Overview
D.60 on a Vaillant ecoTEC Plus indicates that a safety temperature cut-out has been reached and the boiler has gone into protective shut-down. In practice this means the boiler’s overtemperature protection (safety temperature limiter or related cut-out) has tripped — often after repeated high-temperature events — and the unit is locked out to prevent damage or unsafe operation. This is a potentially serious condition because it is a protective response to overheating. Common underlying reasons include poor circulation (failed pump, closed or partially closed valves, airlocks), blocked heat exchanger or flue, scale/build-up restricting flow, faulty flow/return temperature sensors or their wiring, or a defective safety thermostat or PCB. Because the cause can involve gas, electrical parts, or internal components, most diagnostic and repair tasks should be done by a qualified Gas Safe (or equivalent) engineer rather than attempting internal repairs yourself.
Possible Cause: Number of safety temperature cut off
Troubleshooting Steps
Safety first: If you smell gas, leave the building immediately, do not operate electrical switches, and call your gas emergency number. If you suspect carbon monoxide (unusual smells, headache, dizziness, soot, or pilot lights behaving oddly) turn the boiler off, ventilate the area, get everyone out of the building and call an emergency service/engineer. Do not open the boiler or attempt gas/electrical repairs yourself.
Initial checks a homeowner can safely do:
1. Switch the boiler off at the main power switch and allow it to cool for at least 20–30 minutes. Do not repeatedly reset the boiler. One controlled reset attempt is reasonable after cooling.
2. Check the boiler pressure gauge. Normal pressure is typically around 1.0–1.5 bar when cold. If pressure is very low, that can cause circulation issues — you can top up pressure using the filling loop if you know how and have done it before. If unsure, stop and call an engineer.
3. Ensure the gas isolator cock (on-site) and the boiler gas valve are open. Confirm the mains power has not tripped.
4. Listen/feel for the heating pump when the boiler calls for heat (pump should run and pipes should warm). If pump is silent and you have radiators cool, there may be a circulation failure or pump blockage/airlock.
5. Bleed radiators to remove any trapped air which can reduce circulation.
6. Check the external flue termination (outside) for obvious blockages (birds’ nests, debris) and check condensate pipe for frost/blockage in cold weather.
7. Note any other displayed fault codes or behavior (whether it happens on heating, hot water, after long run, immediately on start, etc.).
How to attempt a single reset safely:
1. After the boiler has cooled and you have completed the initial checks, locate the reset/fault-clear key on the control panel and press it once per the manual instructions. Wait and watch the boiler through a normal start cycle. Do not repeatedly reset if the fault returns.
2. If the code clears and the boiler operates normally for a sustained period, monitor pressure, pump noise, and radiator temperatures. If the problem reappears, stop using the boiler and call an engineer.
When to call a professional and what to tell them:
1. Call a Gas Safe registered engineer if D.60 reappears, if you cannot restore normal pressure or circulation, if you hear unusual noises, notice leaks, or if other fault codes appear. Do not allow an unqualified person to work on gas or sealed electrical components.
2. Provide the engineer with the exact code (D.60), when it occurs (during hot water, during heating, after long run, on start-up), boiler model/serial, current system pressure, how many reset attempts you tried, and any other symptoms (noisy pump, cold radiators, blocked flue, recent plumbing work).
What the engineer will likely check/perform (for information only):
- Read full fault history and log from the boiler PCB.
- Inspect flow and return temperature sensors (NTC thermistors), their wiring and connectors, and measure sensor resistances.
- Test the primary pump for operation, blockages or airlocks and check service valves/devices for correct position.
- Inspect heat exchanger for blockage, scale or damage and check condensate drainage.
- Test the safety temperature limiter (STB), other safety cut-outs and the PCB for faults.
- Check for restricted flue or flue gas temperature limiter activation and test gas valve behaviour if necessary.
Do not attempt internal electrical or gas component replacement yourself. If the boiler has tripped on overtemperature multiple times (D.60), it indicates a systemic issue that needs professional diagnosis and repair to ensure safe operation.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Vaillant EcoTEC Plus Regular Gas Boiler.