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Boiler Not Getting Up To Temp

scoobybriscoobybri Posts: 5Member
I have a Laars Mini-Therm boiler. The outdoor temp just dropped to around 10F for the first time since we moved into the house. The boiler cannot keep up with the cold so I looked at the unit and noticed that the boiler is shutting off when the water temp gets around 150F. From that I have been reading, the temp should be around 180F before the boiler shut off. I did some research and found the max temp dial in the unit and bumped it up to 190F. This made no difference. It still shut off at 150F. The boiler comes on at about 130F like it says it should in the manual but I don't see any way to change the temp of where it shuts off normally (the dial setting is for the emergency temp shutoff.) FYI...Water pressure is about ~25 PSI at 150F.


  • AbracadabraAbracadabra Posts: 1,948Member
    When was boiler last serviced? Has someone cleaned the heat exchanger?
  • scoobybriscoobybri Posts: 5Member
    More info...The house was a foreclosure and all of the copper was stolen before we moved in. The bank had a plumber put all new piping in the house and rebuild the heating system so I believe that everything has been replaced/cleaned/etc. The question I have is why would a dirty heat exchanger cause the boiler to shut off at 150F instead of 180F? I realize that a dirty exchanger would stop the boiler from transferring heat to the water but I would think that that situation would just cause the unit to run continuously because it could never get the water to the shutoff temp, not shut off when it gets to a temp below what it should. I'm not being argumentative as I am a boiler novice. Please teach me something I don't know.

    Thanks for the quick reply, Abracadabra.
  • scoobybriscoobybri Posts: 5Member
    That was my first though when I saw the outdoor reset sensor mentioned in the current manual but I don't think that my unit has that feature. My unit is at least 10 years old and I found the manual that matches my unit in the "discontinued" section on the Laars site. It does not have a reset sensor listed. Here is the manual that matches my unit.

  • scoobybriscoobybri Posts: 5Member
  • scoobybriscoobybri Posts: 5Member
    Thanks for all your replies. I got it! There are 2 high limit dials in the system. One is the emergency cut off (center of panel) and the normal running max temp dial is on the far left. I had set the emergency to 190F but the normal one was set for 150F. Bumped it up to 180F and voila, I now have 180F water in my pipes.
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