# Forum Home Renovation Heating & Cooling  Air Conditioner - wall brackets or concrete slab?

## csdaly

Hi all.  I'm looking at a split system air conditioner.  I thought I'd have to have a concrete slab laid, but the installer mentioned affixing to the brick wall with brackets.  Are there any thoughts on whether wall brackets or placing on a concrete slab (on bricks or the like to keep off the ground) would be best?  The reason I ask is that I thought you'd need a certain spacing from the wall.  Thanks.

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## Brian7886

i put most on wall brackets. Even down low.  
Keeps air flowing around them (from under etc), easier to keep clean, makes life easier if you have to mow around it or whatever as well as less chance of vermin or insect activity. They dont weight much so they arent straining your wall at all

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## davegol

ours (fairly big unit) is on 2 concrete pavers - around 400x400 pavers I think. just roughly leveled on the ground.
slab not needed.
i'd be worried about noise transferring into the house if attached to wall .. maybe .. or maybe that's not a thing ?

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## phild01

I reckon noise would be audible if trying to sleep.

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## Brian7886

> I reckon noise would be audible if trying to sleep.

  i have 2 mounted behind my bed on the brickwall behind. Cant hear it or feel any vibrations.  
All our ducted systems we would mount on slabs purely because of weight and size, as well as they are generally a bit noisier.  
Most split systems or similar outdoor units all you can typically hear is air noise from the fan, this cant be avoided.

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## Bros

I accept that this is normal but I would be somewhat hesitant as everytime I have attached anything to brick is doesn't seem to stay in place as the brick is soft and full of holes.

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## Brian7886

> I accept that this is normal but I would be somewhat hesitant as everytime I have attached anything to brick is doesn't seem to stay in place as the brick is soft and full of holes.

  ive never lost 1 yet haha

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## phild01

> i have 2 mounted behind my bed on the brickwall behind. Cant hear it or feel any vibrations.  
> All our ducted systems we would mount on slabs purely because of weight and size, as well as they are generally a bit noisier.  
> Most split systems or similar outdoor units all you can typically hear is air noise from the fan, this cant be avoided.

  Understood but if it is on a single skin wall, it could be a problem.

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## Brian7886

> Understood but if it is on a single skin wall, it could be a problem.

  
all i know is ive mounted 1000s on walls, brick, double brick, single brick, hardwood whatever. Never had a complaint.  
The biggest thing is people think of air cons as being noisy rattling things. New technology, they arent.

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## commodorenut

I've had both, and each have pros & cons.   
At my old place, the wall mounted main unit was 60kg, and it's still hanging on, some 15 years later, with not even a hairline crack in the bricks.
In my current place I have 3 units all wall mounted.  A large Fujitsu inverter, which is quiet as a mouse - no noise through the wall, and the neighbour's bedroom is only 4m away, and they reckon they can only just hear it if they open the window at night.   The bedroom & home office ones are Kelvinator jobs (non inverter) and they do rumble a little through the wall when the compressor cycles on & off.  They are significantly noisier when standing near the outside unit too. 
For this reason, if using a non-inverter one for a bedroom, I prefer a slab (like my old place) as there's absolutely no noise.  Mine was raised, isolated from the house wall by foam expansion strips, and in a garden bed with only ground cover, so it didn't have any ill effects as far as airflow.  It was still under the eave, so frosty mornings weren't too bad as far as the de-icing cycle.

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## Marc

> Hi all.  I'm looking at a split system air conditioner.  I thought I'd have to have a concrete slab laid, but the installer mentioned affixing to the brick wall with brackets.  Are there any thoughts on whether wall brackets or placing on a concrete slab (on bricks or the like to keep off the ground) would be best?  The reason I ask is that I thought you'd need a certain spacing from the wall.  Thanks.

  The concern about airflow may come into consideration with very large units that need to be some distance from the wall. The smaller units work even if a couple of inches from the wall. Hanging from the wall if done properly is not a problem. We have 4 units some older some new, different sizes and all are on brick walls and no one came off. Actually one did one week after installation it fell off the brackets and was hanging from the pipes. The shop called in another installer who fixed the blunder and it is still there pumping away.  
You did not mention anything about noise, but noise from the outside unit is rather irrelevant to those who are inside since the noise from the inside unit would drown it completely unless it is an old rattler that needs replacing. 
Noise would be a concern for complaining neighbours if you intend to run it all night long, something you are not supposed to anyway. 
We had tenants next door who run an old window rattler day and night and no amount of reasoning nor letters from council made them desist. 
So I rung the owner and told him I would pay half of the cost of a new Fujitsu unit providing the window rattler was disabled.
It worked like a charm and I don't hear the wretched thing anymore.

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## PlatypusGardens

Our bedroom and office units are mounted on brackets on the wall.
Hardwood stud house with fibro cladding.
No issues with noise, 
Modern units are well balanced and quiet.
The brackets they use will provide adequate spacing from the wall.   :Smilie:

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## csdaly

Thanks all - very helpful observations. Didn't think about noise / vibration.  But, as mentioned by posters, I suspect it's a relatively small and quiet unit (only serving three rooms).  It would be not far from one of the kids' bedrooms, but that one could sleep through an earthquake.  Neighbours' closest bedroom would be 15 metres away.  And I'm happy with avoiding the cost or work involved on a slab.

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## Brian7886

Most air con installers would install pre cast slabs. Not actually pour them  
Sent from my iPhone using Tapatalk

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## phild01

I only mentioned noise in case it is run in the dead of night and your sleeping head is against the wall, something that I wouldn't like.  Then again the head unit noise would completely drown that out.  Thinking about it again, I am talking #### :Doh:

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## Brian7886

> I only mentioned noise in case it is run in the dead of night and your sleeping head is against the wall, something that I wouldn't like.  Then again the head unit noise would completely drown that out.  Thinking about it again, I am talking ####

  you are right about the indoor unit. modern domestic air cons do not vibrate and rattle. the compressors only have a very faint hum thats almost a whine and usually the condensor fan is louder anyway, which as it is pushing air, is unavoidable

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## Bros

> I only mentioned noise in case it is run in the dead of night and your sleeping head is against the wall, something that I wouldn't like.  Then again the head unit noise would completely drown that out.  Thinking about it again, I am talking ####

  Just installed a 3.5kw in our bedroom and the noise is incredible (lack of) compared to our old wall unit. One thing the old wall unit did effectively was to drown out external noise which was great when I was trying to sleep when on nigh shift.

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## phild01

> One thing the old wall unit did effectively was to drown out external noise which was great when I was trying to sleep when on nigh shift.

  Yes, many motels need noisy a/c to drown out road noise. I have found that very effective when travelling.
I forgot the brand you installed, Bros?

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## Bros

> Yes, many motels need noisy a/c to drown out road noise. I have found that very effective when travelling.
> I forgot the brand you installed, Bros?

  Mitsubishi heavy industry.

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## Brian7886

> Yes, many motels need noisy a/c to drown out road noise. I have found that very effective when travelling.
> I forgot the brand you installed, Bros?

  Lucky, cos most motels buy cheap nasty @@@@ too haha

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