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Buderus Logamatic not reaching reference temperature

pservais
pservais Member Posts: 5
in Thermostats and Controls
We're freezing here in MA, temp outside is 9F. I read a lot last night about Logamatic settings on this forum and found some very knowledgeable people who I hope can help me. We've had problems in the past where the system doesn't keep up on colder days (sub 20 degrees). This time, with all settings the same, the house has dropped to 55F. We have three zones and two Trane air handlers. The boiler is short cycling between 140-154(ish) while the air handlers are running full time blowing barely warmed air. I tried moving the reference temperature up to 170 with offset 0. No change in the cycle. Any suggestions?

Comments

  • Ironman
    Ironman Member Posts: 7,537
    It it sounds like you’ve got a circulation problem. Are the pipes going in and out of the AHU hot when it’s running?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • pservais
    pservais Member Posts: 5
    More information, each zone has a programmable thermostat but we leave them statically at 68F.
  • pservais
    pservais Member Posts: 5
    Ironman: Great question. The pipes are heating up to both zones. Yesterday, one return line was cold until I realized I had shut off the zone during troubleshooting. :( We had a tech out yesterday and he said that our boiler temp wasn't high enough based on the volume of air being pushed over the coils. Hence, my attempts to increase boiler temps.
  • Ironman
    Ironman Member Posts: 7,537
    But is the RETURN line from the AHU hot when it's running?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • pservais
    pservais Member Posts: 5
    Yes, the returns from both AHUs are hot when it's running.
  • Ironman
    Ironman Member Posts: 7,537
    Most hydronic coils in AHUs are over-sized and will provide plenty of heat even with 140* supply water temp.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,537
    Turn the 2107 switch to "manual" and set the temperature dial to 180* and see what happens.
    CAUTION: this will cause the water temp in the indirect to reach 180* also and scalding is at risk!
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • pservais
    pservais Member Posts: 5
    To switch to manual, I set the burner control switch to manual and pushed the daytime only button (auto led is off). The aquastat is set to 180+. The boiler stills cycles off at 168F. I understand the risk of scalding, everyone's been apprised but the DHW hasn't exceeded 130F throughout.
  • Big Ed_4
    Big Ed_4 Member Posts: 3,004
    The problem with switching to manual and setting to 180 , the indirect pump will constantly run Bulding up the hot water temperature as well. .....

    Turn the knob to get the outdoor temperature reading , see if it's reading 9f as well .... They go ... If not replace the outdoor sensor . In the mean time go manual but shut the supply valve from the boiler to the indirect ..

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