VITOCAL 222-S, how to exclude inverter frequency range to prevent gas pipes resonance.

[Lucas_PdC]

Since a couple of months my flat is heated by a VITOCAL 222-S, AWBT-E-AC 221.C08 together with Energycal Radiant heating elements. I am quite happy with it, were it not for a low frequency hum noise, which becomes most noticeable at night (by neighbors too, unfortunately ...).

For night operation, I have already activated the "Reduced Noise" option, and tried both levels, but not much success. I believe it might be related to an acoustic resonance within the gas pipes (about 13m), which appears to set in when the inverter operates at a frequency somewhere in between 30 to 40 Hz. Is there some way to set some service parameters as to explicitly exclude this frequency range during "Reduced Noise" operation ? Consider also that at nights I do not need full performances, as I set most of the Energycal elements to Radiant operation only (let us say that during night I am probably using not more than about 1kW average).

Thanks, Best Begards

Luca

Alternatively, if it were possible to actually fix a specific inverter frequency value to be held constant during "Reduced Noise" operation, at 20 Hz my plant configuration is extremely quite. Here are the parameters captured when the electric input power is about 1.3 kW:

[Flo_Schneider · Accepted solution]

Hello Lucas_PdC,

if there is a humming noise in the refrigerant pipes, the fastening of the pipes should be checked first. There may be sound transmissions here because the fastenings were not sound decoupled.

It is not possible to reduce the compressor frequency for night operation to 20Hz.

Best regards ° fl

[Lucas_PdC]

Thanks Flo,
indeed, I do not see any such noise decoupling fastening ... it seems the installator was careless about it:
- pipes from the external unit make a curve, but I see no fastening at all before they enter the wall
- pipes to the internal unit come out of underfloor, rise straight up about 220 cm, and make a curve back down to the top of the internal unit. Again, I do not see any fastening to the wall ...
As I now mistrust the way this installator works, I am probably better off by installing said sound decoupling fastening hardware myself. But I have no idea where to get it. Would you have links to examples of suitable fasteners ?
thanks

[Flo_Schneider]

On the following pictures you can see what it should look like. Unfortunately, I can't tell you where you get the fixation clamps from.

But since you are certainly entitled to a warranty on the execution of your specialist company, I recommend that you contact him again. Then he should do the work correctly.



Fastening the refrigerant lines:

■ Only attach the refrigerant lines with pipe clamps with a soft elastic insulation insert (EPDM).
■ Attach the pipe bend for vibration compensation directly behind the pipe bend (towards the outer wall).
■ Refrigerant lines at a distance of max. fasten 2.0 m with pipe clamps. We recommend fastening the refrigerant lines at a distance of 1.5 m using pipe clamps.
■ We recommend installing pipe clamps only on components with a surface weight of ≥ 250 kg / m2.

Best regards ° fl

[Lucas_PdC]

Thanks, I will rather try that myself, as I no longer trust the relevant technical skills of that installator (for other reasons as well), and I am not willing to spend effort in warranty applicability litigations.
I would nevertheless suggest to Viessmann to consider the possibility (for example in one of the future firmware versions) to add the choice for the user to define a fixed frequency for inverter operation, though solely during "Reduced Noise" operation. Of course, making it then clear that that makes sense only when the user accepts a somewhat reduced max power capability in favour of max silent operation.
Best Regards