[Closed] oil boilers

Should fire when:
hot water timer is on and tank stat says go and circulating water temp says go
or
heating timer is on and room stat says go and circulating water temp says go

otherwise no

(that's how mine work anyway with indirect hot water)
how are you sure there is no demand ?

no demand - no CH on and no taps running - assumed the water heating was "on demand"

Is the boiler outside or in out-buildings?

If it is it may have a built in froststat which should be set to fire the boiler when the temperature reaches what its set at. It is likely that this would be around 5 degrees but may be higher.

Its also possible that there is a stand alone froststat not integrated within the boiler.

If you havent been there long have a a search, frostats can look like a normal room thermostat with a lower range of temperatures or can have a cover over the dial to prevent people altering it.

What is the boiler make and model? If its a combination boiler ( hot water on demand ) then its working correctly. With oil boilers, the heat transfer into the hot water is slow due to time it takes a oil boiler to reach full working temp. The boiler will keep a small amount of stored ho****er, so when you turn on the tap you don't have to wait 5 mins to get hot water. This store is always kept hot so the boiler will fire with no demand on it.

If its not a combi, then yes, check the frost stat.
Hope this helps.

What Chris said is correct - check those first.