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Let’s discuss my new boiler’s combustion noise...

Timco
Timco Member Posts: 3,040
in THE MAIN WALL
Installed two boilers back to back. Both HTP EFTC140F combi boilers. One customer’s house and one in my own. Same elevation 6 blocks away. Pics later.

Customer Boiler. Vented in 2” 40’ equivalent both pipes. P/S. 1” gas service to boiler room, 36” drop in 1/2” to boiler. Gas pressure is 6.9” and 6.1”. Combustion 9.4% and 30ppm. Terrible fluff at start and hum from blower. New blower and all 3”vent later, still hum on HF and hard start. Swap drop to 3/4”and it’s all solved. Starts and runs perfect. Numbers about the same slightly higher.

My boiler. Connect to existing 12’x3” vents in 2” @ boiler since it’s weekend and no 3” part access. Well within manual distances. Drop 30” in 1/2” here too. My start is prefectly quiet but there’s an audible hum from blower. Prior to setting combustion I swap to all 3” vent and 3/4 drop since it did well at customer. Now odd combustion, hard start, and very audible gas tone that doesn’t really seem to have a source except from the exhaust. 10% and 15ppm. Topped on CO2 but way low CO. On HF it’s opposite, with 9% and 125ppm. Tone is really loud. Crap. Thought this was all for the good of it. So if I throttle the intake back to about 1” opening it runs super sweet. Perfect light and silent. Numbers right in middle of range.

What am I missing??? 1” intake can’t be right....but the back-pressure seems to be the fix. Like it is breathing way too much.
Just a guy running some pipes.

Comments

  • hot_rod
    hot_rod Member Posts: 23,400
    I installed a Lochinvar Nobel in my home recently. I noticed they drill a small hole in the air intake fitting on the back. I know adding that hole solved some of the noise issues on the early Munchkins. It was more of a resonance noise at certain firing range.

    Are you up at altitude or down in the valley? I think you are still in Utah?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Timco
    Timco Member Posts: 3,040
    Yep. SLC proper or about 4210.

    Hey. George at M-One passed. Just saw a note at Hajoca.
    Just a guy running some pipes.
  • Ironman
    Ironman Member Posts: 7,555
    Any CSST in the gas line? That will definitely cause fog-hornning. If so, either remove or enlarge it to the next size.

    I'm not not sure on that model, but on the UFT, if you reduce the gas valve regulator too low, you'll get the "fluff"or no ignition.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Timco
    Timco Member Posts: 3,040
    edited October 2017
    With wide open 3” and 12’ it’s getting all the Air I can want. I’ll try the notch in the rubber boot inside.
    Just a guy running some pipes.
    richant26
  • Zman
    Zman Member Posts: 7,611
    I would put your manometer on the gas outlet port of the gas valve and observe what it is doing as you manually restrict the air flow.
    The amount of gas getting sucked into the venturi is proportionate to the airflow and effected by the amount of negative pressure on the intake.
    I would also listen to the house pressure regulator for a flutter in the diaphragm.
    I agree with Ironman that csst can cause this problem. I have also seen it when the length of pipe between the regulator and the appliance is short.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Timco
    Timco Member Posts: 3,040
    No CSST. All iron pipe.

    Any adjustments above the numbers I gave cause it to spike into the thousands of PPM CO. Have to pull hose off my Insite Plus tester.
    Just a guy running some pipes.
  • Ironman
    Ironman Member Posts: 7,555
    We've seen a lot of them that had to be set to the higher end of the co2 scale to quiet them down. Most of them will go above the manufacturer's CO ppm number when doing that but be below 1/2 the EPA's allowable number.

    It's catch 22. If you're venting, gas piping and pressure are correct, is set it to where it's quiet and ignites properly within co2 specs and forget it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,555
    I just noticed your altitude. I have to ask: does the manual call for any de-rating, adjustments or parts changing?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 23,400
    Timco said:

    Yep. SLC proper or about 4210.

    Hey. George at M-One passed. Just saw a note at Hajoca.

    Sorry to hear about George, he knew more about faucets than anyone I've ever met. Family still involved in the business?



    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Timco
    Timco Member Posts: 3,040
    edited October 2017
    hot rod said:

    Timco said:

    Yep. SLC proper or about 4210.

    Hey. George at M-One passed. Just saw a note at Hajoca.

    Sorry to hear about George, he knew more about faucets than anyone I've ever met. Family still involved in the business?



    I’ll run over and find out.

    I felt really bad when I saw the notice. Haven’t been over there for a few months and had no idea he was slowing down at all. He was in there last time I was there. Said he served in Korea so there’s that. Wish I had said goodbye. Great guy.
    Just a guy running some pipes.
  • rbeck
    rbeck Member Posts: 56
    The gas valves like a bit of back pressure. Most noise problem I have encountered on Alpines, I know a different boiler but very similar operation, has been with very low back pressure. Just for the fun of it block off about half the vent to see if the problem goes away.
    When I see vent pressures below 0.05" w.c. is when I normally get the noise. Just my 2 cents

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