what are resonable set back points for geo?


i am wondering how many degrees is to much. on my non-geo system in winter i do a large set back 10 deg. (68 down to 58)

What you are asking is more of a generic question that pertains to the mass of your interior and the output of your heating system. High mass, low output systems should not do very much setback. Low mass systems can do much more.

I do not use setbacks that exceed 2f. There is not much chance of engaging aux heat when recovering with such a low setback (and eliminating possible savings), except on the coldest days. Setbacks can be eliminated on the coldest days. We do it for comfort. If your system is designed, installed, and functioning correctly, savings probably won't be that great from setting back. If setting back more than 2f, and if aux heat is locked out, recovery times may be longer than you desire.

I have my Main floor set at 70F and the thermostat set to 3F. IE comes on when 67F. I have 1300 sq feet tile on slab in floor system on the main floor. Takes approx 2 hrs to bring to 70F. We are very comfortable and the floor radiates the heat for several hrs after. I guess I could go w 2F. i rather the system run for longer less frequently. Whatever is comfortable for you I guess. I do not set back more at night or use a programmable thermostat. If I go away for a couple of days or more, I will drop back to 65f (cut in at 62F) Does not make sense with our infloor system and recovery time. I do not have the aux heat set based on the temp in the house. It is based on my home's balance point. It appears that is around 10F and then the buffer tank elements kick in

So many variables....ie in MI one of the electric providers discounts based on time of use so electricity is cheaper at night making set backs a horrible idea. If you were to dial down when you leave for work (when electricity costs more) it can be advantageous as long as auxiliary is not employed.
Joe

Cheap power at night might make it pay to raise stat setpoint during the night and let the house store some heat.

In the 90s I had a townhouse near Philly with oil heat and central air. I moved the central air to the interruptible meter whose power cost less than half the regular meter. No AC from 1pm to 5 pm on weekdays, but on hot days I programmed the thermostat to cool the house to 68 during late morning, and that worked well enough to keep the place reasonably comfortable.

Posted By blackflag on 15 Apr 2010 10:43 AM
what are resonable set back points for geo?


i am wondering how many degrees is to much. on my non-geo system in winter i do a large set back 10 deg. (68 down to 58)

There are two main issues you need to consider when using setback for Geo-systems.  A. Recovery times are somewhat longer, so if you set your setback is too big, recovery times will be longer (assuming your Aux heat is disabled) B. If your AUX/Emergency heat is not disabled, when the difference between the current temperature and the setback temperature is too large, the AUX heat will kick on and more than erase any saving your setback would have saved you. Generally large setback for Geo systems do not make sense.