New Steam gas boiler runs for short cycles at a time Honeywell RTH6360D1002 5-2 Day Programmable -

Steamheatnewboiler

Dear all
After many years i finally purchased a new Dunkirk gas steam boiler 82EFF. I have a honeywell t3 thermostat with the smart response feature on isu 205 setting 12 for steam. The boiler comes on and off several times in the callback period sometimes like 7 times in an hour and a half. Short minutes bursts. On and off. Nevertheless, the temperatures are fine and the home feels comfortable.

Is this cycling on off normal? Will it mess up the boiler it took me so long to replace? The heat comes up fast, but since i want the temperature at 68 at 6 am it begins to run like at 5 am in short burst of time. I thought this was called short cycling, will this mess up my new boiler should i replace the thermostat? I have a Honeywell RTH6360D1002 5-2 Day Programmable Thermostat
with the Smart Response on. Thanks for your time.

Steamhead

Did you set your heating cycles per hour in the thermostat to 3 or less?

Jamie Hall

This may sound like an obvious question, but I've got to ask it... are you sure it's the thermostat turning off the boiler? You say you got seeting 205 at 12 -- how about 200? should be 3

Steamheatnewboiler

Hi ISU setting 200 is at 3. I do nor see a way to control the CPH directly. Thanks

Steamheatnewboiler

So as the season starts do i let the Honeywell thermostat smart function control my boiler with the so called Smart function or turn it off. My only concern has always been how many times the burners turn on and off in an hour. It runs for 11 minutes then 5, then, 3 no discernible pattern other than several on off in an hour. At least 7. Runs great though. But I need it to last. Love and respect the knowledge in here. Amazing.

Jamie Hall

I'll go back again to @Steamhead 's comment: did you set the thermostat in its programming options to 1 or 2 cycles per hour, if it calls for that, or "steam or gravity hot water" if that's the option? If not, it will do exactly what you are seeing, as they come with a default setting of 6 cycles per hour, which is correct for hot air but not for anything else.

bburd

Is the burner cycling on the thermostat… or the pressuretrol? Many if not most boilers are oversized for the radiation, and will cycle on high pressure during recovery from setback.

109A_5

Hello @Steamheatnewboiler,

Steamheatnewboiler said:

My only concern has always been how many times the burners turn on and off in an hour. It runs for 11 minutes then 5, then, 3 no discernible pattern other than several on off in an hour. At least 7. Runs great though. But I need it to last. Love and respect the knowledge in here. Amazing.

If the 11, 5, 3 is typical of a recovery from a setback there is a pattern. You are at the mercy of whatever algorithm Honeywell (and possibly others) are using with a thermostat to provide you with best comfort in their opinion (with the heating equipment settings you selected).

You may find the same (or very similar) Gas Valves are used with a Steam Boiler as with a Forced Air furnace unit, although the expected CPH (Cycles Per Hour) are different.

I don't see any provisions for setting Cycles Per Hour with that thermostat. If that criteria is even used it is probably embedded into the settings available. They are probably going for a less confusing user setup strategy. Settings as others have stated.


As an experiment I would try 205 - 9 just to see what it does.

Some folks do not recommend setbacks with Steam, some want to try to get some fuel savings, others want it cooler when sleeping and some prefer comfort and don't care about Gas Valve life. You have to define your priorities (you may already have) and use thermostat equipment (or settings) that suites your needs. You may sacrifice some fuel economy and / or comfort for less CPH of your Gas Valve. You may have to experiment a bit to find what you like and how to do it.

The relative position of the thermostat to the radiator that has the most influence on it may make a difference. Also the venting rate (one pipe system) of the radiator that has the most influence on the thermostat.