A Cycle rate is the maximum number of times a system will run, in an hour, when using 50% of its capacity to maintain a given temperature. For a high efficiency (90%+) gas or oil forced air systems would have a recommended cycle rate of 3. This means the heating system will cycle a maximum of 3 times in an hour. If it is really cold outside the heating system will be on longer and cycle less, if it is mild outside the heating system will run less (be off longer) and again cycle less. Again, the actual on and off time of the heating system will vary as the load on the heating system varies.