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How's This Heat X-changer Doing After 14 Months?

D107D107 Member Posts: 1,687
edited June 3 in Gas Heating
Had annual boiler maintenance yesterday. Was looking forward to checking out CI boiler sections and breeching for corrosion given no bypass--only Circ Hold on Hydrostat. (System is mostly CI rads, so supply and return water temps largely below condensing temperature. Peerless MI-03 50mbh net, with heat loss about 30mbh, so even though boiler is about smallest we could find to match the load, cycles are perhaps still not long enough with low-temp return water to cause much corrosion--I hope. The lack of drippings from sections onto concrete blocks below would seem to indicate that any condensate is evaporating(?)

Photos show some rust on sections--normal?--and no corrosion that I can see on the galvanized breech piping. Chimney liner itself is Stainless steel. I am curious about the strap hanging in the horizontal part of liner.


  • STEVEusaPASTEVEusaPA Member Posts: 4,216
    Draft may be too high, resulting in our low CO2 and high excess air numbers. Also, what was the gas pressure (maybe underfired)?
  • D107D107 Member Posts: 1,687
    edited June 5
    @STEVEusaPA Not sure why the draft wasn't printed on the receipt. (35ft internal 5" chimney liner.) Last time I clocked the gas meter, firing rate was within spec. (70mbh) When I questioned the CO2 and O2 readings, the answer I got was:

    "Local regulatory agencies have guidelines for monitoring NO, NO2, CO, and SO2 gases. Generally, it is required that the concentration of these gases be corrected for the diluting effects of excess air. The amount of excess air is determined from the O2 concentration measured in the flue. The measured O2 concentration, together with the O2 reference value is used in the equation below to obtain the corrected gas concentration. O2 reference values of 3 and 6 percent are often used, giving a corrected gas concentration equivalent to that at oxygen concentrations of 3 or 6 percent. When an O2 reference of zero is used, the gas concentration is referred to as undiluted or air free."

    So based on that I was told that the readings were good. I can't say I really understand that too well. If the draft was too high, given this has en electronic vent damper and no barometric, I don't know how one would adjust for that. Can a barometric damper be added?

    Boiler sections look ok?
  • ZmanZman Member Posts: 5,872
    What model boiler?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • D107D107 Member Posts: 1,687
    edited June 6
    @Zman Peerless mi-03
  • SuperTechSuperTech Member Posts: 1,344
    edited June 6
    That boiler has an integral draft hood, Peerless doesn't recommend using a barometric damper.
  • ZmanZman Member Posts: 5,872
    edited June 9
    Those can be a little tricky to get an accurate reading due to the proximity of the integral draft hood to the burners. Did they stick the analyzer in the vent pipe or the boiler itself?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 5,872
    The heat exchanger and vent look great!
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Tim McElwainTim McElwain Member Posts: 4,374
    I recommend with the vent damper and built in draft hood that holes be drilled in the front of the draft hood so the probe for conducting Combustion Test can be accurate. Sticking the probe after the vent damper or attempting to get it up inside the draft hood can lead to errors in excess air and all the other readings. Drill the holes and stick probe into each section one at a time and average the readings. Get some decorative metal inserts to plug the holes drilled after you are done. Your readings will much more accurate.
  • D107D107 Member Posts: 1,687
    edited June 8

    @Tim McElwain @Zman
    1-In this case I think he put the probe inside the boiler--see photo. We do have one hole drilled right above the damper filled with a bolt. What do you guys use for hole inserts?

    2-The explanation on the readings--a bit beyond my comprehension--seems to say that the readings are mitigated by calculating in the effects of the excess air. I've never heard of a formula to be applied afterwards to the readings.

    3-Good to know @Zman you feel the HeatX looks fine--I see the rust but it might have been installed that way if it was lying in a warehouse for awhile. What would I be seeing if there was corrosion? Since there is no bypass, in some earlier posts you and @SuperJ came up with some great ideas on three-way valves and circ swapping etc which I greatly appreciate. Good to know that they likely won't be needed but available if we ever do.

    4-On the Field Control vent damper: installer replaced the defective one--the motor was fine but the damper itself was getting stuck. He showed me how even the new one was not perfectly in round. They're great devices, just wish they could be made a little more sturdy. He also showed me how the chimney guys put the breeching slightly downward into the stainless steel chimney liner.

    5-2-3X last summer the Vent Safety Shutoff Switch engaged with no apparent cause. Chimney inspector thought that it could be due to hot/humid temps outside PLUS the hot basement temps due to dehumidifier putting out hot air in boiler room.

    6-Anybody recognize that strap inside the liner from the earlier post photo?

    All in all the boiler is working fine, and definitely saving me $$ over the prior way-oversized model that had no spill switch, vent damper or low-water cutoff.

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