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Cold firing question

gdowie Member Posts: 17
I've got a Buderus G115WS/3 and I've been transitioning to heating with mini-splits. Running the boiler less and less. I find that if the boiler is warm it fires up and runs nicely. Sometimes, if the boiler is cold, it tries to fire a few times before it "catches" and keeps running. My question is this:

I would like to only run the boiler when my ASHPs are struggling to keep up (below -10°F outside), and let it shut down during the winter when ambient is warmer than this.

Can I tune the boiler to start from cold better? Is there risk in letting the boiler shut down and cool completely to ~50°F frequently due to the bigger thermal cycles or more time at low temp when condensation in the flue may be taking place?

Thanks for your consideration.


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,378
    I don't think it's a tuning problem. Might be a slight vacuum leak in the oil line and/or may be a draft issue. Longer pre-purge may help, as well as properly checking to make sure there are no air or vacuum leaks in the oil line.
    No problem at all letting that boiler go cold.
    HVACNUT Member Posts: 5,478
    I could be a tuning problem if there's too much excess air. Do you have combustion numbers? What burner?

    Also, on below freezing windy days, it doesn't take much to freeze a heat pipe that's just sitting there doing nothing, unless there's antifreeze.