pre-heat??

boiler fires up at 4:00 am (not programmed time)
runs for 10 mins then switches off for 5 mins
and runs again 10 mins. cycle continues.
have checked programmer all seems fine.
I am wondering if this boiler uses a pre heat?
or whether it is the frost stat telling boiler to run?
boiler is located in garage? ambient temp around 20 deg.
boiler make: ideal isar 24

ljk75
December 2011