Click here to Find a Contractor in your area.
Welcome! Here are some tips for using this forum.
Need to contact us? Visit

low co2 during combustion test

highwayhighway Posts: 7Member
Hello all. First post !! Did a tune up on a friends Thermo Dynamics series 110. Replaced the nozzle with same .85 80B. Pump pressure is 140.  I have an -02 draft over fire and -04 at the breach. I get a 9 to 10 co2 reading at the breach using a bacarach wet kit tester. I cant seem to get the reading any higher. I have the air almost completely shut. I'm I missing something? Thanks...


  • Paul FredricksPaul Fredricks Posts: 1,549Member
    More info

    Is it a Carlin burner in it? If so, what model Carlin. And 110 seems to be a common number for TD. Do you have the exact model number?
  • Big EdBig Ed Posts: 1,086Member
    Air Leaks

    Could also be air leaks dropping the % of CO2 ... Not a great boiler , reading would not alarm me as long a you have a 0 smoke ...
    I have enough experience to know , that I dont know it all
  • AudAud Posts: 1Member
    Draft over fire

    If it is a cwl or an ht, you may  have to much draft over the fire. The settings for Thermo-Dynamics' boilers our listed on the boiler.
  • highwayhighway Posts: 7Member
    low co2

    It has a beckett afg. The boiler calls for a -02 draft over fire, which I have. The chamber liner does have several cracks on the bottom or floor. I have 0 smoke.  Thanks for the replies.
  • billtwocasebilltwocase Posts: 2,385Member
    wet kit

    I would suspect that the fluid needs changing in you tester, as the readings aren't changing. I hope that you did another smoke test, and running a zero smoke. The only poor readings that I've gotten from these are high stack temps, which lowers the efficiency. They are probably the best steel boiler out there other than EK, JMHO. Try a digital tester on it, you may be surprised
  • highwayhighway Posts: 7Member
    edited September 2010
    low co2

    I have a new bacharach wet kit tester with approx 6 tests total. First I checked for smoke and got a zero reading. I then reduced the air and tested again for a trace of smoke. I then checked the co2 reading ( 9 1/2 to 10 ) and then increased the air and tested again for smoke getting a zero smoke reading. I thought it could be the tester, but I checked it on my own boiler when I got home and had a 12 to 13 co2 reading, so I assume the tester is working. My stack temp is 500 *
  • Robert O'BrienRobert O'Brien Posts: 3,024Member

    Leak between the base and HX,fairly common with drybase boilers
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • billtwocasebilltwocase Posts: 2,385Member
    that or

    the flue collector is not sealed. Pull the burner and fully inspect the chamber, back and sides. Look for heat marks on the jacket midpoint
  • Robert O'BrienRobert O'Brien Posts: 3,024Member

    Bill is absolutely correct, i assumed that was checked when serviced
    To learn more about this professional, click here to visit their ad in Find A Contractor.
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!