Air Conditioner (Split Unit) Compressor Location

[Gripper]

Hi just back from trip to France & Spain- visited local DIY shed (BricoDepot) saw a split aircon unit for 199 euros. It's a heating/cooling type with two units. At that price I couldn't resist. I'm now planning the install, and despite the instructions and instructional DVD being in French it seems fairly straightforward. My question is : is it possible/advisable to mount the compressor unit (that would normally go on an outside wall) in the loft space? We have a largeish house (6 bedrooms) with a correspondingly large loft. Aside from making the installation easy, it saves mounting an ugly box on an outside wall. The aircon would be used rarely, to heat or cool a bedroom at times, so wouldn't be running anywhere like 24/7. Any thoughts? TIA Neil

[Harry Bloomfield]

Gripper formulated the question :

Generally, no....

Most loft spaces become extremely hot in the summer just from the heat of the sun on the roof. I have seen them loft mounted, but they have been well insulated from the sun's heat and well ventilated.

[mrcheerful]

it puts out hot damp air and maybe even a stream of water, it also relies on cooler air to take the heat away, so no, the loft is not suitable.

mrcheerful (6 air con units at home, plus giant ones at work)

[Andrew Gabriel]

As others have said, no because it won't be able to get rid of the heat. Another factor is there are usually relative height restrictions between the indoor and outdoor units. Check the instructions as you may well find the outdoor unit has to be lower than the indoor unit. (They can be made to work the other way round, but the DIY ones don't seem to be.)

[Bill]

In message , Andrew Gabriel writes

That very point had put me off buying a DIY one for some time until I had a word with an air con' engineer. He said that the main reason for this in the DIY ones was because they relied on gravity to take the water that collected in the inside unit down to the outside where it was evaporated off. Apparently this isn't essential for the operation of the kit, so as long as you can find away of getting rid of the water from the inside unit the outside can be above it. I haven't followed this up yet but it seemed to make sense at the time.

>

[Andrew Gabriel]

I don't think this is the reason. I installed a couple this summer, which required the outdoor unit to be at least 1m (IIRC) below the indoor unit. They didn't pipe the condensate between the units. Also, when buying a non-DIY pre-charged split unit about 10 years ago, I had to specify the relative height of the inner and outer units, and if the outer unit wasn't lower than the inner unit, there was something like an extra £100 cost (and the internal ceiling- mounted cassette evaporator had a condensate pump built in regardless of this). I don't know the reason, but it may be something to do with the gas and liquid phases of the refrigerant, and whether or not they will naturally stay in the right places or need some extra part to force this.

Unfortunately, I don't think many aircon engineers understand the physics/engineering behind the kit they install nowadays (based on the rather few I've spoken to, admittedly). It seems that when they need anything which isn't off-the-shelf, a consultant is brought in to design the system. Then the aircon folks just follow the instructions provided and are completely clueless if the resulting system has a problem (seen this a number of times).

[Bill]

In message , Andrew Gabriel writes

OK thanks Andrew I shall tread carefully then. My situation is that it would be very easy to have the outside unit 1m above the inside due to a flat roof but it would need 10m of piping and a drop of 7m to fit a lower outside unit. I shall keep researching.

[Guy King]

The message from "Gripper" contains these words:

Where would the heat go?

[Gripper]

"Andrew Gabriel" wrote

The unit in question is this one:

the FAQ is this: the two units may be up to 2 metres difference in height. The 2 units have separate drains for condensed water. I plan to install the inside unit on a partition wall between the bedroom and ensuite bathroom, so the drain from that one can fall to the drain from the sink on the other side of the partition. If I do place the other unit in the loft, it will be able to drain into the c/h header tank. I would place it on rubber to isolate noise and vibration. I think the compressor/heat exchanger will be able to dump heat, but obviously not as efficiently as an exterior mounted unit. The loft has good ventilation, and in view of the low usage I think I'll give it a go. If it fails miserably I'll let you know, but it may not be stressed till next summer now. Thanks to all for troubling to reply. Neil

[Andy Hall]

Not a good plan because the tank will eventually fill and overflow. More to the point, the corrosion inhibitor will become increasingly diluted.

[Mike Harrison]

Might be worth checking the manual to see if there is any limit on the inlet air temperature - could maybe have an effect on efficiency if it's too hot coming in

[Pete C]

What? 6 air conditioners in one house...?

[John Rumm]

In our climate, these things can kick out several litres per hour. Won't take long to overflow the tank, or cause corrosian in your CH system.

[Andrew Gabriel]

The outside unit only generates condensate when you are using the unit to heat the house.

It wouldn't work in my loft, which runs at 10-15C higher than the outside temperature in summer. Also, unless you have very thick loft insulation, it would just increase the heat radiating back from the upstairs ceilings, not helped by an additional 2766W it dumps into the loft space.

I wouldn't like to try lifting one of those into the loft either;-)

[marvelus]

Not good enough to disperse the heat one of thoes fukrs gives off!

[dennis]

It would have if you put it next to a grill and used it as an extracter fan. It would cool the loft by extracting the warm air from it.

[Andy Hall]

There are units specifically intended for this application where everything is in one box, including the compressor and evaporator units. There are then fans to force air from outside the house through the compressor section and out again. Ducts on the cold side connect to and from the rooms.

[<me9]

I have mine in the loft. (the external part of a split portable system so it doesn't contain the compressor. It sits behind a set of airbricks and blows outside, ventilating tha loft as well. It does get a bit hot up there, but no worse than it would anyway from the solar gain. I'd like to paint the roof white, but I'm suree the planners would object. It would be much more practical, in summer and in winter.

[Guy King]

The message from contains these words:

Where that idea would fall down in my mind is that the intake air temperature to the "external" unit would get very high on a hot day, which reduces the efficiency of the system. And not just a bit, but a lot.

[marvelus]

Agreed if he has a grill that allows a good flow, I thought he just proposed venting into the loft space in which case the efficiency would slowly drop untill it stopped working.