the lockout halstead best 60 boiler overheat lockout ?

Halstead Best has Two Lockout conditions, Overheat, and Combustion lock out, if overheat lock out, has the circulating pump been wired to the boiler so that the heat disipation function can work? otherwise you could be looking a a faulty Thermistor or overheat stat.

If Combustion Lockout, Bests are nororious for Gas control Valve and Combustion Control box problems

You should get the Boiler Checked by a RGI
www.gassaferegister.co.uk will assist you to find an Engineer near you

www.elanar.co.uk
August 2009

Too much soot in the boiler top and first part of the flue, I suspect. Too much soot gives an alarming increase in flue temperature.

John
August 2009