Hi! My mother has a heat pump that was installed in 1989 and still heats and cools great, but it goes into defrosting mode several times per day, even when the outside temperature is around 40 degrees Fahrenheit. When it does, the system switches over to the oil burner for several minutes.

She called the guy who installed a new fossil fuel kit last year, and he said that was because the system was low on refrigerant and added 2 pounds of R-22. Since he did, it seems a bit better, but it seems to me that it defrosts a lot more than it used to (with the old fossil fuel kit). Last weekend I was there watching TV for about 4 hours and the oil furnace kicked in about every 45 minutes for 4-6 minutes each time. The temperature outside was just below freezing. Can you please tell me if this is normal? Is this a sign that the heat pump is on its last legs? The heat pump is a 2-ton ICG, if that matters. Thanks.