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Thread: do I have a short cycle problem?

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  1. #1

    Default do I have a short cycle problem?

    Sometimes my burner runs for only 2 minutes..this seems to be a pretty short run time, to me it does not seem efficient and it seems that I would have more expansion/contraction cycles on the boiler..do I have a short cycle problem?

    Here are the particulars..

    Oil/hot water system installed summer of 2007
    Peerless hot water boiler WBV-03
    Carlin EZ-1HP Burner
    Honeywell Aquastat L8124A
    Hi 180
    Lo 160
    Diff 10

    I have 3 heat zones and 1 domestic hot water zone..indirect tank..(Amtrol)

    I never noticed the short cycle with my old boiler/burner. I started noticing it this winter (CT). Called my oil company and they came out, at the time they felt Aquastat was bad..you could hear it's relay click on-off when you pressed on the Aquastat housing..(they felt it had an intermittent open).

    Still have this 2 minute cycle issue. I can see that the boiler water temp will rise by 10 degress (from 150 to 160) in 2 minutes.

    This short cycle scenario just happened...
    I heard the burner fire..went downstairs to check..one heat zone's pipe were hot...others and hot water zone not hot. Burner runs nearly 2 minutes shuts off..boiler temp about 170 degrees. Almost 10 minutes later burner fires again...runs about 1 minute. Same Zone as earlier has hot pipes..circ pump is running and boiler temp is about 170 degrees.

    Does that cycle scenario seem to be normal?

    I've been trying to understand the relationship of the water tank t-stat to burner operation. On my boiler aquastat I think the ZR terminal is connected to the water tank t-stat.
    Is this a correct sumation of the realtionship:
    When the water t-stat calls for heat..the tank circ runs and the burner fires (regardless of boiler temp, assuming the boiler temp is not at the high set temp)..is that correct? This happens on the ZR term..it enables a make on the oiler burner circuit?

    On a related question..while the burner fires should the circ pumps for the heat zones shut off?

    Thanks for the help

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    That does seem like a short cycle. Can't help in that regard, but wonder if the high/low settings are proper.

    If a circulator isn't running while the burner is firing, the water in the heat exchanger could boil creating all sorts of problems.

    An indirect WH is usually set up as a priority zone...i.e., it runs and shuts off all other heating zones temporarily until the WH has reached temp.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014


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