combi keeps locking out

[loafer]

halstead ace keeps locking out. initially just on heating but now also on dhw. Have reset numerous times on button underneath boiler but to no avail.
also burner cuts in and out on dwh supply causing showering to be ???annoying as water runs from lukewarm to decidedly chilly.

cold water pressure feed seems low even tho direct mains fed
boiler gets mentally hot... is it emergency cut off????
system seems a little sludgy could do with a flush out but is this the likely cause?
system has been bled of air
towel rail permanently open fully as bypass
pressure gauge shows system running at optimum cold at .9 running at 1.1 bar.

bolier reputedly only 6 years old and serviced 18 months ago.

totally bemused but then am only a novice plumber not a central heating engineer any suggestions gratefully appreciated.

moved to s yorks 4 months ago problem only apparent last week... only ch engineers i know live in london. diagnostics??? b4 i get ripped off

ta
loafer

 

[corgiman]

porbably the central heating and domestic hot water themisters, they are always going on these

 

[loafer]

ahaaaaaaaaaaaaa.... corgi fella came round and discovered that the fibrous sheet insulation on the front face of the combustion chamber had become detached and was obstructing burner. answer was to cut a new piece and seure with heat proof sticky.
central heating ok now but dhw keeps locking out after 5 mins or so... i.e whenever running bath or shower.
at least we aint shiverin and as long as we dont languish in the shower we wont stink.

problem with cold water pressure has been solved also. the water authority stop tap was locked at a 1/4 open and gas mans lad tried to open by closing and opening repeatedly only to completely seize the damn thing in the closed position. rang yorks water and they suggested it was a problem in my system to which I replied cant be, my stop tap is functioning properly and only 3 inches from the drain cock which when fully opened only delivered a trickle then nothing at all. Cheecky sods!!! still after pretending to have an infant in the house and telling them that me and my partner were both working the following day and the child minder was booked etc they agreed to fix the next morning.