boiler in loft and frost stat?

We have a new boiler was installed in the loft last month, it has a frost stat. we were told that it heat the water when the temp in the loft is below a target temp say 3c. there isn't a radiator in the loft and it will get very cold during the winter, does that mean the boiler will be running cntinutesly in cold days, that's like 3 months in a year. what will make it stop? does that mean the loft is not a place for a boiler at all?

I feel quite angry because the plumber who did our new boiler didn't say this, we would have had it put in a bedroom instead