"Joseph Meehan" wrote in message

More a matter of no more than 30 minutes run time per hour. Less on a
hot day and maybe more on a cold day.

Right, and some have a number of "starts" per hour limit. If it runs 15
and is off 15, you have 4 starts per hour. If it runs 1 minute off, one on,
you have 30 starts and a lot of strain.