design temp and setbacks

neilc

suppose you nail a heat load/gain calc, size system to a teee, now work in a setback thermostat or control sys, picture design temp day, does system recover? is there room in the calcs for setback? should the setback be disabled for the once in a while extreme?
who see desing temp days anyway?
me thinks to much

Al Letellier

design temp

I would think that if you hit your "calcs" on the head, the system would recover on a design day, but......we have a system with 2 boilers and a Tekmar staging control that doesn't recover....because the customer insisted on set back thermostats. As hard as I tried, I couldn't convince them that outdoor reset would save them way more than setback. But it's a large church group and they have too many experts on site....the building does not recover on a mild day because they set it back too far. We installed Honeywell 7300 stats, set occupied/unoccupied at 70 and locked the keyboard, but someone found out how to fiddle with them, and the rest is history. I now charge them every time I go back to reset the stats.......sometimes you can try to save too much

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Boilerpro_2

Are you mixing outdoor reset and setbacks?

Not a good idea unless you can boost water temps to come out of setback. I do churches all the time with both, they typically see thier fuel usage drop about 40%. BTW recommend setback temp for churches is 45F, since must spaces are only used a few hours a week and to prtect organs, furnishings etc from low humidity. Maintaining a building at 45F instead of 70F in a 6000 DD climate cuts the length of the heating season in half.

Boilerpro