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Best base for 6kW Ecodan heat pump external unit

Air Source Heat Pumps (ASHPs)

Last Post by rhh2348 2 years ago

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rhh2348

(@rhh2348)

Estimable Member Member

Joined: 2 years ago

Posts: 102

Topic starter 09/02/2024 1:28 pm [#1367]

What is everyone's thoughts on installation of a unit on earth/ground - seems to be a few schools of thought, around:

Base materials:

level poured concrete - either of:
- one base
- two separate bases/'plinths'
paving slab
gravel

Beneath unit's feet:

nothing - feet sit on concrete/slab
'flexi foot' (e.g. 600mm longh) with struts
anti-vibration mounts under each foot

Securing:

feet bolted directly to concrete/slab
feet bolted to flexi foot and either of:
- flexi feet sat unsecured on top of concrete/slab/gravel
- flexi feet bolted / strapped to / otherwise secured to concrete/slab
feet bolted to mounts, mounts bolted to concrete/slab

Mitsubishi installation manual says two concrete plinths with feet bolted directly to them.

It feels to me that two concrete plinths with unit feet secured to rubber and then rubber secured to concrete is best - the thinking with the last part: to avoid any small unit movements which may impact balance / create internal vibrations or cause small pipework vibrations downstream (unless flexi hoses always cancel this out?).

Do people think securing the rubber to the plinths would bring any benefits (even if small), and if so, which way would you go if you were doing a fresh install?

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Elton

(@elton)

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Joined: 2 years ago

Posts: 59

12/02/2024 3:04 pm

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.

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Elton

(@elton)

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Posts: 59

12/02/2024 3:23 pm

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.

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Derek M

(@derek-m)

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Posts: 4425

12/02/2024 3:33 pm

Posted by: @elton

↑

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'. 😋

👍

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Elton

(@elton)

Trusted Member Member

Joined: 2 years ago

Posts: 59

12/02/2024 3:55 pm

@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! 🙂

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Mars

(@editor)

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Joined: 5 years ago

Posts: 4518

12/02/2024 4:08 pm

@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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rhh2348

(@rhh2348)

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Posts: 102

Topic starter 12/02/2024 5:15 pm

Posted by: @elton

↑

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

↑

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?

👍

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rhh2348

(@rhh2348)

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Posts: 102

Topic starter 12/02/2024 5:23 pm

Posted by: @editor

↑

@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.

-- Attachment is not available --
-- Attachment is not available --

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)

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Mars

(@editor)

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Joined: 5 years ago

Posts: 4518

12/02/2024 5:34 pm

@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.

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rhh2348

(@rhh2348)

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Posts: 102

Topic starter 12/02/2024 5:40 pm

Posted by: @editor

↑

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?

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Mars

(@editor)

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Joined: 5 years ago

Posts: 4518

12/02/2024 5:54 pm

@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.

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rhh2348

(@rhh2348)

Estimable Member Member

Joined: 2 years ago

Posts: 102

Topic starter 19/02/2024 12:36 pm

Posted by: @editor

↑

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...

👍

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