Honeywell tstat \"cycles/hr\" and low-mass boilers

Plumbob

We have a Munchkin with Vision I reset and P/S piping. It is connected to 2 Honeywell electronic thermostats, one for each zone. (These were pre-existing thermostats, we are not using the setback features.) The thermostats have no anticipation, but they have cycles/hr settings: 6 recommended for forced air, 3 for hot water or condensing forced air, 1 for steam.

First, hydronics systems generally need longer run times, but do low-mass boilers mind being turned on and off 6 times per hour?

Second question: I don't know what cycles/hr means when there is outdoor reset. I would expect that if the curve is set pretty well, there should be calls for heat lasting several hours. Is this thermostat going to cycle the boiler on and off 3 times an hour anyway (pretty stupid if true), and if not true, what does the cycles/hr setting mean during actual use?

Third question: Totaline manuals (although not Honeywell manuals) say that if the number of cycles per hour is increased, the temperature control becomes more precise. If I have outdoor reset and very long-lasting calls for heat, can I choose the 6 setting instead of the 3 setting? Will this give me twice as many on/off cycles, but still not all that many (say, one every 2 hours instead of one every 4 hours), but I'll get more precise indoor temperature control?

BillW@honeywell

You can reconfigure them...

We recommend the 3 cycles/ hour setting for a starting point for systems like yours. Just go into the "Installer Setup" mode, and change the factory default setting of 6 to 3. If you don't have an owners manual, go to http://hbctechlit.honeywell.com and type in the number of the thermostat you have (T8600, T8602 etc.) an you will get the complete installer setup instructions. The owner's manual is there as well, just click & print it out. Your system only would cycle 3 time/ hour when it was at or below whatever design temperature for your area is. In normal operation, it may only cycle one or twice in several hours, based on the load. With reset, you may want to try 1 cycle per hour, if that's too long, go back to 3.

Plumbob

thanks, more questions

Many thanks for the quick reply! I know how to change the cycles/hr. I don't understand it, though. You say it will cycle 3 times/hr only if we are at or below the design temperature, I assume you mean the outdoor design temperature, how does the thermostat know the design temperature for my area, and how does it work to achieve 3 cycles/hr when we reach the design temperature? Certainly the outdoor temperature affects how fast the house cools down when the heat is off, but many other factors (insulation, temperature of water filling the radiators) also affect it.

Also, why would I want to set it to 1 cycle/hr? What does that do, given that you are saying that cycles/hr doesn't actually indicate the number of cycles/hr? Will it widen the temperature swing? I want to reduce the swing.

Thanks again,