Some programmable stats (like my White-Rodgers) have a thing where they turn on the HP ahead of the time you set for the temperature change. That way they run the HP without using the heat strips. On mine it is called 'Selectable Energy Management Recovery'. It uses 15 minutes for each degree for heating recovery, so if the setback is 8* it will start two hours early. This time is self-adjusting and will be longer or shorter depending on how successful it was the previous day in hitting the desired temperature at the right time.

A setback t-stat saves energy while maintaining comfort better than non-setback. If for no other reason, it eleminates times you forget to adjust. Even inexpensive setbacks don't activate strips on start up,you must switch to "aux" heat unless heatpump has provision for switching over at predetermined outdoor temp.
If your hp doesn't switch over when temp reachs a certain point and it interests you to retro fit your hp,you can do it using a single pole double throw switch that makes/breaks at whatever temp your hp starts to struggle. You still must use a setback t-stat unless you continue to "nudge".

>Even inexpensive setbacks don't activate strips on start up,you must switch to "aux" heat unless heatpump has provision for switching over at predetermined outdoor temp.

This is not true. Most inexpensive setback stats DO immediately kick on the aux heat during setback. There is no manual activation of aux heat, the thermostat decides whether or not to use it. Maybe you're thinking of emergency heat which is a totally different ball of wax.

Setbacks are generally not a good idea on heat pumps. Even if you have a "smart" thermostat that holds off on the aux heat during recovery, you are only going to get away with that in milder weather. As it starts to get colder, the heat pump is only going to be able to maintain your set point, not recover on its own.

My advice for heat pumps is to only do setbacks for comfort purposes (cooler at night) and not to try and save energy (you won't). I would keep the setbacks small (just a couple degrees). That way, the heat pump may actually be able to recover on its own if you have a smart stat, and even if you don't, the aux heat won't need to be on long to recover.

"There is no manual activation of aux heat, the thermostat decides whether or not to use it. Maybe you're thinking of emergency heat which is a totally different ball of wax. "

I take exception to most of what you say but the above statment is simplest to discuss. I submit the source of energy comes from electric heat strips in the op's case,be it auxiliary or emergency. The only difference being wherther activated manualy or automaticly. If you believe all the research resulting in setback t-stats reccomended for energy savings is incorrect that's your right. It;s also your option to say so anywhere anytime. On the other hand it's cheesey nit picking at words and terms that are commonly used enterchangably.

>On the other hand it's cheesey nit picking at words and terms that are commonly used interchangeably.

OK, but what you said about thermostats not activating aux heat on their own was just plain incorrect. The backup heat can be activated manually with the emergency heat - OR the thermostat can activate it if it deems it necessary. The definition of "necessary" depends on the thermostat you buy. For cheapo ones, all it takes is a couple degrees between the set and actual temperatures. Higher end ones use more advanced algorithms to save more energy.

>If you believe all the research resulting in setback t-stats reccomended for energy savings is incorrect that's your right

I never said setbacks were always bad, I think they are beneficial for most of this country that has straight gas/electric heat with a single stage AC outside, especially given all the poorly insulated houses and oversized systems out there. But on HEAT PUMPS, yes I think setbacks do more harm then good. The fact is that heat pump capacity drops along with temperature, and there is nothing a fancy thermostat can do about that. Maybe you live in a climate that rarely gets under the 30s, in that case I can understand where you're coming from. But where I am, there is a good part of the year where temperatures are warm enough that heat pumps are still useful, but cold enough that they need the help of aux heat for recovery. The choices are,

A) Setback and use a cheap stat that kills my electric bill by using aux heat to recover

B) Setback and use a fancy stat that holds back on the aux heat, but consequently takes AGES to try and recover, and eventually has to call on the aux heat for help anyway

C) Don't setback

Which would you pick?

B for most of the time.

D) Smart recovery setback thermostat with a lock-out on the auxiliary so it doesn't trigger at all (unless the outdoor temp is below the lock-out temp, which is a different factor).

That worked for me when I was doing a 12+ hour weekday setback. No big deal if the target recovery temp is short by a couple degrees at the target recovery time. The system was blowing warm air, the house felt comfortable.

I guess you're all in warmer climates. Sorry, I was just speaking from personal experience, and I guess in NC it could be different. By all means set back your heat pump with a smart thermostat if it isn't too cold out. Where I am up north, for much of the winter there is no way a heat pump is going to recover from anything but the smallest setback with help from the aux heat. If you fired up the heat pump when you got home, it may not have even gotten to your setpoint by the time you went to bed and turned down the thermostat again. Yet if you had kept your hands off the thermostat, it would be holding a comfortable temperature with little to no aux heat use.

This post was edited by hvtech42 on Mon, Oct 13, 14 at 19:56

Thanks guys, you are trying to answer, and I gather there may be a variety of stats that use different protocols. Some might not be to my advantage and unfortunately it sounds like I might have to guess.

However it sounds like all of you may have missed one of my critical introductory points. I Have Two Heat Systems and an open floor plan. The lower unit is propane and I assume you all recall that hot air rises. Once we are moving, bedroom doors are open.

Sorry, you're right I did miss the part about the propane furnace. I would recommend just installing a manual switch for the aux heat that you can turn on and off as you please.