Buderus GB142/24 WHISTLING

subcooler_65

I have a 11 yr old GB142 that just began making a loud whistling noise as it heats for H/W. Doing some Google'ling it appears that I might have a boiler thats "Kettling". The whistling sound is not there at burner start up but as it goes to higher flame the whistling starts and increases in loudness as the boiler heats. When the burner shuts down the whistling continues for a few seconds and disssapears. I cleaned the combustion side of the boiler in hopes that maybe thats what was causing the noise but it's still there.
Last night I tried back-flushing the HX to see if anything would come out. The water came out clean and clear with no scale particles with what I think was good flow. I purged this boiler 2yrs ago when I added radiant to a new room...I expected the water to be discolered but maybe this is why it looked so clean.
I can hear that the sound is coming from both the left&right side of the HX. I think my next move would be to flush the HX with a cleaner.....Rhomar 9100?

I'm going to take a video and hopefully get it posted in a bit.

Anyone run into this problem or have any ideas?

Here's a video; https://www.youtube.com/watch?v=tG0ma5vVuAQ

Alan (California Radiant) Forbes

Boiler kettling is a popular topic on this website and it can be difficult to treat, but i think you're going the right direction with a chemical flushing treatment. Rhomar makes excellent products and you may have to do it more than once to get rid of the harmonics.

What kind of heating do you have? Radiators, radiant, hydroair? Also, does the boiler heat your DHW?

subcooler_65

All under-floor Radiant with indirect H/w tank. The Rhomar is about the only cleaner that I could find that was safe with Aluminum HX. Called Bosch/Buderus tech line yesterday and they wouldn't recommend a cleaner.

Zman

How is the system piped. What is the delta T (temp difference between supply and return) when the noise is happening? What is the system pressure.

This could be scaling in the boiler. Low flow or low pressure is also a possibility.

HVACNUT

When was the last time a maintenance was done by a qualified tech?

subcooler_65

Zman, Thanks for responding. System is piped with factory pump manifold, 4zones of heat and DHW. The supply/return Delta T at the boiler (above pump manifold) was 38.3*. The circulator for the H/W is a Grundfos US15-58FC. this is normally set to the lowest speed and with a 153* BT, 75* DHW Tank my delta T is 16.5*. Same temps on Highest speed gave me a delta T of 9.8*. Boiler pressure maintains at 16psi and does not fluctuate at all.

Couple things I noticed while working on it.

The boiler starts the loud whistle at about 180*BT.
While making the whistling, if I switch the DHW circulator to the highest speed the whistling will almost go completely away even as the boiler temp climbs into the 180*s. I tried running a zone of heat and setting the DHW circ back to low and the whistling came back.
I'm still scratching my head, but usually things make more sense to me after I relax with a cold beer.
I have to run out for a bit, I'll post some pics when I get back to make the above a little clearer.

Thanks again.

subcooler_65

HVACNUT said:

When was the last time a maintenance was done by a qualified tech?

Nut,
I have about 20yrs in the field although I've been out of it for about the last 12 or so. This is my own house so I maintain this boiler myself. Been running great for the last 11yrs and hasn't given me any problems. This whistling is a new one for me and I've never come across it before. Always liked being in the trade and solving customers problems but I didn't see a whole lot of these High efficiency units when I was in the field, worked on some and was trained on some but they weren't as popular as they are now.

I'm willing to listen if you have any ideas..al

subcooler_65

Pics

Ironman

Take a look at the dielectric unions where they're leaking (something very common on that boiler). If there's that much minerals on the outside, the inside is probably worse. I'd also look inside the unions, they're notorious for clogging up.

subcooler_65

Mine just started to leak...I've been meaning to order some new gaskets. Not really any corrosion anywhere on the boiler.

subcooler_65

Is there an easy way to disable the OD-Reset so I can try running the heat at a high boiler temp?

Zman

Has a combustion analysis been performed?
The noise does seem like it is on the water side. I would not rule out a combustion issue until an analysis has been performed.
Is the heat exchanger clean on all sides?

Alan (California Radiant) Forbes

I heard the same thing this morning on a Laars JVS that we installed 25 years ago. The sound stops when the burner turns off with the pump still running. Same style of HX; Laars is copper, Buderus is aluminum.

Obvious to me that there's a problem with heat transfer somewhere, either inside or outside the HX. You say you've cleaned the dry side; go after the wet side.

subcooler_65

I don't have a working analyzer at the moment, it needs to have the O2 sensor replaced and I don't want to shell out the 140$ to replace it for 1 time use.
I just thoroughly cleaned the HX so I don't think that's the problem. Seems the noise comes with temperature and not combustion. The noise starts when the boilers north of 180*.

subcooler_65

I asked in my original post but is there any recommendations for a boiler cleaner other than Rhomar 9100 or should I just go with that?

kcopp

9100 is fine. Axiom is another good choice.

You say you are running the DHW circ on low speed... Why?
With DHW you typically want flow through the boiler and coil at a good rate as the coil prob has a decent pressure drop.
I would leave it at top speed.

Big Ed_4

The Fan motor bearings are getting dry , replace the fan motor ...

subcooler_65

So this morning I ran a zone of heat with the boiler temp climbing to 190+ degrees without any whistling noise. Seems my problem is only with the DHW loop. I pulled the DHW circ off to check the impeller and FC. figuring it was plugged with something but it was clean. I reinstalled the pump with new gaskets, set it to high and gave the loop a good purge.
After taking a shower later in the day I went back to the boiler to watch it reheat the tank. The boiler temp climb back up into the 190s without making any noise whether the circ was set to high or low....? I ended up leaving the circ in high and we'll see how it goes.
Wonder if it was some air trapped in the loop...?

Zman

It could be air or the circ is going bad. Sure seems like a flow issue.

psb75

There is also the Buderus-recommended mineral oil spray on the heat exchanger--spray oil and then fire the boiler, then rinse down. There is a YouTube video of it.

EdTheHeaterMan

@subcooler_65 I have found that some equipment Humms and others whistle, I believe it is because it forgot the words. Maybe you need to upgrade the iTunes app.

But @HVACNUT, @Alan (California Radiant) Forbes, @Zman @Big Ed_4 and the other might have a point also

BillyO

sounds crazy but I have had this exact problem with hot water heaters in the past with the corrugated gas line from gas valve to burner. take apart the corrugated gas line in boiler and just reposition it. The noise will go away.

subcooler_65

BillyO, I've heard this before when I used to service propane pool heaters. My problem was the DHW loop. Must of had just enough air in it to slow the flow through the HX. Been working fine now for 2wks...?

subcooler_65

> @EdTheHeaterMan said:
> @subcooler_65 I have found that some equipment Humms and others whistle, I believe it is because it forgot the words. Maybe you need to upgrade the iTunes app.
>
> But @HVACNUT, @Alan (California Radiant) Forbes, @Zman @Big Ed_4 and the other might have a point also

That's going to be a problem..I'm only running Android.....

mrbman7

I know this is an old thread but this is exactly the same issue I have with my GB142 right down to the DHW loop. Wonder if the issue ever came back for the OP? @subcooler_65 care to comment?