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Short Cycling - How short is too short?

Boilerpro_3 Member Posts: 1,231
Steam is usually best at about 1 cycle per hour, maybe two. However, an oversized boiler and/ or and oversized system will require more cycles per hour to keep an even temp.

Generally 3 is too many and can give poor steam distribuation in addition to higher gas bills.

I would lenghten the cycle time as much as possible until you begin to get the see saw effect on temperature and then back it off some to even out the temperature.



  • Robert O'Connor_3
    Robert O'Connor_3 Member Posts: 272
    Short Cycling - How short is too short?

    I live in Philadelphia, and I have a 100 year old 2-pipe gravity return gas fired-vapor steam system, with a 1983 175 BTU Weil-McLain boiler. I am trouble-shooting my high fuel consumption (10 ccf/day from 11/20 to 12/1, 15 ccf yesterday).

    During a typical mid-evening hour, my boiler ran for 20 minutes, but not all at once. It was on for 6 minutes, then off for 13, on for 7 minutes then off for 20, on for another 7, and off again.

    Is this short-cycling? My boiler will run for much longer (45 min) in the morning, when it is heating up for the day. I read in "the lost art of steam heat" that a desirable burn time was 20 min. Is my burner wasting fuel with the 6 and 7 minute burn times?

    Thank you to everyone in advance. I've learned quite a bit here on the Wall already.

  • Fred Harwood
    Fred Harwood Member Posts: 261

    That's not bad. Plus that's a 20-minute cycle, for about three cycles an hour, which should keep even heat in the house.

    What kind of thermostat? And does the heating cycle cause any overshoot in temperture?
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