# Forum Home Renovation Heating & Cooling  1HP or 1.5HP Window mounted aircon?

## MelbMan

Hi... putting in a new window a/c in a house up near Mildura Vic where it's often mid 40s in summer and quite cold in Winter. 
Looking at a Kelvinator KWH35HRA 3.9kw/3.7kw 1.5HP wallmounted reverse cycle aircon to do a lounge room. The next model down is a 1HP KWH26HRA. The more powerful model is rated 5/4 stars cooling/heating versus 4/3 for the 1HP model
1.5HP = 3900W cooling, 3500W heating (13400/12000 BTU) versus 2800W cooling, 2500W heating (9600/8600 BTU) 
Anyone have these size a/c's and able to make a comment. The 1.5HP is about 60kg and quite large. Having said that the !HP is only marginally smaller. I'm more inclined to go for the 1.5HP unit working on the premise it's better to have a unit of more rather than less capacity. 
I'm going for window mounted because installation is easy and both of these plug into a standard 10amp powerpoint. Kelvinator do not clearly show how many amps each unit draws but I believe its about 5. 
Split systems are too expensive to install in this area being a slightly older house I could be up for a rewire as Powercor are very tough on new installations in Victoria. 
Thanks!

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## murray44

It will draw more than 5A. 
The formula is P(watts) = V(volts) x A(amps). 
The most you can get from a 10A circuit is 240 x 10 = 2400W
Drawing 5A will obviously get you half that, 1200W 
By the way, that's why 99% of household appliances will max out at 2400W (2.4kW), it's the most you can get out of a 240V socket pulling the max 10A.

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## rrobor

Remembering my ohms law, W = I (amps) times V,  so  I (Amps) = W / V so thats  amps  equals watts devided by 240  so if you take the big guy you need to cover 3900 devided by 240 and ooo I think your figures are way too low but there again I thought 1HP was roughly 1000W.

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## Smurf

1HP = 746 Watts. However, the unit will not have a power factor of 1 so a realistic running current is more like 4 Amps or thereabouts.  
Don't forget this is an air-conditioner, not a bar radiator. It will produce somewhere around 3kW output for every 1kW input. You need to look at the input power as far as electrical issues (wiring etc) are concerned but it's the output power, not the input, that determines how well it heats or cools the room. 
For heating, you can calculate this if you know: 
Floor area
Area of external walls and whether they are insulated (including foil)
Area of internal walls to rooms that are not heated / cooled (ignore internal walls to heated / cooled rooms)
Area of windows and whether or not they are double glazed
Ceiling height. 
If all that sounds too much then somewhere around 100 Watts of heating per m2 is likely to be close to what you need for intermittent use (that is, you want to be able to warm the room up from cold in a reasonable time). That's a widely accepted "rule of thumb" here in Tassie and it won't be much different for Mildura from a heating perspective. You can get away with about 70% of that capacity if it's for constant (24/7/365) use so 70 W per m2 in that case. 
The heating output you need will be the same whether you are using air-conditioning, gas, wood, electric, oil or whatever to provide the heat. You are measuring the heat output required from the heater, not how it actually produces heat. 
For cooling it's more complicated due to the impact of sun shining directly though windows on a hot day and I don't have the formula for that (here in Tas nobody really worries about sizing correctly for cooling...). But that said, the required capacity for cooling will generally be higher than that needed for heating in SE Australia especially if there are East or, even worse, West facing windows with no shading. 
How big is the room? Or are you wanting to do the whole house? If it's the whole house and you're only installing a single window mounted unit then I'd get the biggest one you can find and it still won't really be big enough for the whole house if you want it 22 degrees all year round.  
But if just for one room or a smaller area I'd work it out and try to get the right size. Too big is not a good idea at all in terms of performance and long term durability of the unit - best to get the right size.

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## murray44

1HP = 746W,  
You're right Rob, so how does a 1HP unit produce 2.5kW? We need an Air Con expert.

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## shaunos

Hi melbman,
the figures these guys give you are correct, but the Kw/hp rating you've listed is not the power consumption but the cooling/heating capacity which is rated differently to electrical power consumption... ask your supplier how many amps the unit draws etc before purchase, you say that you may need a power upgrade to install a split system?
do a bit of research as an inverter model split system may draw less amps than a window rattler you've suggested (and should comply with meps
regards shaun

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## shaunos

a quick reference i use is roughly 150 watts per square meter of floor area in s/e qld
this is for mainly commercial applications but applied to residentual also

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## chrisp

> 1HP = 746W,  
> You're right Rob, so how does a 1HP unit produce 2.5kW? We need an Air Con expert.

  Refrigerate aircons are heat pumps.  The 1HP is the power in to the "pump" but the actual heat moved can be considerably more.

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## murray44

Thanks Chrisp, I don't know my BTUs from my electrical kW.   :Smilie:

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## exotiic

> It will draw more than 5A. 
> The formula is P(watts) = V(volts) x A(amps). 
> The most you can get from a 10A circuit is 240 x 10 = 2400W
> Drawing 5A will obviously get you half that, 1200W 
> By the way, that's why 99% of household appliances will max out at 2400W (2.4kW), it's the most you can get out of a 240V socket pulling the max 10A.

  You have to remember that the 3.9kW is the output of the model and not the electrical input which is where the formula comes into play. Based on a 5 star rating, I would assume that the system produces within the region of 3kW output per 1kW input at minimum, we can assume that input would be 1.3kW  
Therefore amps at 1.3kW input is 1340w/240V = 5.4A.

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## rrobor

Just goes to show you cant trust numbers no more. When you put one watt in and get 3 out,  EH Jimmy I think theres a wee fiddle going on.   Like in my trade measuring output of an Amp started as RMS. Then went to peak,  then peak to peak, then music power.  Ended up your 2 bob trany was puting out 50W off four tripple A batteries.   Inverter systems dont do it for me. If these things go wrong they do it in style. Inverter supplies are highly efficient as they use high powered  field effect transistors as superfast switches. I havent done ACs but in microwaves its change a rather costly panel or a costly kit and its not uncommon.

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## Smurf

> Just goes to show you cant trust numbers no more. When you put one watt in and get 3 out, EH Jimmy I think theres a wee fiddle going on. Like in my trade measuring output of an Amp started as RMS. Then went to peak, then peak to peak, then music power. Ended up your 2 bob trany was puting out 50W off four tripple A batteries. Inverter systems dont do it for me. If these things go wrong they do it in style. Inverter supplies are highly efficient as they use high powered field effect transistors as superfast switches. I havent done ACs but in microwaves its change a rather costly panel or a costly kit and its not uncommon.

  I don't spend my days servicing air-conditioners but from what I've seen the electronics are the weak point that fails well before major mechanical components such as the compressor.  
I'm a bit reluctant to trash a large corporation on a public forum, but there's a certain _very_ popular brand that hasn't been mentioned on this thread that seem to break an awful lot of control boards. Also they don't seem to perform as well as others when it's really cold outside.

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## elkangorito

Generally speaking, about 5kW (refrigeration power) is the limit before you exceed 10 amps. 18 000 BTU is about the same as 5kW (refrigeration power).

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## commodorenut

> I'm a bit reluctant to trash a large corporation on a public forum, but there's a certain _very_ popular brand that hasn't been mentioned on this thread that seem to break an awful lot of control boards. Also they don't seem to perform as well as others when it's really cold outside.

  I know exactly what you're talking about.  We bought a house with one already installed (mere months before the guy sold the house to us), and still covered under warranty.   
It doesn't perform as well as the other 2 (different brand) splits down the other end of the house in winter, forever going into de-ice, but the external unit is in an ideal spot outside compared to the other 2. 
It's already done 2 control boards within 2 years - both replaced under warranty.   
I dread seeing that flashing LED on it.....

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## MelbMan

Thanks for your posts guys. I went over to Clive Peeters this afternoon who have a sale on until Sun Oct 18 with the intention of ordering a Kelvinator KRH35HRA reverse cycle box a/c, 3.9kw cooling, 3.5kw heating for $649. Just about to sign up and asked the salesman about the standard warranty.. he thought 12 months but it's 2 years. 
While on this subject we got onto other warranties and LG are 5 years.... labour and parts http://165.243.115.15:7001/DATA/WRI/...uly%202009.pdf 
This box a/c is going into a rental so having 5yr cover at no extra cost appeals. On top of this the front panel fitting snuggly on the Kelvinator seems problematic. They seem quite difficult to have the front fitting snugly. Both the one on display at CP and also the Kelvinator cooling only 35CRA I have sitting in my garage sent here instead of a 35HRA 
LG 3.37kw cooling/3.13kw heating is $599 
LG 4.5kw cooling/4.2kw heating is $699 
I think the $699 might be a bit overkill for a loungeroom. 
Any experience, thoughts about LG versus Kelvinator, 5yrs v 2yrs warranty? True the Kelvinator is 5 stars cooling, 4 stars heating v LG $599 3.5/3.0,
$699 model 4.5/4.5 
Service wise there's an LG service agent 200km away in Mildura which is serviced by a daily bus and freight service... about $15 each way. Sounds a long way but when you're 400km out of Melbourne.. Mildura is pretty convenient. 
Thanks John

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## Smurf

LG does not have a good reputation in terms of quality for their products in general. 
That said, my knowledge of LG is for their products in general, not specifically air-conditioners. Their A/C units might be OK (?). 
Personally I'd get a brand of known decent quality. You're only saving $100 or so with the LG and once you factor in its lower efficiency and higher power bills it's not worth the risk in my opinion. 
My own preference would be for a brand like Panasonic simply because they seem to be reliable and I don't like things breaking often.

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## MelbMan

Thanks Smurf... if I was buying a TV I wouldn't consider LG... mainly on hearsay.
Here though it's not saving $100... it's more about warranty and proximity to service centres in a remote country location. So while I wait and see what others hear may think I will give the Mildura service place a call Sat morning and see how they seem service wise. 
Obviously as a consumer you hope not to use a warranty at all  :Biggrin:

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## commodorenut

From my run with them, I'd have no hesitation in recommending Kelvinator A/Cs. 
Can't really vouch for the 'box' units, but the in-laws have had a 2hp Kelvinator split for almost 20 years, and it's still running well, and never given an ounce of trouble. 
I had 2 Kelvinator splits (2.5 & 1.5hp) installed in my old place 10 years ago, and they are still running fine, and apart from cleaning the filters every month & hosing out the coils once or twice a year, they have never needed any attention (the tenants give them a flogging too from the sound of their power bill).
All of the above were made in Oz. 
2 years ago I had 2 1.5hp split Kelvinators installed my current place, at one end of the house (main b/r & study).  They are made in China.  Those 2 splits work far better than the big brand 3.5hp split in the lounge, and the little splits are at the western end of the house too.  As yet, they haven't needed attention, but the 'big brand 3.5 has done in 2 control boards.....

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## MelbMan

Well after mulling on this over night and comparing the LG and Kelvinator brochures I think the main difference between the 3.37/3.13kw cooling/heating LG rated 3.5/3.0 stars v the slightly more powerful Kelvinator rated 3.9/3.5kw cooling/heating rated 5/4 stars is the fact that the LG is fixed speed whereas the Kelvinator has a 3 speed fan. 
So the Kelvinator it is...$649 and I shelled out another $99 for an extended 3 year warranty taking the total warranty to 5 years. $748 versus $599 for the lower capacity and less efficient LG albeit with the standard 5 year guarantee

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## Pulse

Time for a physics lesson... 
did puzzle me too.. 
we all know that energy is neither created or destroyed, well how do you get 3kW of heating (or cooling) from 1kW input?? 
The heat pump simply takes the heat energy from the outside air and uses it to heat the inside air or the inside heat is removed to heat the outside air. 
Anyway thought it might clear up some confusion. 
Cheers
Pulse

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