code mean?
Fault code 0Y 276 tells you that the boiler's flow temperature sensor has recorded water temperatures above 95°C, prompting the boiler to shut itself down as a safety measure. The broader 0Y code class means the actual flow temperature has climbed higher than the target setpoint, and the boiler cuts out to protect both itself and your heating system from dangerous overheating. In some cases this can happen without a genuine component failure — for instance, if several thermostatic radiator valves (TRVs) are closed at the same time, water has nowhere to circulate and rapidly overheats at the heat exchanger.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Thermostatic radiator valves all closed simultaneously Common
If most or all TRVs in your home are shut at the same time — common overnight or when rooms are unused — the pump has nowhere to push the heated water. The flow temperature rockets and the boiler cuts out on overheat. This is the simplest cause and requires no parts, just opening a few valves.
- Faulty or poorly seated flow temperature NTC sensor Common
The NTC thermistor monitors water temperature leaving the heat exchanger. If the sensor has drifted out of position, corroded, or failed, it can send exaggerated temperature readings to the control board, triggering a false 0Y 276 lockout even when the water is at a perfectly safe temperature.
- Circulation pump seized or underperforming Sometimes
A pump that has seized, lost impeller speed, or has a blocked volute cannot move water around the system quickly enough. Heat builds up at the heat exchanger, the flow temperature climbs above 95°C, and the boiler shuts down. Buderus service function t03 can be used by an engineer to test pump operation directly.
- Safety thermostat tripped or faulty Sometimes
A separate high-limit safety thermostat monitors flue gas and heat exchanger temperatures. If it has tripped due to a genuine overheat event, or has failed in a way that signals overheat even when temperatures are normal, it will hold the boiler in lockout.
- Faulty PCB (control board) Rare
If the control board develops a fault — through voltage surges, moisture ingress, or component failure — it can misinterpret sensor data or fail to switch the burner off at the right time, causing genuine or apparent overheating. Signs include burn marks, a faint burning smell, or oxidised connectors on the board.
How to fix it
- Check that your radiator TRV valves are open DIY safe
Walk around the property and make sure thermostatic radiator valves are not all turned to the closed or frost-protection position. Open several radiators fully so the pump has adequate flow paths. This costs nothing and resolves the fault surprisingly often.
- Check and top up system pressure if needed DIY safe
Look at the boiler pressure gauge. It should read between 1.0 and 1.5 bar when cold. If it is below 1 bar, use the filling loop to top it up — refer to your boiler manual for the location. Low pressure reduces water flow and can contribute to localised overheating.
- Reset the boiler DIY safe
Press and hold the Reset button for around 5 seconds, or switch the boiler off at the mains for 15 seconds and switch it back on. Do this no more than two or three times. If the fault clears and the boiler fires successfully, monitor it over the next hour. If 0Y 276 returns, move on to the steps below — repeated resets without fixing the root cause will not help and could mask a genuine problem.
- Have a Gas Safe engineer test the NTC flow temperature sensor Gas Safe engineer
An engineer will disconnect the NTC thermistor and test its electrical resistance with a multimeter at known temperatures. A sensor reading out of the expected resistance range indicates it has failed and needs replacing. This is a relatively inexpensive repair and one of the most common fixes for this fault code.
- Have the circulation pump inspected and tested Gas Safe engineer
The engineer can run Buderus service function t03 to observe pump behaviour through the boiler's own diagnostics. They will check the pump's connection cable, listen for signs of a seized impeller, and verify the pump is delivering adequate flow. A seized pump can sometimes be freed; a worn or failed unit will need replacing.
- Have the safety thermostat checked Gas Safe engineer
If the pump and NTC sensor are confirmed healthy, an engineer should check whether the high-limit safety thermostat has tripped or failed. A tripped thermostat may simply need resetting; a faulty one will need replacement.
- Have the PCB inspected as a last resort Gas Safe engineer
If all other components check out, the engineer should examine the control board for signs of heat damage, burnt components, oxidised connectors, or moisture. PCB replacement is the most expensive outcome for this fault, so a methodical engineer will rule out cheaper causes first. Always supply your exact Buderus model designation when sourcing a replacement board.
Parts you may need
- NTC flow temperature sensor (thermistor) · from £28
- Circulation pump (Grundfos or equivalent OEM) · from £145
- High-limit safety thermostat · from £35
- Buderus PCB / control board · from £320
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £90–£380, depending on the underlying cause.
Frequently asked questions
Can I fix Buderus fault code 0Y 276 myself?
The only homeowner-safe actions are opening closed TRV valves, topping up system pressure via the filling loop, and resetting the boiler a couple of times. If those steps do not clear the fault, the cause is almost certainly a failed sensor, pump, or internal component that must be diagnosed and repaired by a Gas Safe registered engineer. Do not attempt to access internal components yourself.
Why does 0Y 276 keep coming back after I reset the boiler?
A recurring 0Y 276 fault means the underlying cause has not been addressed. The most likely culprits are a degraded NTC flow temperature sensor sending false high readings, a circulation pump that is losing efficiency, or TRVs that are restricting flow across large parts of the system. Each reset without a fix puts extra thermal stress on the boiler, so book an engineer rather than continuing to reset.
How much does it typically cost to repair a Buderus 0Y 276 fault in the UK?
Most people with this fault end up paying somewhere between £90 and £380 all-in. An NTC sensor replacement including labour usually costs around £80–£180, while a circulation pump swap typically runs £150–£350 depending on your region and the pump model. If the PCB turns out to be the cause, replacement costs are significantly higher — often £450–£700 — but this is the least common outcome. Engineers in London and the South East generally sit at the top of these ranges, while the North of England and Wales tend to be 10–20% cheaper.
Is it safe to keep using my boiler after seeing fault code 0Y 276?
No — the boiler will have already shut itself down as a safety measure, so it will not produce heat or hot water until the fault is resolved. Do not try to force it back into operation through repeated resets if it keeps locking out. The fault indicates water in the system has reached or approached 95°C, which is genuinely dangerous. Get it looked at promptly.