I have a lennox heatpump/blower unit and noticed yesterday that instead of cycling on and off it ran pretty much all day. The high yesterday was 96 and I had the tstat set at 76. When I got home last night at around 5:30 it was on and I don't think it shut off until about 10:30. Is this normal operation during this type of weather? The tstat was reading 76 the entire time so I don't know why it wouldn't cycle on and off a little more often. On the bright side the house is cool, I just don't want the compressor to blow.

Cooling to 20 degrees below the outside temp is a lot of work. It's not unusual at all that it would run all day when it's 96 degrees outside. Nothing to worry about.

A hint: turn the t-stat up from 76 to 77 and you'll still feel cool and it will run much less... probably significantly less.