Cycles per hour

TeeDog

I have a 5 yr old Honeywell Programmable Tstat that has a cycles per hour setting.



The manual leads me to believe that I should have it set at 4 for my gas furnace, however I notice that it cycles several times when its set to rise from 64 to 68 first thing in the morning, and it cycles a few times an hour throughout the day.



I guessing that  lowering the cph should make the 80% furnace use less fuel with the temp differences being more noticeable.



Can I lower the cph until the room fluctuations are a problem, then bump it up one, or am I way off in my thinking?



Or  can you recommend an alternative stat that does not have cph , but adjust-ability for temp swing instead?



Thanks.

Jim Davis_3

cph

Less cycles per hour doesn't save any money if you are trying to maintain the same temperature.  Sure will make you colder. 

Today, the mentality is consumers really don't want the temperature in their house to be what they set their thermostat for.  So we have controls and equipment that avoids satisfying the setting.

TeeDog

but why?

Why would my tstat cycle during a scheduled rise of 4 degrees?  Why not stay on until the tstat is satisfied?



I thought that forcing the furnace to come up to operating temp 3 or 4 times vs once would be more costly.

icesailor

Cycling:

It's my understanding, and I probably misinterpreted it. But, the "cycles per hour" have to do with how many times per hour that the thermostat "checks" itself to see if it needs to come on. If you have high mass emitters like cast iron radiators, they usually are set to one cycpe per hour because they release heat for such a long time. High output, low emitting heaters like copper baseboard heat up quickly and cool down quickly. So the thermostat needs to "check" more often.

I have setback thermostats. I hear the one near me click all the time, but it is always comfortable and the swing is never more than two degrees. If the setback starts, it just doesn't come on.

TeeDog

Thats my understanding of ow it works too.

I guess I dont see why this is advantageous over an anticipator or swing setting.



Adjust the swing temp for comfort and let it come on when it needs to.



Now I have to live with a preset swing temp and tell the Tstat how many times an hour it can check it.



If the swing temp is tight, as mine appears to be, then it will come on every time it checks...even if it just shut off a minute before.

icesailor

Cycling:

That's not my experience with mine.

TeeDog

Update

I have been running the stat with the CPH set at 2...its lowest setting.



I've been checking with my wife who is much  more sensitive to cold than I am, and she says shes been quite comfortable.



I was a propane tech on RVs for 24 yrs and was always told, and it sure makes sense, that the least efficient part of the cycle is start up.  Until the combustion chamber came up to a particular temp, the flame was not burning at peak efficiency.



 As well, the heat exchanger had to rise to a set temp to activate the fan switch.



The fewer number of times you have this situation over a day, the less fuel you were burning. 



When my CPH was set at the recommended 4 times and hour, it would come on, 4 times and hour and the burner would run for 8 mins/cycle, or 32mins/ hour.



I set it to 3 CPH and didnt notice and temp swing, and the burner ran  for 10mins/ cycle, or 30 mins per hour.



I have had it set to 2 CPH and we're still comfortable, the burner runs for 12-13 mins per cycle, 24-26 mins/ hour and only 2 of the less efficient warn up cycles.



These changes were made during a very cold snap here in northern Colorado,  and now that its been warmer., the cycles are shorter still. 



My furnace has just cycled while I'm typing this...9 mins.



How can I not be saving money?