Boiler makes loud thump

Jessica

I have a boiler system with baseboard radiators. Two weeks ago I heard a loud thump. I initially thought someone on the second floor fell until I heard the smoke/carbon detector alarm from the basement. I ran to the basement, no fire nor smoke but I turned the boiler and clothes dryer off as a precaution. I called the hvac company that installed the system 6 years ago and they advised me to call the gas company to check for leaks. The gas company sent the fire department and they confirmed no gas leaks. The Hvac company came later and checked the unit. He said the unit was fine and couldn't duplicate the cause of the "thump" sound I heard. Yesterday, I heard the loud thump again. I called a different Hvac company to get a second opinion, same thing...the unit is fine and don't know what caused the "thump". He only suggested to make sure the pump continues to run. He said otherwise a steam bubble can form causing a loud pop. I've heard "pops" before but the loud "thump/boom" is frightening.

Any suggestions?

Canucker

WAG? What you describe sounds like delayed ignition. That's not a good thing to have. Do you happen to know what they inspected when they gave your boiler the ok?

Zman

A thump/ boom that sets off a co alarm needs to be figured out.
I would expect the technician to do a combustion analysis and a complete inspection of the boiler.
Have you checked the "find a contractor" section on this site?
If you post some pictures, someone may be able to identify some likely causes. In either event, a qualified service is in order.

Mark Eatherton

I agree with the delay ignition theory. That is the only thing that could have set the smoke alarm off. You need a qualified technician to go through the combustion chamber and clean and adjust and test with an analyzer when done.

ME

STEVEusaPA

Along with the above advice, I find it curious that you said "...turned the boiler and clothes dryer off ...".
It is worth considering a combustion air issue. The clothes dryer can pull a lot of air out of the room and the house. A modern high efficiency clothes dryer can pull all the air out of 1500 square foot house in an hour.
Can you take a picture of your boiler? I would like to see if it has it's own combustion air supply (if so, was it blocked).
Are the boiler and the dryer in the same room (basement, closet)?
Something as simple as letting people in the front door could've replenished your combustion air.
Where are you located? Was it very cold?
Was it very windy?
Snow on the ground, covering the combustion air inlet pipe?
Mention this to the tech. There is sometimes more to a problem than just looking at the unit in the basement.

Jessica

Thank you for your responses. I had a 3rd hvac company to thoroughly inspect the boiler and he also said it was fine and everything was working as it's designed. Each person spent at least an hour testing. 10 minutes after he left, it "boomed". Since it would never make the sound while someone is watching it, I set up a surveillance camera to catch it. I hope this link works...

https://ivdn.tv/wE9JC9

gschallert

holy crap.

Ironman

That's definitely delayed ignition. It could be that the burners are dirty and need to be removed and washed with hot water and blown out with compressed air.

There could also be something wrong with the fuel/air mixture, gas pressure, draft, etc.

You need to get a COMPETENT tech on site who knows gas right away.

Jamie Hall

gschallert said:

holy crap.

Ye gods! Turn it off and follow Bob's advice!

j a_2

Can you take a picture of the boiler...That would help...

j a_2

FYI. Do keep the wall informed on the outcome....it greatly helps the next person

gschallert

Definitely turn it off and get someone in asap, show them that video as soon as they walk in the door.

rick in Alaska

Unless I am mistaken, and I don't do much gas here yet, but isn't that boiler supposed to be on a solid base all the wau across, and not two blocks?
I remember Tim Mcelwain mentioning that.
Rick

Jessica

The hvac guy just installed a spark gas valve and an exhaust damper. He said the motor wasn't working on the damper and someone switched it to manual and had it in the "open" position. He suggested to leave the surveillance camera on it. I will give an update in the next few days.

(Additional info...we live in a suburb of Chicago IL and yes it's cold/windy here. The boiler is sitting on blocks because we occasionally get water backup in our unfinished basement. I also want to add that 3 large, well-known hvac companies in the Chicagoland area all said it was working fine since it never exploded while they were testing it. I wasted $85 on each visit. Thank goodness for this forum...you guys are great with your input.

j a_2

I see. Pics but not the video....Anyway when the gas valve was installed was the outlet gas pressure tested...per spec's? I personally was never a big fan of manual hold open on the vent dampener....I would pull it out and install a jumper....please tell me no one jumped the spill or roll out switch....both are safety items.....shut down the gas but keep the electrical on so the water will continue to circulate thru the house....it will give u less chance of a freeze up....Do get this under control

Tom_133

Jessica,

Honestly, the guys on this forum are great, but anyone who is smart enough to know a boom is bad and throw a camera on it to make sure there family remains safe is an allstar!! Good for you, really, wow, great catch. I have had the same problem in the past and my big fat head was down there when it ignited, like yours it only did it every 10 ignitions or so! That boiler got swapped.

Ironman

If the vent damper was in the manual position, that should not affect the ignition of the boiler. The vent damper is there to save energy by preventing heat from the boiler going up the chimney during the off cycle.

I seriously doubt that your problem has been solved.

When did this start happening? Did anyone do anything to the boiler around that time? Are you on natural or LP gas?

j a_2

Of course the vent dampener did not contribute to the boom....it's just an fyi

Jessica

j a...... Here is the link for the video:

https://ivdn.tv/wE9JC9

Jessica

j a...here is the link for the video:

https://ivdn.tv/wE9JC9

j a_2

I saw the video, but did not get the audio

Steamhead

It is possible, though rare, for a bad main gas valve to cause this. I had one once where the main valve would open when only the pilot terminal was getting 24 volts, and it behaved just like that. Replaced the valve and all was well.

JUGHNE

Some Honeywell Smartvalves would do what Steamhead described. I have seen it on furnaces when the pilot and main valve would open at the same time, would "woof" the flame out 1 or 2 times before staying light.
Probably not a Smartvalve on this though. But can happen.

nicholas bonham-carter

Is that boiler a Lochinvar solution which has a more complicated modulating gas valve? I think they are supposed to ignite on low flame, and then ramp up if certain parameters are not met.
Maybe this one is lighting on high flame. Not good--NBC

j a_2

Can you possibly supply the manufacture model number and as well as the model number of the installed gas valve....what exactly was done when the boiler was serviced, were the flame tubes removed and cleaned...was the gas pressure checked and adjusted...also take a close up pic of the gas valve particularly the wiring....it is possible but highly unlikely that a new valve would cause the same issue.....puff....Ask the tech what the gas pressure static and dynamic was...ask him for a copy of his combustion analysis ask him what the outlet pressure was...he should have that readily available to him....one more thing try your best to take a pic of the gas train assembly, where the flames are....but not when it's running....

j a_2

Any updates

j a_2

What happened. Did u fix it

john walsh_2

Is it possible that a chimney down draft is affecting how the pilot light ignites the burners from time to time? From the audio of the video it seems like the pilot lights correctly and before the MV opens, but seems to delay ignighting the gas when the MV does open. I would think that if the pilot was improperly located it would happen much more frequently. I remember looking at a job where the pilot light would extinguish for no apparent reason. After a lot of head scratching, we checked the chimney and saw that it was next to a higher wall of the adjoining building. We added an H cowl and it solved the problem. Just a thought.

Mad Dog_2

Super scary. GREAT CATCH Jessica! I would send those pictures to the the Companies that missed it. No one's perfect, but I think at least one of them would have hung around long enough to catch this. This is one of those teaching moments. You should give yourself Many pats on the back for doing the detective work. I don't think I need to tell you, that you need to find a Very experienced gas service appliance company to figure this out. Keep us posted. Mad Dog

Tim McElwain

I would like to see some pictures of the gas valve and other controls. The boiler needs to have a full pad underneath not cement blocks. The boiler gets its secondary air from underneath. it has been my experience that when the boiler is elevated and not a full pad poured it will cause excessive excess air and poor ignition along with high CO. I need a complete breakdown of controls, location, other appliances in the combustion zone, combustion readings, etc. In the meantime leave it off. I re-read and would suggest getting the dryer away from the combustion zone. What are the measurements of the combustion zone?

Gilmorrie

It seems that the O.P. has left. Hope that she is O.K.

j a_2

I hope as well she is o k....

j a_2

I am wondering if anything changed,

stevieg

I forgot what kind of boiler that is but I remember the configuration and there was a recall on the gas valve, There is also an upgrade kit with a new aqua stat and a whole bunch of other goodies. The gas valve probably wouldn't do this, Most likely the burner tubes are partially plugged and the ignition tube cant do its job. Scary stuff, I have had them puff on me like that and I never stand in front of a gas unit while firing it up. Hope this helps a little. Stevie G.

delta T

stevieg said:

Scary stuff, I have had them puff on me like that and I never stand in front of a gas unit while firing it up. Hope this helps a little. Stevie G.

Rules to live by! I had a water heater that took off one of my eyebrows on a delayed ignition. lit the pilot, let go of the knob, all was well, turned the main valve on, heard gas flowing, but no flame. Thought, huh, pilot must have gone out, leaned down to check and BANG! right in my face. Thankfully the eyebrow is all I lost. It cam back......eventually. Learned my lesson on that one for sure!

j a_2

delta T said:

stevieg said:

Scary stuff, I have had them puff on me like that and I never stand in front of a gas unit while firing it up. Hope this helps a little. Stevie G.

Rules to live by! I had a water heater that took off one of my eyebrows on a delayed ignition. lit the pilot, let go of the knob, all was well, turned the main valve on, heard gas flowing, but no flame. Thought, huh, pilot must have gone out, leaned down to check and BANG! right in my face. Thankfully the eyebrow is all I lost. It cam back......eventually. Learned my lesson on that one for sure!

There are somethings you just can't teach....We ALL learned almost daily.

stevieg

Now as a standard practice I turn the power off to the system and light the pilot, Then switch the gas valve to on, then I can turn the power on when I want to. This give me a little more control over whats happening and I can be a little more prepared for bad situation.

edbradbury

THAT is not normal. Get a gas inspector in right away. That is a serious delayed ignition problem. This is not a 1hr service call. There's a number of things that could cause that condition. You need a gas tech that will look at the whole system not just the boiler. If none of the previous companies checked gas pressures they need a good slap.

Ericmfabc

You expect too much from a company that only charges $XX for a service call,trouble -shoot ,printed combustion test,gas press test,competent tech,ect..