Re: Air Conditioning unit advice wanted

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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?

http://www.diy.com/bq/product/product.jhtml?PRODID 3935&CATID0440
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how
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
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Dave Gibson wrote:

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.
--
Cheers,

John.

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On Sun, 10 Aug 2003 21:23:15 +0100, Dave Gibson wrote:

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.
--
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On Sun, 10 Aug 2003 18:33:08 +0000 (UTC), "Martin"

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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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.
--
Andrew Gabriel

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On 10 Aug 2003 23:16:47 GMT, snipped-for-privacy@aol.comNEWS (Alex H) wrote:

I love the starting paragraph:
"No installation required.....".
This is a split aircon, right? ;)
Andrew
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McKay wrote:

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?
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Andrew McKay wrote:

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.
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John.

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wrote:

I have one of these from comet - i got it last summer, its a 8000 BTU unit and it drops the temp of my bedroom (4M x 4M) by about 10 degrees. I agree about the vent pipe - you can either use the foam rubber sheet they supply you with but with hinged windows (as against sliding windows) you still end up with huge gaps to let in the hot air and as you the alterntive is a 4" hold through the wall........BUT in a true diy fashion i built myself a window wedge from scrap wood that fits in the opening of the window when its about 1/3 open with a hole for the vent pipe and sealed round the edges with pipe insulation. So not i just need to open the window to it fullest extend, then shut it on the wedge and insert the vent pipe - it makes a good seal all round including top and bottom.......it works great....only problem is it is a bit on the large size but still it works
gin
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http://www.diy.com/bq/product/product.jhtml?PRODID 3935&CATID0440
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
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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. http://tinylink.com/?fgrEyo9D6N
Even with todays extream heat, I had to turn the thing down as it was getting too cold indoors.
Stuart.
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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
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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.
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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.
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snipped-for-privacy@hotmail.com (Al) wrote:

They are generally screwed to the external wall - on a frame - actually.
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     snipped-for-privacy@hotmail.com (Al) writes:

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.
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Andrew Gabriel

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snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote in message

There is a dining room under the flat roof - which isn't used a huge amount. Wonder if the vibration would cause any cracking on the internal ceiling/walls?
In terms of noise - I'm figuring there aren't any noise control laws that would stop me using these? We are in a terraced house and the neighbours bedroom window would be about 10ft away (approx. same level) from where I plan to place the condensor unit.
My main worry (and the reason I asked about fixing the unit) is someone nicking the condensor. The unit would be easily visible from the street - our house is second one in from the street. Do these things get stolen?!
One of the replies in this thread mentioed globalcooling.org.uk. Would be interested in hearing on your experience once the AC has been installed at your place.
Cheers all.
Al.
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     snipped-for-privacy@hotmail.com (Al) writes:

No, just a hum. Imagine your fridge with a compressor some 10 times the power.

I would say that's far too close, given their window is likely to be wide open and possibly trying to sleep in there when your AC is running. Also, they might pick up a large amount of the hot air on occasion.

Not often -- they aren't really any use by themselves. We did have one taken from someplace I worked a long time ago, but we were told that was rather unusual.
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Andrew Gabriel

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On 13 Aug 2003 10:07:45 GMT, Huge wrote:

I my very rough an ready experience of aircon 1kW of heat input to a space needs at least 1kW of air con to keep that space cool.

Something bigger than 9,000BTU or around 3kW. B-) Might have to start thing about a separate spur to provide it's power...
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