Warmboard / Lochinvar Boiler Noise

Mister_Mark

We have a new Warmboard system and the Lochinvar boiler makes irritating noises intermittently. Sounds like a harmonic sound within the flue. Any thoughts?
Warmboard hasn't been supportive. Very disappointed.

https://youtube.com/shorts/hvPvSFcql3I?si=qDcpeuxNGknIhQ0B

Radiant23

Is the exhaust and intake piped right. 

I have heard noise from venting when gas pressure is wrong. Had one that was propane. The step down regulator from the tank was 2 feet away from the tap into the boiler. The gas pipe length from low pressure side of regulator to boiler needed to be 10’. Turned out there was not enough propane in the gas line on the low pressure side of regulator and that was what was generating the noise. 

Tom_133

That sounds like a combustion noise. I would call the installer back for combustion test if you dont see the slip that he did it already

psb75

I think you can/should leave Warmboard out of the problem-solving equation. This is strictly a boiler mfg. and installation issue. Check all aspects of the flue venting and intake. Also the fuel piping aspects. Contact the boiler mfg's tech support. I had this problem with a Loch.Noble install that was especially perplexing. The problem was a resonance that was happening at a particular fan speed that occurred when the boiler was ramping up and again when it was ramping down. The Loch. rep ended up reprogramming the motherboard to 'skip' over that particular fan speed. Problem solved.

Mister_Mark

So a little back story. Yes, the boiler is on propane. The boiler uses a concentric vent with an extremely short run of pipe (3 ft). The minimum vent pipe length is 7 ft in the Lochinvar manual (but a 90 degree elbow is equivalent to 5 ft). Warmboard uses Lochinvar boilers that they modify for use in the Warmboard system. We had the Lochinvar rep out to look at the problem. He complained about the Warmboard modifications and blamed a dirty burner or a bad batch of propane. He did check all the burner settings with his equipment. He also swapped a large circuit board for no apparent reason other than a guess. It's difficult to get a company to take ownership of this system because there are 3 or 4 separate companies involved in the various parts of heating system. It's hard to pinpoint who's at fault. My money is on the concentric vent being too short. Warmboard did have a regional rep oversee the installation and give his approval along the way.

A tech did install a restrictor plate in the air vent pipe which fixed the problem temporarily until the warmer weather arrived. So now the problem is back. The restrictor plate is probably a band-aid fix anyway. I should also add that the noise occurs during the startup phase and lasts for around 30-45 seconds.

Here's a picture of the boiler & vent pipe flue. Exterior wall on the left.

Thanks for the comments.
Mark

psb75

My vent was not a concentric. It was a separate exhaust vent and intake. The exhaust was quite short and the intake unequally longer. I also tried constricting the intake pipe to no avail. I replaced two different main circuit boards before the problem was solved. I had the local rep AND the regional rep at the site. It was a crazy amount of resonance (I called it "fog-horning") that was happening. It was waking up the home owners!

Mister_Mark

psb75 said:

I think you can/should leave Warmboard out of the problem-solving equation. This is strictly a boiler mfg. and installation issue. Check all aspects of the flue venting and intake. Also the fuel piping aspects. Contact the boiler mfg's tech support. I had this problem with a Loch.Noble install that was especially perplexing. The problem was a resonance that was happening at a particular fan speed that occurred when the boiler was ramping up and again when it was ramping down. The Loch. rep ended up reprogramming the motherboard to 'skip' over that particular fan speed. Problem solved.

Yes, the noise occurs at startup and lasts for around 30 -45 seconds. Not sure about shutdown but probably then too. Thanks.

Mark

Mister_Mark

psb75 said:

My vent was not a concentric. It was a separate exhaust vent and intake. The exhaust was quite short and the intake unequally longer. I also tried constricting the intake pipe to no avail. I replaced two different main circuit boards before the problem was solved. I had the local rep AND the regional rep at the site. It was a crazy amount of resonance (I called it "fog-horning") that was happening. It was waking up the home owners!

Yes, mine is also pretty loud outside the house. Luckily no neighbors nearby.
https://www.youtube.com/shorts/tbUDT517T-o

GGross

Ask your installer to come back and do a combustion test, make sure it is within spec per the install manual, they have to do this at low fire and high fire. If it makes the noise after it has been properly tested and tuned ask them to unhook the intake pipe from the vent system, if that stops the noise have them change the venting to a 2-pipe termination.

If possible before that run the boiler and go take a photo of the termination while you can see the flue gas coming out, make sure they have the pipes connected to the correct spots.

psb75

I was doing EXTENSIVE combustion tests myself AND with Loch rep on the phone. All numbers were in spec. The regional Loch. rep came out (on site) and did HIS own combustion tests and verified them to be "on spec." "Fog-horning" was persistent. Only after changing "something" on the motherboard back at the regional office...was the problem fixed. It has been fine for 3-4 years since then.

GGross

psb75 said:

I was doing EXTENSIVE combustion tests myself AND with Loch rep on the phone. All numbers were in spec. The regional Loch. rep came out (on site) and did HIS own combustion tests and verified them to be "on spec." "Fog-horning" was persistent. Only after changing "something" on the motherboard back at the regional office...was the problem fixed. It has been fine for 3-4 years since then.

There was an issue that I dealt with on a separate brand, honeywell manufactured boiler controls had something changed in them without telling the boiler manufacturers. Rep had to go around and repair/reprogram and later replace the control on those as well. It was only for LP installs. Foghorn issues can also be caused by other things though so its usually best to rule those out first as the testing/etc needs to be done anyway

HomerJSmith

Did I tell you I hate concentric venting? I hate concentric venting even in short runs like yours. Well, Homer, tell us why you hate concentric venting when the installation manual offers it as an option. Glad you asked. In two words-Gas Reversion. It can destroy a boiler over time. Installing concentric venting on a wall that faces the prevailing winds (windward side of the building) acerbates the possibility of gas reversion. That said.
Lochinvar boilers come configured for Nat Gas and have to be converted to LP. The conversion kit has to match the boiler in which it is installed. That documentation should be in the boiler. The kit consists of an orifice, a fan venturi, and HX plate that is between the fan and the HX. The orifice is directional and must be install in the proper direction and be the proper size for your boiler. It's mumbered. The fan venturi is directional and must be installed in the up direction. The HX plate must be installed with the kit enclosed gaskets. Then a combustion analysis must be done with a recently calibrated combustion analyzer. The inlet LP gas pressure should be 11" of W/C. All this should be doubled checked.
As further diagnostics, I would connect my meter to the LP input and manifold output of the gas valve and start the boiler and check for fluctuations in the gas pressures. The fan has two electrical plugs, a large one on top and a smaller one on the back. When the boiler is running, disconnecting the smaller one, the fan should run at top speed. These are some of the things I would do.

HomerJSmith

A mechanic's stethoscope may help you localize the source of the noise.

Jamie Hall

What happens if you change the length of the inner pipe of the concentrics, just as an experiment? If the pitch changes, then it's a resonance somewhere in the inlet/outlet piping.

Radiant23

I had a couple lochinvar make a rumble noise on start up, maybe not quite the fog horn but definitely noise. Someone suggested drilling a hole in intake baffle. The thought was on low fire start up it was not pulling enough to pull it all the way up for whatever reason. Was a short flu/intake, 2 pipe, not concentric, but definetly has a couple Elbows. It cured a few. Not ideal, but helped. 

GroundUp

How many BTU is the unit? Either way, the venting is too short and it's very likely that the combustion needs to be adjusted. This foghorning typically occurs at a given fan speed and firing rate so if you can pinpoint that in service mode and adjust until the sound goes away, you'll have your problem solved.

Mister_Mark

OK, last week the tech returned and re-adjusted the mixture (richer) and slightly enlarged the opening in the intake restrictor plate. Noise is gone for now. I'm hoping the fix will hold when the really cold temps return next winter.
Thanks for all the ideas.