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Can constant circulation cause short cycling?

D107
D107 Member Posts: 1,849
glad to hear that. Unfortunately I've been unable to convince my mother to raise night t-stat setting above 60. (But 2107 night setting is 64, which should help a bit with recovery.) I guess that's her night comfort level; she might partly think she's saving money, but probably the opposite--raising that curve is certainly costing her a few percent.

About the basement, yes I guess turning the rads on and insulating would be better. Losing the heat from the supply piping--which mostly gets wasted up to basement ceiling must be less efficient than supplying the convectors.

Thanks,

David

Comments

  • D107
    D107 Member Posts: 1,849
    Drops supply water temp quicker?

    I was out at family house and noticed very frequent heating cycles on Buderus G-115/21/Riello w Logamatic 2107/oudoor reset. Outside temp about 38 degrees. 2107 settings standard for convectors. T-stat day-temp setting higher than 2107 setting, so Taco 007 defacto constant circulation.

    Cycles: 4:05 on at 110deg off 4:10 at 140; 4:22 on at 130, off 4:30 at 160:(DHW cycle?) On at 4:39 at 120. Delta T 30 degrees? I'm sure these readings are not the most accurate--temp gauge is small and not so easy to read but the point is the boiler was cycling on every 10-15 minutes or so for about 8-10 minutes and it wasn't that cold out. 4x an hour seems like a lot of cycling to me.

    Note that there is no insulation on basement supply piping for this 1" monoflow system. (there is also a 3/4" 2nd circuit baseboard system for porch extension that is always kept at 60 deg.) Basement rads are off. I thought perhaps the uninsulated, unheated basement temp of around 67 or 68 was sucking heat from supply piping, lowering boiler temp more quickly. Or I thought the roughly measured 30 degree Delta T indicatess the reasonably insulated house--except basement-- simply requires that amount of heat input frequency.

    I recall that the general advice is to have the T-stat in a central location where it is likely never to be satisfied, therefore giving you defacto constant circulation. I'd have to believe that constant circ dissipates heat to piping and emitters more rapidly than standard non-outdoor reset systems wastefully release it through the flue.

    Due to room temps taking a bit too long to come up to temp after night setback upon advice from Buderus I raised offset to 2 (raising lower end of curve) and day temp to 74--keeping room t-stat at 70--thus boosting curve at upper end (for when it's colder outside.) I haven't had a chance to re-check cycle times since then, but I suspect higher water temps may help the short-cycling, if it in fact what I've described is short-cycling.

    My concern here is boiler/burner wear and tear--and, to a lesser extent, fuel expense. I know we're doing much better than old boiler. A more recent rough estimate of usage given curve upgrade and colder outside temps is about 65 gallons over 13 days and 380 degree days. (2100sq ft house, 50K loss, 100K emitters).

    Thanks,

    David


  • that doesn't sound like short cycling, and personally I would not sacrifice a well set reset curve for setback.

    Raising temperature does not help cycling, it just lowers efficiency. Raising the differential would help with cycling, but again it doesn't sound like you have a problem. You may be bleeding heat to the basement and such though and so if you don't want it heated, insulate that piping.

    Some of the other guys around here will have more interested feedback I bet!
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