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(2) Vitodens 200 B2HB with vitotronic 300 control

platestealer
platestealer Member Posts: 4
in THE MAIN WALL
Can anyone explain how/when the vitodens 200 fire on with the above set up? It was commissioned/start up by the sales rep techs, but hasn't needed to really fire on until a few days ago when it got colder. Yesterday, the loop temperature set point was 75 F and the actual loop temp was only 65 and didn't fire on (it later warmed up in the day and didn't need to go on (after a few hours)).

A few days ago it got even colder, but eventually did fire on when the loop temperature hit ~60 F.

I know Viessmann's have quite the controls, but I would like it to fire before the loop temp gets that far below the set point.

I know about the integral start threshold, but I adjusted that lower but yesterday when the loop temp hit 70, it didn't fire

Any light shed on the subject would be appreciated. I know once its on, it will modulate, but I really wish it would turn on sooner. The outdoor reset curve is pretty flat as it serves a water-source heat pump loop so the loop temperature stays pretty low during the heating season.

Comments

  • platestealer
    platestealer Member Posts: 4
    I did a little digging and on page 55 under the Cascade control of the Vitotronic 300 installation/service manual it says

    "Starting criterion:
    An output statement causes the boilers to be started
    (coding “3d:1” in the “Cascade” group)"

    My question now is what is an output statement. Looking under coding 3d does not give an clarification.

    I may just give tech support a call if no one has any answers.

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