I just moved into a new home with 2 Janitrol heat pumps. Both heat pumps seem to go into defrost cycle frequently (about every 2 hours) Is this normal? The outside air temperatures at night have been in the 20's and 30's.

Defrost frequency will vary with system usage and outdoor temperature. The trial interval is usually adjustable via a jumper on the defrost control. Every two hours does seem a little frequent.