Weil-Mclain Ultra 80 lp bellows like a sick cow

JohnAshley

We have a 12-yr-old Weil-Mclain Ultra 80 lp for radiant floor heat. Ever since it was new it has gone through phases where it bellows loudly, repeatedly for 10-60 seconds. The plumber has replaced everything but the motherboard, at $$$ per visit, and it still bellows. We're kind of used to the noise now but we are getting ready to sell the house and need to find a solution. Poking around, I found that the noise seems to originate from the aptly-named "air silencer kit," a black plastic vertical tube in the back that's connected to the blower. If I cover the bottom opening in the air silencer while the boiler is moaning, the sound immediately stops and there is a "click" sound. Firmly holding the silencer does not affect the noise. I'm hoping someone else has heard the cows bellowing from the maintenance room and can offer suggestions so I can point the plumber in the right direction. Thanks!

Robert O'Brien

Usually a bad venturi and usually from cross contamination.

JohnAshley

Which part(s) would a bad venturi and cross contamination implicate?

HVACNUT

Is there a yellow sticker on the gas valve stating "THIS VALVE HAS BEEN CONVERTED TO LP GAS"?
Also somewhere on the boiler should be a sticker with the installers name and date of conversion. 
If not, get it checked to make sure. It's a disc orifice. Maybe its sitting in the manual envelope or laying in the bottom of the boiler compartment. 
When was the last time it had a full maintenance, with the WM maintenance kit?
Gas pressures need to be verified and a combustion test must be done. You should get a printout of the combustion test. Its proof for a home inspector to see it's all good. 
Series 2 or 3?

JohnAshley

It's a series 1, annual maintenance and combustion test. Someone wrote "LP" on the venturi in pen. No yellow stickers visible. Orange and white sticker on gas valve, covered by the venturi so I can't see it all, looks like, "WARNING This is a NEGATIVE PRESSURE... REGULATED gas control. Replace... ONLY with same model number..."

JohnAshley

Correction, it's a Series 2.

HVACNUT

The combustion numbers are a little off. As you can see, high and low fire tests should be done. This could be just fine tuning and not related to the noise. 
The maintenance kit comes with necessary gaskets so the gas valve and venturi can be removed and checked. 
It could also be harmonics. WM recommends the use of Sentinel X100 as a corrosion inhibitor and set pH.

JohnAshley

So what does it mean when you say that it could be harmonics? I think we've done everything recommended so far. Not sure where we can go from here. Thanks.

HVACNUT

The boiler only holds .69 gallons. There must be sufficient flow. If the passageways get clogged it can create a bellowing noise. Like a weird ghost. You need boots on the ground to see what's what. 

JohnAshley

I've brought in plumbers from two different companies that install and service WM boilers. Neither one has been able to figure out what's causing the strange bellowing noises. I don't know of any others who work in my area.

Cheeze-Tech

If they haven’t pulled the Venturi I would have them do that. Inspect the inlet and outlet of it for degradation. We had one that made noise only when we weren’t there and that was the issue. Also make sure they are doing combustion test on low and high fire. I’ve had some howling noises as it modulated down from high to low.

TomS

This sounds like a typical "fog horn" problem . First check to see that you do not have a flexible gas line feeding the boiler. If you do, have it removed and replaced with the correct sized iron pipe. Next have the gas pressure checked as well as combustion tests taken while you are hearing the noise. This then may be able to have the noise tuned out while staying within the WM specs. More importantly have your boiler technician call WM tech support and have them walk them through any adjustment procedure and their ideas to eliminate the fog horn noise.

tdoherty

I have a Weil McLain CGM 5 that just started making that fog horn/ howling noise. It starts when the temp reaches about 150 degrees. Had two techs check it. They also suggested harmonics and maybe a chemical add would help. But for an additional $$$ on top of the $$$$ to try and diagnose the noise, I think I need more than a maybe. No one I had check gave a definitive answer. Looking into replacing boiler.

JohnAshley

Tdoherty, that's exactly where we are at. First plumber charged us $$$ and didn't have a clue how to stop the boiler from bellowing. So we brought the second guy in. He recommended maintenance kit for $$$, which didn't change the noise. So then he said the blower was on the way out, for another $$$, and that had no effect either. Now he's saying that we need to replace the motherboard for $$$, but we are running out of money paying for all of these guesses. For what we've spent so far, with no relief, we almost could have paid for a new electric boiler. It's incredibly frustrating.

JohnAshley

TomS, the flexible gas line changes to steel pipe about 6" above the boiler outer case. The boiler was groaning last time the plumber was here to perform the combustion tests, but he was unable to stop the noise. As far as I know, he's never called WM tech support on this.

JohnAshley

Cheez-Tech, I thought they had already replaced the venturi but now I'm wondering.

TomS

https://forum.heatinghelp.com/discussion/164856/csst-the-cause-of-harmonic-fog-horn-noise

Tim_D

Based on the combustion info that you posted it is out of spec and needs to be adjusted. If it has been running this rich since installation the burner may be toast. You have to start at the beginning. Pull the front plate and check the burner and combustion chamber. If that is all good reassemble and check you incoming gas pressure with the unit off and then with the unit on high fire. It should be 11 inches. If it drops considerably when in high fire you may need to address the gas supply. If it is good then continue on to combustion analysis and adjustment. You may also want to check for flue gas recirculation if you find that the venturi is pitted or eroded. Use your combustion analyzer to document the ambient conditions(outside) then put your combustion analyzer in the fresh air piping. If there are elevated levels of Co or CO2 you have a recirculation issue.

topsy

I was browsing this site and couldn’t help but comment on this posting. The bellowing cow sound he is referring to is usually caused by rapid changes being made to the modulation of air flow through the Venturi when the unit is on low fire. This rapid modulation in turn is usually caused by a low flame sensor reading. Most tech people don’t check the igniter because if the boiler fires they assume it’s working correctly. However the igniter also acts as a flame sensor and if it doesn’t sense the correct values within the parameters for low fire from boiler manual it will continuously try to correct the input of air and gas flow causing the bellowing noise that he describes. A quick check of this flame sensor reading could save a lot of time and money.
If values are out of spec it can sometimes be fixed by a quick cleaning of igniter with steel wool or simply replace igniter. Probably to late but hope this helps…..

ayetchvacker

It is difficult to find a good mod/con tech these days. I’m with those who advise replacing the flexible gas connector with correctly sized black iron pipe. I’ve seen this remedy quite a variety of problems. 

Tim_D

Your combustion is improperly set for starters. As mentioned above if there is corrugated gas piping swap it out. Undersized gas piping will also set up a harmonic issue since the negative regulated gas valve, venturi, and blower will try to pull the gas though the piping.