Most of the time it is on high limit on a call for heat. I have 7 zones hooked to it so it is rare not to have 1 calling. I set high limit 185 and low 160 with the differential 10 on both. i am a little worried about putting the high up to 200 as I have pex in the system. on the rare ocassion that there is not a call it is usually 170-175. Today it only used 160lbs for 24 hours.