Re: Air Conditioning unit advice wanted

[Martin]

One question, How do portable units expel the heat? Most units I have used in the past either have a heat exchanger (and fan) mounted outside, or require a vent pipe for warm air to be blown out, so how does a portable unit which says keep doors and windows closed expel the heat?

I can't take the heat any more! > > Looking at a mobile/cheap air con unit. > > B&Q do a couple (although out of stock at the moment) around £180. > > Product

> Anyone used this before or another similar unit? Any good for cooling

down a 12x12 ft room? > > Thanks, > > Al

[Dave Gibson]

Latent heat of evaporation of water. Room gets cooler, air gets damper.

You get the same effect if you drape wet socks over a fan.

Dave

[Andrew McKay]

I've got one roughly the same size as the one linked by the OP.

If you recirculate the air, forget it - it'll add to the heat in the room. Opening a window and dropping the exhaust pipe out can help, but it doesn't really help much because more warm air comes in the window.

The only solution is a firking great 4in hole thru the outer skin of the house, thru which you poke the exhaust pipe.

But a 12x12 room? No chance. I've got 2 PCs in my study, combined they chuck out about 500w of heat. The mobile aircon just about keeps up, but only just. If I go sit in the study to admire the slightly lower temperature it's over the top. And my study is something like 6x9.

Basically these mobile units are a pile of pooh. Don't bother is my suggestion. I understand from comments made by others that you really need a dual unit, where the fan is inside and the heat exchanger is outside (I hope I remembered that right). Expect to pay a grand or more for something like that.

Andrew

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[Malc]

> Anyone used this before or another similar unit? Any good for cooling

As others have said the water filled ones aren't much cop (although some can be filled with ice) and the portable proper ones don't have much power. A friend of mine has one and it's about 500W or less of cooling. If you think about how much energy it takes to heat a room up then it needs the same sort of power to cool it down. And he has problems sealing around the exhaust pipe (uses towel stuffed around the window).

-- Malc

[John Rumm]

Errr No ;-)

The portable units have a large flexible vent pipe like a tumble dryer - you poke this out a window or through a vent as Andrew says below. If you use a window then you want to open it only enough to accommodate the end of the vent pipe and then preferably "fill in" the rest of the gap (use a towel or wrap the curtains round the gap etc - some units even come with foam batts designed for the purpose)

They will condense lots of water out of the air as well - most have an internal reservoir that needs emptying from time to time. Some you can connect a hose to if you can find a way to have the water run down hill to a suitable exit.

[Dave Liquorice]

Some cheap "air con" units do use this effect and yes they do produce a stream of cool air but as you say the humidity rises. After a few hours your in cool sauna... and your own perspiration can't evaporate either so it becomes really uncomfortable.

Anyway AFAICT the OP is referring to a proper aircon unit as the features specifically mentions dehumidfication of the air, some thing that only happens with a proper chiller unit.

Still need to dump the waste heat somewhere though. Depending on the window design a board with a suitably sized hole would do, but really only works on a sliding type window rather than an opening vent.

[Andrew Gabriel]

That doesn't help -- the air still has to come back in from outside. That's why such units are not as good as two part or fitted units. Someone gave me one, claiming it not to work, which was for exactly this reason. I doctored it to add a second hose which draws air in which is passed across the condensor and expelled again -- this one fortunately had quite separate air intakes for the condensor from that for the evaporator which enabled me to keep the inside and outside air paths isolated. That fixed the problem, but I've never seen one which comes with two hoses for this purpose.

Mine's in a 10' x 12' room with computer and TV, but they probably only total about 200W, and having hacked it, it works quite well.

Indeed.

[John Rumm]

It seems the performance must vary a fair bit depending on the unit.... I have seen powers ranging from 4000 btu/hour to over 14000 for monoblock units.

I use a 8000 btu/h in my office (approx 12'x10'x7'6"). With only 2 PCs on, and me in it, the temp is currently 25.6c. The room next door is currently 32c. It much less humid in here as well.

I would go along with the recommendation for a split unit, although I would not be quiet as disparaging about the monoblocks if you get one with enough power and can put up with the noise (i.e. probably not ideal for the bed room!) Expect to pay 350 quid or more for a decent one though.

[Stuart]

Get a split unit, where the compressor sits outside. Don't waste your money on cheap portables.

I installed one of these a couple of months ago.

Even with todays extream heat, I had to turn the thing down as it was getting too cold indoors.

Stuart.

[JW]

From experience, 8000btu/hr units are not equal. Some will do the job, others wont. I'd have a look on Ebay for a better quality unit.

Oscar

[Andrew McKay]

"No installation required.....".

This is a split aircon, right? ;)

Andrew

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[Al]

It seems the portable units aren't gaining favourable reviews. I'm not keen on having a large floor standing unit on taking up space.

Having spent 5 years in the Middle East, I'm used to full house ACs - a luxury I know!.

I'm keen on the split ACs. The wall units are not as obtrsusive and I have a good place to put the condeser in.

A question about the external condensors - are they supposed to be screwed into the floor/roof? I'm planning on placing it on a flat roof so I can't screw it down.

Thanks,

Al.

[Stuart]

Mine just sits on the patio. I haven't bothered to bolt it down. It's very heavy; you may need a small crane or something to get it up to a roof. Also consider the noise they produce, as it may upset the neighbours.

S.

[Simon Gardner]

They are generally screwed to the external wall - on a frame - actually.

[Matthew Augier (dps)]

I've been looking at these as well, thanks for the extra info... However in the true DIY spirit I was also thinking about somehow using the existing plumbing and radiators to do the job. If you pumped very cold water around the house would this actually generate any coolness from the radiators? Any other ideas for cooling the whole house (split ac's are good but only designed for one room?)

Mat

> Anyone used this before or another similar unit? Any good for cooling

[Simon Gardner]

They certainly aren't only designed for one room.

[Stuart]

The water would have to be so cold to start off with, it would be ice! Think of all that condensation, dripping onto your carpets too!

S.

[Tony Bryer]

From what I can see looking at the pic the two bits look permanently coupled so I presume you hang the compressor outside a window?

[Andrew Gabriel]

They're heavy, but I've seen them blown over on roofs. If it is significantly taller than its width or depth, you want to at least fix it to something with a larger footprint, which also spreads the weight and might help prevent damage to the roof covering. It's best to fix them down if you can. Also think of the vibration coming through the roof -- wouldn't be a good idea if there's a bedroom underneath for example.

[Andrew Gabriel]

You would need fanned radiators, and you would need something to collect the condensate. Then you just invented a fancoil unit. Also, you need to insulate all the pipework very much better than you ever do with central heating, otherwise you will have condensate dripping off every tiny gap or crack in the insulation, looking rather like it's all leaking.