"technics100" wrote in message
...


SNIP


The boiler does everything as you describe and will run from cold until
it get hot and then it seems to trip. It trips a transparent box which
lights amber, I just press the button in the middle of this box and the
light goes out, the boiler starts and runs until it trips again. trips
sooner when its hot

Thr transparent box will probably say Sartronic 830 or something similar on
it and this is the sequence control which operates the burner and monitors
the flame when a heat demand is present. You still haven't told me what make
the burner is but using a Sartronic suggests you may have an Inter-Oil
burner unit with a Danfoss oil pump (the black block thing with the oil pipe
going in). If you do then depending on the age it will probably have a
solenoid coil mounted on a shaft. One fairly common failure mode found of
late is for these coils to go open circuit when hot but remake when cooled
by an indeterminate amount taking anything from a couple of minutes to
several hours for the problem to occur. Its sheer indeterminate period often
makes it very difficult to pin down. Other makes of fuel pump are also used
so all I can reiterate is please give full details of your burner and oil
pump etc. BTW have you checked the oil filter yet and was there any coating
of sediment/muck on the element?


I was reading this forum and around the net and thought that the central
heating pump wasn't pumping the hot water away from the boiler quick
enough thus causing it to trip. I left the boiler on a very low temp
setting all day and it has been running fine for approx 14hrs. Is there
any way to check the pump, to make sure its pumping at the right speed.
its a Grundfos UPS15-50. Any suggestion is appreciated.

Not all boilers have an overheat trip and in general all the overheat trip
will do is remove all power from the boiler panel thus "usually" the power
on light and others are simply dead along with the boiler until the overheat
stat is manually reset. The lockout button has no connection with the
thermostat system. This does suggest howver that the burner will fire for
shorter run periods and whatever is causing the lockouts is not getting the
same energised periods and avoiding the thermal effects.