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Is this short cycling?

Tommy does your system have main vents on it ,and are your mains insulated also is your heat anticapator on your thermostat set correctly to the amp draw of your gas valve or to what the manafucture has suggested it be set to also make sure that your pressuretrol is set correctly make sure that the cut in screw is not total slack and that there is some spring tension and the differental set to 1 peace and good luck clammy


  • Tommy_5
    Tommy_5 Member Posts: 1
    Short cycling or am I expecting too much?

    I have a 1 pipe gas steam boiler which I believe is matched correctly to the EDR of the rads and pipes.

    Everything runs fine on initial start up,, boiler runs continuosly, pipes heat up, all the rads get hot with no hissing or spitting vents. Everything is great this first initial cycle.

    Then it shuts off on pressure for a few minutes (2 to 3) then restarts for a few then off again. Over and over until the thermostat is satisfied.

    My p-trol cuts out at 1.5 and cuts in at .5 (going on memory here but this is close enough).

    Am I expecting too much to expect the boiler to run continuosly without shutting off just on pressure? Should the cycles be longer then 2 to 3 mins? My system is quiet with no water hammer or whistling vents.

    The only noise I get is when the boiler shuts down when the t-stat is satisifed..Some of the air vents whistle!

    Im guessing its the pressure drop and resulting rush of air back into the steam pipes via the air vents. Several vents whistle at once and its noticable for the 1 to 2 minutes that it takes for the pipes to fill back up with air.

    IS this a sign of something wrong??

  • Ken_40
    Ken_40 Member Posts: 1,320
    Sounds as if you may have a

    vent problem.

    What brand vents? If the cheapies, the vent holes are drilled and sometimes a slight burr remains. If you GENTLY use a countersink to bevel the burred orifice, you may reduce the "whistle."

    As Clammy mentioned, the main vent may be undersized, forcing the rad vents to overcome the undersized main vent's inability to gently allow the system's refilling with air on shut-down/vacuum...

    Your pressuretrol settings are perfect! Nice job on that one. The heat anticipator on your stat may be adjustable? If so, make the on and off cycle longer. The rule of thumb I prefer is to make the cycles as long as possible - without having any sense of "hot or cool discomfort."

    Sounds like your problem is not stat related, but just the pressuretrol cycling. That being the case, you are probably best off leaving the stat anticipator as is.

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