Question:
I have one of those Honeywell programmable thermostats with multiple set points for different times of day. It is running my single zone (one Taco 007, no zone valves, flow valves at radiators), two-pipe hot water system. The boiler is a two-year-old Weil-McLain GV5. I have friends with forced air that swing their room temps all over the place. They feel that they are saving money. My question is, does that make good sense with a different animal like a boiler? Does it have a heating cost benefit or is it hard on the boiler? Is it better with my single zone to maintain one even temp? If you do believe in swinging the temps, do you range them very much? (My system drops to 66 degrees F at night and while I am at work and then 70 degrees when I am home.) Dan M.
Replies:
If you have one of our Chronotherm 4 programmables, T8600 family, you have “Adaptive Intelligent Recovery.” To make a long story short, the stat starts the recovery period from setback temp so that the set point is reached at the beginning of the “wake” or “return” period.
A reset system works very well for hydronic heat, as others on this site have termed it, “cruise control for your house.” Basically, the colder the air gets outside, the warmer the water gets in your system. It’s all handled automatically. We make several controls that do this, so do others, and some may require some piping modifications. Go to http://hbctechlit.honeywell.com; from most standard hydronic installations, either the AQ475 or the AQ675 works best. BillW@Honeywell
Comfort vs. efficiencies — a teeter-totter trade off. You can’t have it both ways. First and foremost, insulation is the most efficient way to stay warm. Second, replacing lost heat is always costly. Third, comfort means that you have to replace heat. The swing you refer to is a savings only as you can accept the heat loss your building has. You’ll have to look at your fuel bills and access your savings to your comfort. Comparing hot air to hot water heat is just not possible. The whole comparison is off by a floor-to-ceiling temperature difference and a draft factor. Bigugh
Two things you should keep in mind: building mass and thermal expansion.
If your house is tight and has high mass, it won’t significantly cool down during the setback phase and it will take a long time (and use a lot of energy) to get back up to temperature. The higher the mass, the less the energy savings benefit of using a setback thermostat.
With thermal expansion you need to keep in mind the effect of the temperature swings on the interior of your house. The wider the swings the more things (like your hardwood floors) within your house will be expanding and contracting each heating cycle. Uni R.
