I have a lennox cb26uh-036 gas unit that is heating and cooling the main floor of my home. It does something strange in the winter when we are using (obviously) the heating function. I'm pretty sure the BTU's are not sufficient for the amount of space it's trying to heat (roughly 1600 sq ft) as the unit constantly falls behind the set temperature. Here's the part i don't understand, as the unit is in heat mode it will eventually stop producing hot air for a certain amount of time and continue blowing cool air. After a little while, it will start producing hot air again. I can understand that a unit is too small to heat an area greater than it's capacity; i don't understand why it would stop producing hot air in the heating cycle. Any help would be greatly appreciated!