I would say always always always mount on thick rubber anti-vibration grommets in any domestic setting. You do not want to go through it all to find bzzzzzzzzz through your home. I think the new MIS3005 might give some advice on this when released after the consultation as, presently, anti-vibration mounting is required on installations by MCS but a worrying loop hole is the there is zero guidance on what is appropriate. You could literally put something for the weekend 'twixt the unit and concrete base/wall bracket and could pretend that is the anti-vibration mounting. 

Ahh I might be wrong about there being a requirement for AV grommets if the manual says bolt directly to a concrete base. The requirement in MIS3005 is  "4.4.4 Anti-vibration pads/mats/mounts and flexible hose connections should be installed according to the manufacturer’s instructions to reduce the effects of vibration on the building structure." This mixes the expectation there should be AV grommets with the requirements in the installers manual, and if no requirement specified then I supposed they are not strictly required under MCS.

Posted by: @elton

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I would say always always always mount on thick rubber anti-vibration grommets in any domestic setting. You do not want to go through it all to find bzzzzzzzzz through your home. I think the new MIS3005 might give some advice on this when released after the consultation as, presently, anti-vibration mounting is required on installations by MCS but a worrying loop hole is the there is zero guidance on what is appropriate. You could literally put something for the weekend 'twixt the unit and concrete base/wall bracket and could pretend that is the anti-vibration mounting. 

I have found that 'something for the weekend' doesn't actually normally stop 'vibration'. 😋 

@derek-m Haha, this could go on and on past PG to 12 to 15 upwards to 18 by the end of the thread! I will resist the huge temptation to come back with another pun! 🙂

@rhh2348 here's what we did with our heat pump. We secured our heat pump (weighing around 180kg) by placing four levelled concrete slabs side-by-side for a stable base.

Posted by: @elton

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I would say always always always mount on thick rubber anti-vibration grommets in any domestic setting.

Can you give an example or two of such items, and explain why those?

You do not want to go through it all to find bzzzzzzzzz through your home.

Indeed - hence the thread question 🙂 

Posted by: @elton

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Ahh I might be wrong about there being a requirement for AV grommets if the manual says bolt directly to a concrete base.

I did think it odd, particularly as my install came with flexi feet!  Also, Mitsubishi do list those feet in their accessories.

The requirement in MIS3005 is  "4.4.4 Anti-vibration pads/mats/mounts and flexible hose connections should be installed according to the manufacturer’s instructions to reduce the effects of vibration on the building structure." This mixes the expectation there should be AV grommets with the requirements in the installers manual, and if no requirement specified then I supposed they are not strictly required under MCS.

Understood, however I am looking for the optimal approach.  What have you done / what would you do again if you did afresh?

Posted by: @editor

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@rhh2348 here's what we did with our heat pump. We secured our heat pump (weighing around 180kg) by placing four levelled concrete slabs side-by-side for a stable base.

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Wow!

Are they on earth below?

What's the layers between your ASHP and the slab?  (e.g. I think I can see rubber feet under the cabinet / enclosure)

@rhh2348, yeah on earth below, but the area was very heavily compacted so even trying to burrow them in was quite hard. 

Not a huge gap bewteen the ASHP and the slab. It's running now and I'm out tomorrow but I can measure on Wednesday. It is standing in rubber feet. There is zero vibration noise from this unit. It's rock solid.

Base drawing from our manufacturer.

Posted by: @editor

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It is standing in rubber feet. There is zero vibration noise from this unit. It's rock solid.

Niiice.  Which feet did you go for and (how) are they secured to the slabs and enclosure / unit?

@rhh2348 it's the way the heat pump arrived. It was literally taken off a truck, wheeled to the slabs and placed there. It's designed to stand (it's taller than me, and I'm over 6-foot), so no option of wall mounting. Because of it's tall design it's very well balanced, and even when running full tilt, it never reverberates or shakes. Prior to hearing form other homeowners we never even knew that reverberations were a "thing" when it came to heat pumps.

Posted by: @editor

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yeah on earth below, but the area was very heavily compacted so even trying to burrow them in was quite hard. 

This comment has me thinking whether adding concrete/slabs may introduce the possibility of vibrations, when some flexi feet (to raise off ground) on level compacted earth (maybe even sat within a 10mm recess with small drain channel out) may do the job as well if not better...