Sizing an air conditioner

[craigb]

Following on from tons thread, and because it's 42 in Sydney today :eek: , the idea of buying an air con appeals.

How do I figure out which size split system I'd need?

The room in question is about 4m x 5.5m with a 3m ceiling. Leading off this room through a 1.8m wide opening is another room about 4m x 4m.

Ideally it would be good if both rooms could be cooled but I have no idea if this is possible from one unit.

Alternatively, is there a web site that you can plug the figures into and get the answer?

Cheers
Craig

[marineman]

Craig

Best bet is to ring your local air con retailer and tell them the dimensions they should be able to give you the sizing. try with another store as a check.

from the sounds of it you may need something in the order of 15000 btu or slightly bigger.

sorry can't help with web site details
cheers

John

[HavinaGo]

Craig,

Panasonic have an online calculator
http://panasonic.com.au/products/easy_selector.cfm?objectID=24
that will give an initial estimate. As John says, the installers are supposed to do a more complete calculation but my experience was it varies on who you speak to with some more conservative than others. We sized ours conservatively due to the roll off in efficiency as the temperature extremes are reached... check the specs carefully on that one.

http://www.energyrating.gov.au/
... specifically
http://www.worthit.com.au/energylabel/air_srch.asp
is helpful in checking out the efficiency of a device (efficiency being energy output verses energy input .. with care in choice 2kW electrical input should give 6kw output (cooling or heating) ... (they are just heat pumps shifting heat from one place to another --- inside to out if cooling).

all the best surviving the hot

David

[scooter]

Sizing an aircon? I wouldn't have thought they'd be that porous ;) :p

Yeah, I know, sorry and all that !


Cheers........Sean

[craigb]

David,

Thanks for the links, they'll be very helpful.

I fear I've left it too late for this summer.

Even if I bought an air-con today, I'd probably have to wait about two months to get it installed :o

Oh,well, at least it gives me the time to research it properly.

Cheers
Craig

[arose62]

The CoolMax site has a calculator which may help (although they are pushing an evaporative cooler.)

I made a plan of our house, with window sizing and all the facts I could gather, and all the aircon people I've spoken with so far don't even bother to look at it, they just say "You'll need a 1.5 horsepower".

When I find someone who actually says the word "sizing", I'll probably marry them!

cheers,
Andrew

[arose62]

The CoolMax site has a calculator which may help (although they are pushing an evaporative cooler.)

I made a plan of our house, with window sizing and all the facts I could gather, and all the aircon people I've spoken with so far don't even bother to look at it, they just say "You'll need a 1.5 horsepower".

When I find someone who actually says the word "sizing", I'll probably marry them!

cheers,
Andrew

[jackiew]

The CoolMax site has a calculator which may help (although they are pushing an evaporative cooler.)

I made a plan of our house, with window sizing and all the facts I could gather, and all the aircon people I've spoken with so far don't even bother to look at it, they just say "You'll need a 1.5 horsepower".

When I find someone who actually says the word "sizing", I'll probably marry them!

cheers,
Andrew

You get the same thing if you get quotes for ducted heating. They don't even ask if the walls are insulated. Its one size fits all.

[Iain]

The sparky who put ours in said that we could get away with a 1.5hp but a bigger unit would be cheaper to run as it would be more efficient, he was right, we put in a 2.5 reverse cycle and it heats up the room in about 5 minutes and then starts cycling on and off, I was assured that a 1.5hp would stay on a lot longer.
Same applies in summer with cooling.

[Ben from Vic.]

Get the biggest damn unit you can afford (industrial if you have to :) ).

They are often more efficient, as has been mentioned, and on a hot day your unit will still have power to burn ( ;) ).

Also try and get one that has a variable speed compressor, so it doesn't have to go "on off on off on off" to keep temperature.

This type is also more efficient.