[kdean1]

Nothing wrong w/ 55*F. Upon start up of heat in the morning(wake), the major thing that the 'full' heat has to heat is just the air temp. It can take a few hours before the warm air heats up the couch,floor.walls,kitchen/dining table,rugs,etc..And the t'stat cycled the furnace on/off several times. And typically the HO is already off to work (leave) as all of the items in the house are still warming up. Then the daytime temp can be set, no one home.. Then before/as you go home from work (return/arrive) the t'stat warms up the house as you head home. Again, the air warms up quickly and the other stuff warms up slowly. Then the 'nite/sleep' setback happens when the 'sleep' mode kicks in.

Known as Mean Radiant Temperature of the mass of the materials in the house. When the house is absorbing heat from your body, you feel cold. A stable house temperature is comfortable.

 

[kdean1]

Something else to consider is the size of the equipment. If the furnace is accurately sized for design temperature, it only has enough capacity to maintain a setting when at design temperature. Oversized equipment would have surplus capacity to recover from a setback. Conservatively sized equipment would run at full capacity and only hold the temperature until the ODT rose.
This is rare for furnaces because availability of a 30k BTU (for example) is rare, so the furnace is often somewhat oversized. But it can be a problem with a heat pump unless some supplemental heat is provided.