Worcester heatslave oil boiler combi thermostat cut out

[Johntheo5]

So, you are saying its generally cycling on and off on the boiler control stat setting (quite normal) but if you shut it down or its a programmed then you find the hi limit stat has locked out the boiler? What temperature is the boiler control stat set to?.
I have a 19 yeard old firebird (non combi) with boiler stat set to 75C which means it cycles on and off beytween 75C and~ 65C, if I measure the flow temp after it shuts down it rises to ~ 90/92C due to having no pump overrun but this has never been a problem as my (and most( hi limit stats are set to operate at 110C to 113C so a long away from this. Its a possibility if you have the control stat setting turned up fully.
Is it happening after just the CH is on or is it also happening after the DHW is on?

 

[villiers1041]

Just heating I believe

 

[Johntheo5]

Ok is it behaving like I said, above?

 

[villiers1041]

i have put another panel and thermostats on and will check it later.

 

[oilhead]

My thought is that the heat store stat and the boiler stat are out of sync, or there is an obstruction in the diverter valve that stops the boiler dispersing its heat. There used to be a similar problem with larger Mistral combis and they produced a mod that consisted of a clamp on button stat that was fitted between in series with the boiler stat on the flow pipe.
Could the flow pipe on a boiler of this age be restricted with scale?

 

[villiers1041]

Changed the diverter valve AGAIN and now still.the same !!
And Changed heat exchanger ,all pipes are clear.
Odd that I have same boiler in my shed that i use for just hit water and that is fine when i change all components over so might do a swap in the summer and see .

 

[Johntheo5]

So
It worked fine for a while
All controls working as they shoukd and hot water and central heating fine , then I turned heating off last night and then checked this morning reset tripped again

I see some models have pump overrun, does this one?. if so can the pump circulate water through the rads or a rad to remove the excess heat or is there a ABV installed?.