Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Burning at orfice

kevsul1 Member Posts: 23
I just installed a two stage gas furnace (switched to propane) in my attic took a look at it tonight and when it lights two of the three orfices are lit going into the Venturi never seen this pressures are good on high and low fire and the inlet changed to new orfices I had still the same thing the only thing is I don’t have my fresh air vent ran but I don’t think this would be the cause any thoughts


  • DZoro
    DZoro Member Posts: 1,048
    What furnace model? LP kit? What pressures are you reading?
  • kevsul1
    kevsul1 Member Posts: 23
    It’s a carrier 3.5 high fire 1.8 low 10 inlet
  • ratio
    ratio Member Posts: 3,408
    Those outlet pressures don't sound like LP numbers. Did you change the spring in the gas valve when you changed the orifices?
    delta T
  • SuperTech
    SuperTech Member Posts: 1,919
    That's correct pressures for natural gas, not LP. You would probably want around 10-11" w.c at high fire for propane. And the spring needs to be replaced before setting the pressures. Usually the new one for LP is red.
    You run the risk of completely trashing your new furnace by sooting up the heat exchanger at those pressures for LP.
    DZorodelta T
  • kevsul1
    kevsul1 Member Posts: 23
    Good lord idk why I’m thinking of natural gas pressures thanks for pointing out my stupidity