How to reduce the noise from the cylinder of an ASHP system?

Ken2000

I recently had an ASHP system installed in my bungalow, with the main cylinder located in a cupboard in my spare bedroom. 

I hadn't appreciated how loud the whirring would be and am wondering how best to reduce the noise. It's tricky to identify exactly where the noise is coming from, but it's somewhere in the orange circle on the photo. I had considered lining the cupboard with acoustic foam. 

Rodders53

What does GM Boyd your system installer say about it?

You've got at least three water circulating pumps in that cupboard as part of that cylinder with external plate heat exchanger! Plus the motorised diverter/mixing valve.  From the install manual http://www.mitsubishitech.co.uk/01_Ecodan/Data_Monoblock/Cylinder_Pre-plumbed_Slimline.html :

Primary circulating pump (Low Loss Header to Heat Pump return)
Primary circulating pump (Low Loss Header to Heating circuit)
DHW circulating pump
3 Way motorised diverter valve

The only item not in your circle is the DHW circulating pump.

As I read it one pump circulates water to/from the external Ecodan unit and the other does the Central heating.  The 3-port valve selects CH only - CH & HW - HW only.  In the last 2 positions the DHW pump will likely run, too.

Only if HW and CH demands are both satisfied will all three pumps stop.  At all other times two will run and sometimes all three.  I think.

Circulating pumps make some noise - maybe more so when newly installed and dissolved air is slowly removed from the sealed water circuits.  Three port valves usually only make noise when the motor operates to move the valve from one setting to another - just a few seconds in my experience.

This issue of potential noise should all have been discussed before installation, was it?