Potterton Suprima 30-80

Boiler intermittently (every few days) locks out on what I assume is
overheat. Unfortunately the unit is some distance away at the flat of an
elderly (geriatric) relative so the symptoms leading up to the lock-out
are unknown.

Before calling in a service engineer I would like to be better informed;
hopefully to avoid a series of call-outs.

Is there anything I should be particularly looking at?

System pressure looks OK, by-pass is open, the slide switch on the
controller has lost the *detents* and I don't know what geriatric
fingers have been doing in between failures.

Pressing reset invariably gets the boiler going for a few more days.

regards
--
Tim Lamb