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Definition of boiler short cycling????

Okay, I see this question asked a lot, and I've never seen a really good answer. At what point is a boiler short cycling?

My Biasi's burner is cycling at about five minutes on, five minutes off on a boiler demand. This is being determined by the Tekmar 260 calculated differential (it is not hitting the aquastat hi-limit). The boiler is piped P/S with a TV valve on the return. The current outdoor temp. is well above the design temp, so I surmise some cycling is normal after the boiler has hot water flowing in the radiation and back to the return since the boiler is esentially oversized most days of the year. So, is what I'm seeing excessive, or to be expected? Should I play with the Tekmar's differential setting to reduce the cycle times--or does that defeat the smarts behind the Tekmar's programming?



  • hot_rod
    hot_rod Member Posts: 22,157
    a survey was done by PM Engineer

    mag a few years on boiler short cycles. The largest percentage agreeded a 10 minute burner on cycle was minimun. But this may have been for cast iron and non condensing equipment.

    Pete, formerly with MZ told me that the MZ was designed for many years of short on/off cycles. Just the sound of it cycling drove me nuts, regardless of the fact all the components were engineered to handle it.

    I'm waiting for the day cycling disappers completely. The heat source fires at 70f outdoor and modulates from IK to whatever without any cycling :)

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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