Lochinvar Boiler is Not Throttling Back Like Usual

Discussion in 'Boiler Forum' started by dwassner, Dec 8, 2020.

  1. dwassner

    dwassner Member

    Jan 31, 2012
    Finger Lakes, NY
    I have had the boiler set up for a few seasons now with the current outdoor reset, differential, and offset.

    Tonight, I noticed that the unit was cycling on and off several times within 30 minutes.

    The current setpoint for the given outdoor temp is 131 f. While the boiler is off (and the system pump is running since both first floor zones are calling for heat) the system water temp drops its 20 deg differential, the boiler then fires up and throttles up to 100%, and only throttles back down to about 80% and by that time the system temp is already at 146 deg (the setpoint + the offset) and the boiler then reads 'setpoint met' and shuts off.

    WHAT IS DIFFERENT is that the outlet temp is significantly higher than usual (~160 deg) given the 131 deg setpoint when the setpoint is met. USUALLY the boiler would begin throttling back well before this high system temp was reached, and the boiler would continue to hum along at 20-30% chasing and never fulfilling the tstat.

    It is almost like the boiler doesn't realize it needs to begin throttling back sooner than it is...

    FWIW - the house has plenty of heat, the indirect tank appears to be functioning fine as far as it's setpoints and whatnot...

    Any thoughts?

    Last edited: Dec 8, 2020
  2. fitter30

    fitter30 Well-Known Member

    Feb 2, 2020
    Retired service tech
    Peace valley missouri
    Model of boiler
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