THE SHORT ANSWER
WHERE THE LINE IS
Resetting and topping up are householder jobs. Anything behind the case is not, and there is no grey area in between.
No tools, no gas work
Press reset
Once, held about three seconds
Top up pressure
On the filling loop, to about 1.5 bar cold
Check the thermostat
Batteries, and that it is calling for heat
Check the fused spur
And the consumer unit
Photograph the code
Before you clear it
Thaw the condensate
Warm water on the outside pipe
These are not DIY
You smell gas
Call 0800 111 999 before anything else
Removing the case
Gas Safe work, and it voids the warranty
Repeated lockouts
The boiler is telling you something real
Water inside the case
Turn it off at the spur and call
Black or sooty marks
Around the boiler or the flue
Pressure drops daily
A leak, not a top-up job
BEFORE YOU HIT RESET
1
Look at the gauge on the front. If it is under about 1 bar the boiler will lock out on low pressure and no amount of resetting will fix it until you top it up on the filling loop. If it keeps dropping, you have a leak or a failed expansion vessel and that needs an engineer.
2
Check another gas appliance lights, and check the fused spur and the consumer unit. It sounds obvious, and it is genuinely one of the more common reasons we get called out to a boiler that is not broken.
3
The code on the display is the most useful thing you own when you call someone. Resetting wipes it. Photograph it first, then reset. If you have to call us, that code often tells us the part to bring.
WHAT HAPPENED AFTER
It fired up and has stayed on
It fired up and went again within the hour
It will not light at all
It only happens in cold weather
COMMON QUESTIONS
How do I reset my boiler?
How many times can I reset a boiler?
Why does my boiler keep locking out?
Where is the reset button?
Is it safe to reset a boiler myself?
The boiler resets but stops again after an hour. What now?
BEFORE YOU GO
More of the same, written by the engineers who do the work.