Our old Thorn ODY-3 oil boiler has been playing up in the recent cold
weather. On a couple of the coldest mornings we have woken to a cold
house and found the boiler locked out. After 2 or 3 attempts it will
reset and run fine all day. I have set the programmable room stat so it
has been working all night and then it is fine in the morning so it only
seems to happen when it has had a long idle period and a chance to cool
right down. The oil in the Tiger Loop and the filter looks clear and
clean and I don't think it has been cold enough for the oil to start
waxing. This is only our second winter in the house but last year it was
fine even though there were some much colder nights. The only change to
the boiler over the year was a new pump fitted last spring when it was
also set up with a gas analyzer by the engineer. Any ideas what the
problem may be?

Cheers
Tom