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New Viessmann Groaning/Resonation

JeremyfromMaine
JeremyfromMaine Member Posts: 20
edited May 4 in Gas Heating
Hey HH Experts,

I recently had a contractor replace a 32 year old oil fired unit with the newest Viessman 100W, B1HE-120 back in November 2021. It looks great on the wall BUT...

Since day one, there has been a series of two groaning vibrations every time the unit turns off and on from heating mode. The living room is above the water heater and I can feel soft vibrations running through the hardwood floor when it happens. I even had a friend come over and ask whose phone keeps vibrating. Let me be clear, it's not a super loud noise/vibration, but I can feel and hear it every time it cycles.

My contractor has been out numerous times and agrees that his other installs don't make that noise and was able to track it down to the diverter valve which they replaced one week ago. Upon installation we cycled it and the noise was virtually gone and he was on his way. However a few hours later it was back to it's usual noise and discomfort level.

It is quite a nuisance because the living room is our main area in the house. Fortunately my contractor has been more than cooperative but hasn't been able to fully fix the issue.

Has anyone else had a similar issue? I'm having trouble believing this is a normal sound for a water heater that's marketed at 'quieter than your refrigerator' on the Viessman website.
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Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,203
    edited February 18
    Your have a real issue that may be unique to your installation. This reminds me of a story about a BlueRay oil fired furnace. This was a failed experiment where the BlueRay Systems Inc developed a oil burner that burned with a blue flame. It was more efficient than the conventional yellow flame we all know and understand. There were thousands of units sold over the few years they were popular. The maintenance was difficult and if not completed properly the furnace or boiler would soot up rather quickly.

    On one of the successful systems the furnace was installed in a basement directly under the living room where the homeowner had a rocking chair that was her normal sitting position for the majority of her time in the home. When ever the burner operated the chair would vibrate with much annoyance to the home owner. No adjustment would resolve the issue. When the factory technical people arrived at the job, it was determined that if the chair was moved to the left or to the right by just 24" the vibration was not detectable. As this was the least costly way to resolve the problem, the factory requested that the chair just be moved.

    The customer was old and set in her ways and did not want to move the chair. So after months of consternation and negotiation, the furnace was replaced with a different furnace of the same specification and model number. The problem was resolved. The factory engineer report concluded the a harmonic vibration inside the equipment was in perfect tune with the structural members of the home directly above the furnace and directly below the rocking chair. The rocking chair acted as an amplifier of the vibration. The replacement furnace flame/heat exchanger combination did not have an identical frequency and therefore the vibration was not detectable.

    I also experienced something called Tank Hum in a fuel tank connected by a copper tube to a Sundstrand model J pump. The customer complained about the noise after I completed the annual maintenance. It may have has a small wafer called an anti-hum device that fell out of the pump while i was cleaning the pump strainer. The fuel tank acted as an amplifier for the vibration frequency of the 1725 RPM gear set in the fuel pump. I was told by the service manager to take a piece of copper and coil it around a coffee can to create a loop and install that loop at the tank valve with the other end connected to the fuel line to the burner I just removed from the tank valve. ...HUM was gone!

    To your point, you have a harmonic hum that is being amplified by something. It could just be that adding a vibration damper somewhere, or a loop of pipe, or bending a fitting, or loosening a screw, or moving a support hanger will interrupt the unusual harmonic vibration that is being amplified to your particular home. I don't think the equipment is at fault... I just think your home is just really tuned in to that heater!

    Edit.
    Try adding a u shaped trap the the piping near the suspect mixing valve, or try a different pump. Process of elimination. one thing at a time

    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    DaveinscrantonayetchvackerIn_New_England
  • Have your contractor text technical support at (844)649-5886 with the model, serial number and problem that you're having. They will give you a case number to keep track of your boiler for any other problems.
    Often wrong, never in doubt.
  • GW
    GW Member Posts: 4,542
    OK I'll try, when 'doesn't' the noise happen? You do have an indirect tank? Can you turn the pump speed down?
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • HVACNUT
    HVACNUT Member Posts: 4,594
    edited February 18
    Is there an indirect water heater?
    You say it happens in heat mode, so assuming it doesn't happen in domestic hot water mode, I would look at the heating circulators. The internal boiler circulator and the system circulator. 
    If it happens even in domestic mode, I would also check combustion. 
    Natural or LP gas?
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    @EdTheHeaterMan it certainly is starting to feel that way, although the harmonic hum is not isolated to one area in the house, but instead can be heard/felt all over.
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20

    Have your contractor text technical support at (844)649-5886 with the model, serial number and problem that you're having. They will give you a case number to keep track of your boiler for any other problems.

    Is that the Veissmann hotline? They actually had a local rep come out a month ago and he didn't have much of an idea as to what the culprit was.
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    GW said:

    OK I'll try, when 'doesn't' the noise happen? You do have an indirect tank? Can you turn the pump speed down?

    The vibration ONLY happens when the water heater cycles on and off from baseboard heating mode. Yes we do have an indirect tank but the vibrations DO NOT happen when it switches over to reheat the tank. Currently the pump speed is at the lowest setting.
  • GW
    GW Member Posts: 4,542
    edited February 19
    I must be slow this morning, I read it three times, seems like you said two different things. Water Heater is or is not related? The reason I ask, we’ve had a couple of noisy indirects recently, which I’ve never seen in the several decades I’ve been doing this

    if I was there, I would be turning various valves slowly towards the off position to see if I can get the noise to change. That would tell me which direction to go.

    Just for the giggles, what kind of water heater?
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • sunlight33
    sunlight33 Member Posts: 377
    I have an older model of 200W, the only thing that can cause vibration is the fan, I don't think any other component in the boiler itself can create that much mechanical vibration. Can you remove the boiler cover and pinpoint the exact location that causes the vibration?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,010
    If I am not mistaken his contractor already isolated the noise to the diverter valve which is doing the changeover.

    Maybe a different valve with a larger CV will work.

    @EdTheHeaterMan

    John Cameron Swayze And the Blue Ray.


    I remember those well.

    I worked in Springfield, MA for an oil co that also had an office in Hartford, CT. The service manager at that time in Hartford was "sold" on blue flame and installed a bunch of them including one in the company owners house. Mostly boilers. I saw there furnace but I don't think I ever saw a furnace installed.

    Equipment that worked in a lab but won't work in the field reliably is a good lesson for everyone and this stuff was proof of that.

    As I recall after a couple of years they came out with a 'Conversion Kit" to change the original Carlin burner back to "yellow flame"

    Most of the complaints were of smell and you would find the burner carboned up.

    If you were one of the lucky ones you could have the burner cleaned twice a year and it would run OK. They had draft issues.

    When the company owner sold the business in the mid 80s my last job for him was to install a new Weil McLain boiler in his house. Since I was starting my own business at the time he had given me a "deal" on a truck and some tools. The pay back was he would buy the new boiler and I had to install it for free.

    Unfortunately for me I not only had to remove the blue ray boiler and install the Weil but I had to remove the old original boiler which "his boys from the Hartford office" left their because they couldn't figure out how to remove it when they installed the blue ray. I took it apart and slid the sections through the cellar window.

    There was only cellar access through his front door, across white carpeting to the door to the cellar which had a turn in the stairs. We covered the carpeting with tarps and plywood. 3 guys 1 long day and never went back.

    A job I would like to forget
    DaveinscrantonayetchvackerEdTheHeaterManIn_New_England
  • Daveinscranton
    Daveinscranton Member Posts: 115
    My great great grandfather grew up starving in the times of Charles Dickens.  Ran a push cart as a child with his father dealing junk off the push cart for a drunkard.  They bought the business.  He eventually became a “metal broker”.  Near as I can tell, that meant salvage yard operator.  Became quite wealthy.  Spent it on alcohol, fast horses, and many marriages.  The rest he wasted.

    He bid a job salvaging a big boiler from a factory.  Got the bid.  Everyone thought that he would lose his shirt on the deal.  Dynamite had become available a few months prior to the job. At 6 am on a Sunday morning he blew the wall off the factory.  Uneventfully.  By 8 am the boiler had been cut loose and was being dragged out by a team of horses.  By 9 am the bricklayers were bricking up a new wall.  By noon, the boiler had been dragged down the street, and sold to its new owner, who was tickled pink.

     I suspect that he was quite good at writing contracts.  I also suspect that things could have gone terribly wrong.  They didn’t.

    The above is clearly off topic.  I apologize.  Ed’s story, which I found fascinating, reminded me of some family history, long ago and far away.

    best wishes 
    ayetchvackermattmia2EdTheHeaterManJeremyfromMaine
  • ayetchvacker
    ayetchvacker Member Posts: 55
    My great great grandfather grew up starving in the times of Charles Dickens.  Ran a push cart as a child with his father dealing junk off the push cart for a drunkard.  They bought the business.  He eventually became a “metal broker”.  Near as I can tell, that meant salvage yard operator.  Became quite wealthy.  Spent it on alcohol, fast horses, and many marriages.  The rest he wasted.

    He bid a job salvaging a big boiler from a factory.  Got the bid.  Everyone thought that he would lose his shirt on the deal.  Dynamite had become available a few months prior to the job. At 6 am on a Sunday morning he blew the wall off the factory.  Uneventfully.  By 8 am the boiler had been cut loose and was being dragged out by a team of horses.  By 9 am the bricklayers were bricking up a new wall.  By noon, the boiler had been dragged down the street, and sold to its new owner, who was tickled pink.

     I suspect that he was quite good at writing contracts.  I also suspect that things could have gone terribly wrong.  They didn’t.

    The above is clearly off topic.  I apologize.  Ed’s story, which I found fascinating, reminded me of some family history, long ago and far away.

    best wishes 
    Now that is what I call a good story!
    Fixer of things 
    Lead Service Technician
    HVAC/R
    ‘09Moto Guzzi V7
    ‘72CB350
    ’83Porsche944
    DaveinscrantonEdTheHeaterMan
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    HVACNUT said:

    Is there an indirect water heater?
    You say it happens in heat mode, so assuming it doesn't happen in domestic hot water mode, I would look at the heating circulators. The internal boiler circulator and the system circulator. 
    If it happens even in domestic mode, I would also check combustion. 
    Natural or LP gas?

    You are correct, there is an indirect tank also from Veissman. The vibrations do not happen when domestic hot water is being called for, only when baseboard heat is being called for. It's a propane system.

    Any other thoughts?
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    GW said:

    I must be slow this morning, I read it three times, seems like you said two different things. Water Heater is or is not related? The reason I ask, we’ve had a couple of noisy indirects recently, which I’ve never seen in the several decades I’ve been doing this

    if I was there, I would be turning various valves slowly towards the off position to see if I can get the noise to change. That would tell me which direction to go.

    Just for the giggles, what kind of water heater?

    There is a Veissman indirect tank, but when that's being called on the vibration does not happen. It only occurs when the baseboard heat is being called on or off.
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20

    I have an older model of 200W, the only thing that can cause vibration is the fan, I don't think any other component in the boiler itself can create that much mechanical vibration. Can you remove the boiler cover and pinpoint the exact location that causes the vibration?

    I've removed the cover and tried to locate it a few times. It certainly is tough.
  • sunlight33
    sunlight33 Member Posts: 377
    So the vibration occurs whenever the unit turns on but disappears while the unit is running?
  • TAG
    TAG Member Posts: 620
    Since the OP is speaking of a "diverter valve" -- he must have one and I assume this is a mechanical valve that sends flow out to the indirect. He is using terms like water heater and indirect .. so maybe be a bit confusing.

    It sounds like the noise is occurring only when the boiler is in heat mode -- going on and off in heat mode. I originally thought he was saying it made the noise when the unit was switching from charging the indirect and moving over to heat mode ... but, it sounds like just on and off in heat mode.

    Can we assume the OP's contractor grabbed the valve when this was happening to see if the noise stopped? Strange harmonic things can occur that make little sense.

    One more. Since I have only used the 200 in a couple projects .... why does the 100 have a valve and not use a direct pump for the indirect? If the OP was saying the noise came from the valve as it was switching away from loading the tank -- I would be changing the speed to see if that helps.

    I have had strange situation in industrial design where components vibrate and they have to be strapped -- or wrapped ... something to alter the vibrations.
  • Peter_26
    Peter_26 Member Posts: 105
    "Happens when unit turns on and off"
    The boiler has a pre and post-purge cycle and isn't this when the fan is running at the fastest speed to clear out combustion gases? Try doing what @EdTheHeaterMan suggested, but to some of the venting pipework. Was the boiler intake and exhaust piped individually or with the concentric one? Where the lengths of the run or runs checked against the I/O manual.

    Pictures?
  • HVACNUT
    HVACNUT Member Posts: 4,594
    Is there an indirect water heater?
    You say it happens in heat mode, so assuming it doesn't happen in domestic hot water mode, I would look at the heating circulators. The internal boiler circulator and the system circulator. 
    If it happens even in domestic mode, I would also check combustion. 
    Natural or LP gas?
    You are correct, there is an indirect tank also from Veissman. The vibrations do not happen when domestic hot water is being called for, only when baseboard heat is being called for. It's a propane system. Any other thoughts?
    Was the boiler set up for propane with the "Commishining Assistant"? 
    Was a combustion test done? I have seen other boilers either not set up for LP when they should have, or combustion numbers were out of range and would howl, and vibrate at lower inputs. The want both high and low fire tests. 400 allowable ppm in the flue is a little ridiculous IMO. Even if this isn't part of your issue, it still should be done. 
    Peter_26
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20

    So the vibration occurs whenever the unit turns on but disappears while the unit is running?

    Yes correct. There's a pair of groans every time the baseboard heating system is called on and off.
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    Peter_26 said:

    "Happens when unit turns on and off"
    The boiler has a pre and post-purge cycle and isn't this when the fan is running at the fastest speed to clear out combustion gases? Try doing what @EdTheHeaterMan suggested, but to some of the venting pipework. Was the boiler intake and exhaust piped individually or with the concentric one? Where the lengths of the run or runs checked against the I/O manual.

    Pictures?

    Can you elaborate a little more on this pre and post-purge cycle? Does it happen just before the heater turns on and just after it turns off? That would correlate with the timing of the vibrations that I'm experiencing.

    It's the concentric pipe and runs 5-6' total with one 90 degree bend.
  • sunlight33
    sunlight33 Member Posts: 377
    Can you take a video of the vibration when the boiler turns on with the cover off?
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    @sunlight33 @Peter_26 @HVACNUT @EdTheHeaterMan here's a YouTube link for a video of my system turning on. With the volume all the way up, you can here the start up groaning at 1:13 and then the second one at 1:16. In real life the groaning has a lower frequency than the video can really pick up as it creates harmonics into the living room above.

    Last night I also confirmed that it does NOT happen when the indirect tank calls for hot water, only when the baseboard heat calls it and then calls it off as well.



  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,203
    If the noise only happens on space heating and does not happen on DHW heating, AND you system is installed according to this diagramthen you should look at the difference in the way the boiler pump follows the different piping paths. What is different in size, length, and route of these two circuits

    Since there is a large pipe connection to the space heating low loss header (G) on your system, illustrated in green, and there is a smaller pipe that appears to connect to the DHW tank illustrated in yellow, there must be a difference in the way the internal boiler pump (A) reacts to the initial start up and the shut down of said pump.

    If equipped... close down the service valves incrementally to the space heating circuit to provide additional restriction to the circuit between the Low Loss Header and the boiler. This will simulate the same pressure drop as the DHW circuit. If adjusting the valve a little each time, you may find a point where the noise leaves but the flow is still sufficient to maintain proper space heat operation.

    That does not cost anything and may find the answer to the problem. With Harmonics and vibration, there is never a sure fire answer. Trial and error until something works. start with the lowest cost adjustment first.

    If you cant get the vibes to stop that way, then a repipe of the Low Loss Header would be my next step. and that is a summer time job!


    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    @EdTheHeaterMan I like where your head is at so I double check the difference in piping between the DHW and baseboard heating loop - turns out they both are reduced coming out of the Viessmann initially, and then transition to bigger piping maybe 12" out from the boiler.

    I also tried incrementally shutting down the service valve between the LLH and the space heating pump without any luck.

    Thank you for trying!

    Here's another video of the overall layout.




  • TAG
    TAG Member Posts: 620
    Don't think the actual boiler fires until almost 1:30 -- sounds like water noise. Could there be air in it.

    What is the radiation -- copper fin or radiators. That's a big LLH
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    edited May 4
    @tag I believe you are correct - it appears combustion doesn't occur until almost 1:30, but you can hear the groaning at 1:13 and 1:16

    It's all standard radiators with aluminum fins in this house.

  • TAG
    TAG Member Posts: 620
    Jeremy: Sorry to create any alarm about the LLH ... I don't see how thats an issue. Also -- I totally forgot about the insulation. I have not installed the insulation for my pumps or the LLH yet ... so my reference on size is wrong. My system uses the smallest 200 boiler and I have the smallest 80/50 LLH ... discontinued.

    If the groaning was the heat exchanger or some other part being hit with lower temp water it would do it all the time ... it's got to be the different flow .... or how the valve is changing the flow as it's moving. Not much else since the noise is occurring outside of the boilers startup.

    I have only used the 200 boiler and it does not have the valve. For mine the indirect tank has its own pump that feeds the tank and the primary loop has another pump ... so my setup needs three pumps. Third for the secondary off the LLH. Can you hold the pipe or valve with some protection and see if the noise changes?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,203
    In looking at your latest video, I have piece together the piping that connects the boiler to the LLH. The picture is the best representation of the pipes from different angles to show that there are no isolation valves where I would think you could close incrementally. It appear there are no valves in that section of pipe.

    If you follow the pipes to the DHW tank, there are at least 20 feet of what appear to be 1" copper. If you follow the piping illustrated you can clearly see less than 8 feet of pipe.

    Adding in the equivalent length of each elbow, you have a different Total Equivalent Length on the Boiler to LLH than you have on the boiler to DHW By restricting the water flow where I have illustrated service valves (by a bow tie symbol) you could throttle restriction equal to the longer DHW circuit. You clearly can not do that with your current setup.

    I believe this illustration will more clearly deliver my idea.

    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    Larry WeingartenJeremyfromMaine
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    @EdTheHeaterMan I appreciate all the effort you've put worth into thinking about and explaining the situation. Yes you are correct, there is no valve between the unit and the LLH
  • GW
    GW Member Posts: 4,542
    Good eye Ed 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
    EdTheHeaterMan
  • TAG
    TAG Member Posts: 620
    ED - So what is that doing ?

    W/O reading the manual -- is there a minimum length required for the boiler loop?

    Do you think there is excessive flow occurring when it heat mode and he is hearing the flow?

    Why does the 100 have the diverter valve and not the tried and true two simple pumps .... I bet the diverter is more $$ and fails about the same
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    TAG said:

    ED - So what is that doing ?

    W/O reading the manual -- is there a minimum length required for the boiler loop?

    Do you think there is excessive flow occurring when it heat mode and he is hearing the flow?

    Why does the 100 have the diverter valve and not the tried and true two simple pumps .... I bet the diverter is more $$ and fails about the same

    Just as a reminder @TAG my contractor has replaced the diverter valve already without any better results.
    EdTheHeaterMan
  • TAG
    TAG Member Posts: 620
    edited February 26

    Yes -- I did remember. Does the manual say anything about minimum length of loop to LLH? Since it's supplied with the primary pump -- it's the correct pump. With the valve being replaced its reasonable to think that two would not have the same problem.

    Have you done all to make sure no air ?

    Mine is piped about the same
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,203
    @TAG & @JeremyfromMaine,

    I am not experienced with this particular boiler. All I am doing is using the fact that when one circuit (which has a longer EPL Equivalent Pipe Length) has on noise or vibration and the other circuit (which has a substantially shorter EPL) has the noise or vibration. How hard would it be to add a ball valve to the problem circuit?
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • GGross
    GGross Member Posts: 114
    I sell these and had a strange situation similar to yours, with the new E series boiler. In my scenario we could not get the diverter valve to actually change positions at all, but the diverter valve would make that groaning sound like the solenoid was trying its best and getting nowhere. If I took the diverter valve out of the unit, plugged it in and used the control to change the valve position it worked fine. Anyway, after many calls to tech support (they also told us change the diverter) we ended up finding a check valve that really did not need to be where it was (but it was in the correct direction of flow, likely slightly stuck), and I am not sure exactly why this caused our issue, but as soon as that check valve was cut out it worked just fine

    The diverter valve in Viessmann boilers very rarely fails, I created a part number a few months ago for the first one we ever sold to replace in the old Wb2 combi boilers that came out in 2003.
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20
    edited May 4
    GGross said:

    I sell these and had a strange situation similar to yours, with the new E series boiler. In my scenario we could not get the diverter valve to actually change positions at all, but the diverter valve would make that groaning sound like the solenoid was trying its best and getting nowhere. If I took the diverter valve out of the unit, plugged it in and used the control to change the valve position it worked fine. Anyway, after many calls to tech support (they also told us change the diverter) we ended up finding a check valve that really did not need to be where it was (but it was in the correct direction of flow, likely slightly stuck), and I am not sure exactly why this caused our issue, but as soon as that check valve was cut out it worked just fine

    The diverter valve in Viessmann boilers very rarely fails, I created a part number a few months ago for the first one we ever sold to replace in the old Wb2 combi boilers that came out in 2003.

    Very interesting. Can you elaborate a little more where in line the faulty check valve was?

    Thank you for the response!
  • That sounds more like a flue issue. Pull the flue off while it's running and see if it changes. If not, try the make-up air pipe. Also, check the piping for any obstructions and where it daylights.

    I know: It doesn't make sense for the flue to be a problem given that the sound isn't there when in DHW, but we're grabbing at straws here.
    Often wrong, never in doubt.
  • JeremyfromMaine
    JeremyfromMaine Member Posts: 20

    That sounds more like a flue issue. Pull the flue off while it's running and see if it changes. If not, try the make-up air pipe. Also, check the piping for any obstructions and where it daylights.

    I know: It doesn't make sense for the flue to be a problem given that the sound isn't there when in DHW, but we're grabbing at straws here.

    Coincidently, my contractor was here on Friday rerouting the exhaust. They removed the concentric pipe and now have separate ones for intake and exhaust.

    Unfortunately the problem still exists, but I like where your head is at!
  • GGross
    GGross Member Posts: 114
    edited May 2
    @JeremyfromMaine

    I believe it was on the return, on the domestic loop. It would not move at all in our case, however the little solenoid on the diverter valve would make a sound for about 1.5 seconds or so, about the same amount of time a phone might vibrate or just a tad longer. It was trying hard to move haha, but generally they are nearly silent, and you should not be able to hear it in another room at all. I will have to get something better to listen to your video, I can't quite make out the sound, it was quite unmistakable in my case.

    EDIT: you can manually operate the diverter valve through the service menu, you can swap it to all 3 positions. If you haven't already done this it may help you to figure out if its the diverter that is causing your noise or something else.