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Heating engineer · Brussels and Wallonia
The boiler keeps locking out, or switching on and off
A lockout means the boiler has shut itself down because a check failed: it shows a code or a warning light. If it keeps switching on and off, that's a different problem, often settings or circulation.
The most common causes
A failed ignition
The flame doesn't light or isn't detected: gas supply, ignition electrode, flame sensing.
Low pressure or overheating
Not enough water, or it circulates badly: the boiler shuts down to protect itself.
The flue or condensate
Flue gases or condensate aren't draining properly. In a hard frost, the condensate pipe can freeze if it runs outside.
On and off every few minutes
The boiler is set too powerful for the need, the thermostat is badly placed, or too many radiator valves are closed.
What you can check yourself
- Write down the code on the display: it tells you which check failed (see the error codes below).
- Check the pressure: between 1 and 2 bar with the boiler cold.
- Open your radiator valves: if nearly all are closed, water no longer circulates enough.
- In a hard frost: check whether the pipe running from the boiler outside or to the drain is frozen or blocked.
- Reset once (guide below).
Don't
- Resetting several times in a row: some appliances lock after a few attempts.
- Opening the casing or touching the flue.
- Smell gas? Don't reset: follow our « Smell of gas » page.
Call us if…
- The boiler locks out again after a reset.
- It cuts out often, even if it restarts.
- The code concerns the flue, the flame or the gas.
- It switches on and off every few minutes.
What does a repair cost?
Call-out and diagnosis: €125 excl. VAT. The repair is extra, and you get its price before we start. We usually come within 24 hours (working days) and let you know 1 hour before we arrive.
This advice applies to most boilers. Every appliance has its quirks: if in doubt, your own manual applies, and we're happy to answer on the phone.
Frequently asked questions
My boiler locks out at night: why?
On cold nights, the condensate pipe can freeze if it runs outside. Otherwise, it's often an ignition fault that shows up when the boiler restarts after the night setback. Write down the code and call us.
My boiler fires up every 15 minutes: is that normal?
No. Starting too often wears the boiler out and wastes gas. Usually it's set too powerful for the house, or water circulates badly. Adjusting it on site often solves it.
Find out more
A breakdown, a question? Get in touch.
Call us or message us on WhatsApp. Or leave your number, with a photo of the boiler if you like: we'll call you back.
