Loud diverter valve noise with Viessmann Vitodens B1KE-120 Combi

ThinkpadUser7 · March 25

I recently had a Viessmann Vitodens B1KE-120 combi boiler installed and there's a loud sound that happens when DHW is first requested while the heat is currently running. I've been told in another thread that this may be due to the diverter valve

I took a video which demonstrates the sound at about the 11 second mark:
https://youtube.com/shorts/d15Pn2WzMAM

The sound is quite audible throughout much of the house and I'm wondering:
1. If this is considered normal and
2. If there's anything that can be done to reduce it

I did have insulation both blown into the walls surrounding the boiler as well as added in the attic above. It might have helped a tiny bit but not much.

Is it possible that lowering the incoming water pressure might help reduce the sound? I believe the reducing valve shows the incoming pressure as 75 psi currently. The specs for the boiler say "Max. operating pressure" is 45 psig, so maybe the water pressure is too high?
(https://www.viessmann-us.com/content/dam/public-brands/us/pdf/technical-data-manuals/vitodens_100-b1he_tdm.pdf/_jcr_content/renditions/original./vitodens_100-b1he_tdm.pdf)

For reference, new system photos are in the second half of this post: https://forum.heatinghelp.com/discussion/comment/1793859/#Comment_1793859

psb75 · March 25

75 psi seems slightly high for domestic hot water. Lower it to 60. The "45 max op. psi" is probably the recommendation for the boiler's system water. That should actually be set to be around 12-16 psi. The relief valve is usually preset to blow-off at 30 psi. European boilers tend to "like" slightly higher pressure than N. American boilers (if there IS such a thing anymore).

ThinkpadUser7 · March 25

Thanks. Yeah, the pressure relief valve for the radiant loop has a gauge that shows around 17psi.

I'm not sure if there's currently a way to lower the pressure of the cold water that enters the Viessmann.

hot_rod · March 26

You should have a pressure reducing valve on your main water line. The entire house gets regulated that way.
50- 60 psi is adequate for most folks. PRVs are factory set at 45- 50 typically.

ThinkpadUser7 · March 26

hot_rod said:
You should have a pressure reducing valve on your main water line. The entire house gets regulated that way.
50- 60 psi is adequate for most folks. PRVs are factory set at 45- 50 typically.

Yeah, I'm pretty sure there's not one currently. There's a shutoff valve where the water line comes out of the ground and enters the side of the garage, and then the line snakes around to various locations in the house via the attic. It's just old galvanized steel piping. I'm assuming it wouldn't be a big job to add one at the point where it enters the garage?

hot_rod · March 26

yes, and a thermal expansion tank at the combi

ThinkpadUser7 · March 26

hot_rod said:
yes, and a thermal expansion tank at the combi

Can you explain how the thermal expansion tank will help in this case? Or is it for unrelated reasons?

Jamie Hall · March 26

If you add a pressure reducing valve -- which might not be a bad idea at all; most of your fixtures will appreciate it -- you also need the expansion tank, as water expands when heated, and without the expansion tank that can create remarkably high pressures unless it can push back into the main line outside -- and a pressure reducing valve means it can't.

Alan (California Radiant) Forbes · March 28

Our local code says not to exceed 80 psi and I don't like to install a pressure reducing valve unless I have to. People like a lot of pressure at their fixtures. I have 90 psi at my house.

I previously - on another thread - said that my V. boiler makes a groaning sound, but it's not a combi like yours and it certainly doesn't sound like that. I doubt that it's from too high a pressure.

What does your installer say? Have him call or text V. tech. support at (800)288-0667 and play them that video.

ThinkpadUser7 · March 28

Alan (California Radiant) Forbes said:
Our local code says not to exceed 80 psi and I don't like to install a pressure reducing valve unless I have to. People like a lot of pressure at their fixtures. I have 90 psi at my house.

I previously - on another thread - said that my V. boiler makes a groaning sound, but it's not a combi like yours and it certainly doesn't sound like that. I doubt that it's from too high a pressure.

What does your installer say? Have him call or text V. tech. support at (800)288-0667 and play them that video.

Thanks for the reply. The audio in the video doesn't entirely capture what it sounds like in person, but you at least can get a sense of the sound level and duration.

I asked about the sound when someone who worked for the installer came out to pick up the check. They said it was normal but perhaps they just didn't want to deal with it. Can I ask V. tech. support myself?

Alan (California Radiant) Forbes · March 28

Normally, they don’t like dealing with the homeowner, but don’t ask, don’t tell. They will want to know model and serial number.

That number also goes through as a text. I would text them your query along with the video.

john_gion · October 23

Hi @ThinkpadUser7, I came across your thread while searching for solutions to a similar issue with my 200-W combi boiler. Did you manage to get it resolved? I’m facing the same problem and I’m not sure what’s causing it. Any advice would be appreciated!

Thanks in advance.

GGross · October 23

https://forum.heatinghelp.com/discussion/comment/1815842#Comment_1815842

Do you have an expansion tank installed and what is the cold domestic water inlet pressure? what is the actual model of the boiler the only current model 200 combi in the US is the 222-f which has a little storage tank and expansion tank built in

ThinkpadUser7 · October 23

https://forum.heatinghelp.com/discussion/comment/1815842#Comment_1815842

Unfortunately, I have not. My new system was installed right at the tail end of last winter and I decided to put off any further investigation until I needed the heating system on again, which should be pretty soon.
If I reach any conclusions I'll be sure to update this thread, and I hope you share anything you learn as well.

I guess my next step is probably to see what Viessmann says.

john_gion · November 10

Hi @GGross, I don’t have an expansion tank installed. The boiler model is a Vitodens 200-W Combi B2KE 30kw, and I’m based in the UK. I don’t have a pressure gauge on the system, but the stopcock is fully open. I tried reducing the pressure gradually all the way down to nearly the minimum, but it didn’t make any difference to the noise level.

Any ideas on what to try next? Thanks for the help!

john_gion · November 10

https://forum.heatinghelp.com/discussion/comment/1815885#Comment_1815885

I had mine installed back in 2019, and I’ve had Viessmann out a few times to check things over. Once was specifically to look into the noise, and the other visits were for replacing faulty parts. I asked about the noise each time, and they kept saying it’s “normal.” They even replaced the diverter valve during the last visit, but that didn’t make any difference.

I’ve also had a few independent plumbers do the annual inspections, and they agreed it was "normal" too. It’s odd, though, because the noise carries throughout the whole house, and I can't shake the feeling that something’s off.

Loud diverter valve noise with Viessmann Vitodens B1KE-120 Combi

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