sime boiler over heating

[delstar]

can anyone please help me out with possible reasons why my friendly format 80e boiler would activate the overheat cut out and how bad this is.
should i just leave it to cool then go again or will i have to find the cause.
it seemed to be working ok today today then stopped working this evening.

any help would be appreciated no matter how basic

thanks

 

[glasgowgas]

first thing i`d look at would be pump

then restrictions in flow and return pipework

then heat exchanger temps

 

[Agile]

These boilers are not very friendly!

There can be several causes. Knowing if its on heating , or DHW, or both would help.

On DHW only then a blocked plate HE would be most likely. On CH only then a failed sensor is also likely.

If you want to see if you can fine the cause then measuring the resistance of sensors with boiler cold seems an easy start.

Tony