Boiler Short Cycle

mel rowe

If you're getting heat to the first floor t'stat area so quickly that it shuts off before feeding the second floor, I'd also have a look at the venting of the main(s) and the rad valves as to how balanced the system is. Ideally, the mains should vent completely before the rads start to feed. Then the rad vents should be sized such that they all start to heat at about the same time, with the area around the stat being the coolest in the house. This would give you much more even heating. Changing the stat to keep the boiler operating longer to get to the second floor would also overheat the first floor and use more gas. So I'm not sure a different stat would solve your problem. If you have a look at the venting, and report back, I'm sure you can get lots of help. FWIW

Ken_52

Boiler short cycle-insufficient heat on 2nd fl

I have a two family house which has two stories and a partially finished basement. The boiler is a Dunkirk Plymouth Steam Series 11, 225 BTU gas powered system approximately eight years old and it runs very smooth and quiet. The radiators through the house are well pitched and fitted with Hoffman specialty 1A air vents steam 1/8 conn and the main steam lines in the basement have air vents at each end. The thermostat is a Honeywell Pro4000 5-2 programmable and it is located on the first floor living room and I might add that the radiator in this room is among the first to receive heat because it is close to the boiler. The pressuretrol is set a .5 PSI. The main problem is the boiler does not run long enough to send up sufficient steam to the second floor radiators on a consistent basis once it starts to cycle at any set temperature. For example if the setting from 10pm to 5am is 72 degrees and the setting from 5am to 10am is 74 degrees the boiler will cycle and run through the night for 2 ½ to 3 minutes each time to achieve the set temperature and this is not a long enough time to send enough steam to the second floor radiators. However @ 5am when it has to make up a 2 degree difference it will run for approximately 20 to 25 minutes (depending on the external temperature) thus producing more than enough steam to make the second floor radiators very hot. As you probably guessed once this set temperature is attained then it cycles for the short 2 ½ to 3 minutes again and the second floor is not heated properly. The (self adjusting) air vent size goes up to six and I recently increased the size on the larger radiators on the second floor to size six while the radiators on the first floor are mostly set at size one except for the living room (location of the thermostat) which is set at one half of one. I reside on the first floor and would very much like to keep the thermostat on that floor. I was informed by Honeywell that all of their digital thermostats are designed to react within plus or minus one degree. My goal is to have the boiler cycle less frequently and run for approximately 8-15 minutes each time to send sufficient heat to the second floor on a consistent basis. I would appreciate if you could tell me what the problem is and explain how I could solve it. Thanks in advance for your kind and prompt response.

steve_29

Check to see if you have a plugged pigtail.

JohnG_3

Also Check the T-Stat

Some of the Honeywell T-Stats have configuration options for the type of heat you have - hot air, hot water, steam, etc. Furthermore, the T-Stats that are configurable are usually defaulted to hot air. I have an older Honeywell T-Stat that was running in hot air configuration for 10 years for my steam system. I finally fixed it and my boiler now stays on longer. I probably also have a clogged pigtail and non-functioning Pressuretrol but that is another story.