Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Noisy Boiler

DJDrewDJDrew Member Posts: 47
My wife was in the room above the boiler and nearly jumped up a few floors and through the roof when it started making this noise. Oddly, the noise sounds like it's coming from the gas valve, even though it's probably a bad pump.

I sent a video to the guy who installed the boiler, he's coming to look at it soon.


  • JohnNYJohnNY Member Posts: 2,443
    There's a wire touching something somewhere that shouldn't be. Or a loose terminal....something like that. I've had this many times and it's always something annoying and stupid.
    For troubleshooting and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    John also oversees mechanical installations and maintenance for metro-area clients with his family's company, Gateway Plumbing and Heating along with his brother/business partner.
  • STEAM DOCTORSTEAM DOCTOR Member Posts: 1,164
    Could also be a faulty gas valve.
  • JUGHNEJUGHNE Member Posts: 6,910
    edited October 2019
    Or isolation relay chatter compounding the gas valve chatter?
  • HVACNUTHVACNUT Member Posts: 3,356
    > @JUGHNE said:
    > Or isolation relay chatter compounding the gas valve chatter?

    Or no isolation relay and two 24v power sources butting heads.

    Do you by chance have warm air heat, or is it baseboard?
  • DJDrewDJDrew Member Posts: 47
    HVACNUT said:

    Do you by chance have warm air heat, or is it baseboard?

    We have cast iron radiators all over the house. The strange thing is, it seems to be intermittent. At least I got it on video a few times so when a tech visits, they won't think I'm making something up.

    It's the factory setup with the HydroStat 3200 Plus, no domestic hot water or zones, just a single pump.
  • DZoroDZoro Member Posts: 1,035
    I'd say check wires and change the board. Keep the old board. The flames don't seem to change during the chatter. Try that first but wouldn't be surprised if it is the gas valve either.
  • ZmanZman Member Posts: 5,830
    JUGHNE said:

    Or isolation relay chatter compounding the gas valve chatter?

    This is what it sounds like to me^^^^, unless your neighbor is working on a small outboard motor :D
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • gfrbrooklinegfrbrookline Member Posts: 610
    Try tapping on the gas valve, I had the same sound, tapped it with my palm and it stopped immediately. It comes back intermittently but the same tap fixes it, something inside the box is rubbing on the housing.
    rick in AlaskaDJDrew
  • mattmia2mattmia2 Member Posts: 1,306
    maybe burned contacts in the t-stat arcing which is energizing the valve in time to that arc?
  • CantabHeatCantabHeat Member Posts: 23
    edited October 2019
    Had a noise like that once from the boiler. Was super loud. Turned out a bit of insulation on a wire got cut a bit and bare wire was grounding to the boiler cover. That in turn was causing the 24v relay to vibrate off and in at about 60 Hz. Because the relay was mounted onto a section of the sheet metal surrounding the boiler it was beating it like a drum and thus was making a VERY loud noise. Once I found the problematic wire it was a quick fix.
  • DJDrewDJDrew Member Posts: 47
    Update #1, the tech that installed the boiler in 2017 came and noted two issues:

    1) The circulator was acting up. So that was replaced under warranty.

    2) The bulk of the noise was coming from the gas valve. Tapping it on the side seems to make it go quiet, however the firing rate of the valve wouldn't stay set. You can actually observe a large fluctuation occurring with the flames and it sounds like a windstorm through the flue even thought its not windy. The other two gas appliances, Hot Water Tank and Dryer do not seem to have the same issues with flame fluctuations.

    The tech was going to talk with Slant/Fin and then come back to run more tests on the gas line to the house before just replacing the gas valve.

    Luckily it seems most is covered under Slant/Fin's parts warranty, so it's just the labor I'm paying for right now.
    DZororick in Alaska
  • mattmia2mattmia2 Member Posts: 1,306
    I'd put a voltmeter on the solenoid terminals of the gas valve, preferably analog and see if the voltage is fluctuating in time to the output along with a manometer on both the inlet and outlet before replacing the valve.
  • Keith MKeith M Member Posts: 78
    Please ask your contractor to contact John of Slant/Fin's technical service department. Phone is 800 873 4346 and John's extension is 455.
    Thank you,
    Keith Muhlmeister
    Slant/Fin Corporation
  • DJDrewDJDrew Member Posts: 47
    edited November 2019
    All, Thank you for your input!

    Just as an update, the gas valve was replaced and the boiler has been running quietly since.

    That said, I may be calling the company out to re-tune it, I don't think they set it correctly - even though his analyzer said it was running at 82% efficiency with the new gas valve.

    Our gas meter sits conveniently inside the basement, allowing me to write down the daily usage and compare it to the thermostat log and outdoor temperature during the cooler months (I know, it's dorky.) Since the new gas valve was installed, I noticed unusually high gas usage for this time of year and climate; So I clocked the gas meter when it was the only appliance running and it seems to be running at 6 feet per 3 minutes, when the manual says 3 minutes should be 5.25 feet.

    I really hate to call them back out, but I don't think running the boiler at a higher rate is needed or a good thing to do.
  • ZmanZman Member Posts: 5,830
    The efficiency number on the analyzer is not what you should be looking at. Can you get the results of the test?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • retiredguyretiredguy Member Posts: 220
    I always considered that "clocking the gas meter" as we called it was just a rough indicator of the actual firing rate. Although it is not an exact indicator of the input it is a decent way for the home owner to check the gas input of an appliance. That said, the 6 cu. ft in 3 minutes is approximately 120,000 BTU input and the 5.25 cu.ft is about 105,000 BTU input.
  • DJDrewDJDrew Member Posts: 47
    Thanks @Zman and @retiredguy for the thoughts. I wasn't able to be there to see the screen when he was running the test after installing the new gas valve, but when I talked with him this morning he said it was tuned to 3 ppm co and 6.7 percent o2, cant he remember the temp but it was low range of within tolerances.

    I just double checked it mid-cycle and it was burning 6.25 per every 3 min. This is different than when I clocked it last year at ~ 5.25)

    From talking with him this morning, he said he wasn't too concerned about the noted high gas use reading on the meter because the numbers were good when he tuned the gas valve.

    (Easy for him to say, however it is my gas bill that is going to be noticeably higher!) Ugh.
  • JUGHNEJUGHNE Member Posts: 6,910
    Higher firing will heat your water quicker...less running time and tuned up better.
    Just like driving faster after your car is tuned will get there quicker and if the tune up helped efficiency of the car, you might get the same MPG. IMO
  • DJDrewDJDrew Member Posts: 47
    Our system is an old gravity hot water heating system that is now pumped. My guess is the high-mass system is so slow to respond, that the higher firing rate isn't enough to speed it up.

    I have also noticed the water temps leaving the boiler have increased a little faster, but the system run time log hasn't registered much change with the higher firing rate. The system does overshoot a little more now.
  • JUGHNEJUGHNE Member Posts: 6,910
    Have you tried a shorter cycle time for the Tstat?
  • IronmanIronman Member Posts: 5,626
    Had a bad Hoeywell ignition control cause the aquastat relay to do that on one a while back. Disconnect the 24v coming from the aquastat to the ignition module and see if it stops. If so, then reconnect it and unplug the gas valve. If it then continues, the ignition module is bad.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • ZmanZman Member Posts: 5,830
    Those combustion numbers sound reasonable. What is the boiler aquastat setting and has anyone changed it? You can try turning it down a bit and see if it helps with the overshoot, it should help with overall efficiency as well. Just keep an eye on your return temps, you generally want them >140 to be safe. I wouldn't be surprised if you could turn the boiler down to 160 or so.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • DJDrewDJDrew Member Posts: 47
    edited November 2019
    So there are a lot of radiators on this system, on an average day the return water temp will get to around ~130 before the thermostat is satisfied (This takes around 40-50 minutes based on the weather). On a cold January or February day, the return temp might get to 135-140 after 60-90 minutes running to satisfy the thermostat. The boiler has some protection that was added based on an earlier thread.

    I am not sure there is a way to lower the water temperature much more with this CI boiler. I'll have to look at our thermostat manual (Venstar T1900) to see if it has anything that could help. I remember seeing cycles-per-hour settings and a differential. I am not sure I saw a max cycle time-limit setting.
  • DJDrewDJDrew Member Posts: 47
    edited December 2019
    All, just as a quick update. The tech that installed the new gas valve came back for a free courtesy check after I showed him the logs of higher gas usage. Upon re-checking, he was surprised that I had a significantly higher stack temperature than he recalled calibrating and also noted the higher gas usage in person.
    The tech re-calibrated the gas valve using his analyzer, and we clocked the gas meter. Everything is tuned correctly now. Since I keep a daily log of run-time minutes and gas usage on the meter, I'll hopefully see if the calibration slips between now and the next annual tuneup.
    (We are thankful he came for free check. :smile:)
Sign In or Register to comment.


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