Loud diverter valve noise with Viessmann Vitodens B1KE-120 Combi

ThinkpadUser7

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

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

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

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

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

yes, and a thermal expansion tank at the combi

ThinkpadUser7

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

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

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

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

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.