Power requirements for air-con

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Hi,
Having a small sun-room/extension on the back of my house to increase size of dining room. I've been mulling over the idea of adding an air-con unit and decided to go ahead with it.
I've already pulled in a couple of 2.5mm cables to form a new ring main in the extension ready for the sparky - though I only expect to have maybe 3 double sockets in there.
Any reason why the air-con unit can't go on there too? I'd expect it will be no more than 3.5Kw (outdoor unit apparently should be fused at 16A) so the total loading should be fine. However, most switched/fused outlets are only rated at 13A.
Thoughts/ideas?
TIA, Midge.
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13a is plenty for a 3.5 inverter or not...
Cheers
Richard
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Most of the ac units I have wired up in conservatories a 3kW or less and run fine off the ring. I your unit is 3.5kW you will need a seperate 2.5 cable back to the CU on it's own 16 amp MCB with a 20 amp switch in the conservatory.
Adam
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Thanks Adam - I'll check with the guy whose supplying the air-con and see what exactly the spec is.

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Yer what the eff do I know -I've only been in the trade 26 years and had my own company 20.
*plonk*
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r.bartlett wrote:

That's a bit blunt.
Perhaps I've misunderstood something. How many amps are required to drive a 3.5kW unit off UK mains?
Andy
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Amps = Power/voltage
So, for a 3.5kW unit 3500/240 = 14.58 amps.
Adam
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Amps = watts/volts, so taking 230v as the mains supply, and disregarding any power factor correction, 3,500 watts divide by 230 volts = 15.2 amp, but I agree the reply was uncalled for.
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On Sun, 30 Mar 2008 19:27:08 +0000, Harry Stottle wrote:

Indeed.
A further point though: Is 3.5kW referring to the electrical input or the cooling output (which counter-intuitively can be substantially higher)? We have an impressive air-con unit here which uses about 3kW to provide 5.3kW cooling (and 8.3kW heating on the outside) and way would be over the top to cool a single room without significant heat sources.
Peter.
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I'd question if the 3.5kW is the heat pump capacity, and not the power consumption (which would only be around 1kW for that size).
--
Andrew Gabriel
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writes:

A 3.5kW inverter would only draw about 6 amps off the input side.
Adam
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At 583v DC or AC RMS yes - single phase, at 100% efficiency!
Otherwise, any appliance really consuming 3.5kW of UK mains (single ph) will required a 16A feed all for itself.
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Er -- you missed the point.
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Andrew Gabriel
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No but is a lot of duff info mixed up in this thread.
My top ones are:-
1. Oh it'll be okay (it's close enough).
2. Anyone who thinks a 'real' (true) measured quality can increase magically - you are not going to get 3.5kW of anything (heat/cooling/light/sound/movement) from about 6A of 230v mains. - like my chinese computer speakers that say 360w music power on the box - the ones powered by a 9v wall plug labelled 1W (I know, they'll claim peak everything it still isn't close).
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There is nothing magic about it. No one said the 6 amps from the 230V mains will supply all the 3.5kW heating/cooling.
Start with
http://en.wikipedia.org/wiki/Heat_pump
Pure physics. And as Scotty said "ye cannot change the laws of physics"
The OP may get back with the specs of his unit and then we will know what he needs.
Adam
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ARWadworth wrote:

He's not coming back, is he?
16a fuse does indeed sound like about 3.5Kw - and yes, I do know what Watt, Joule, Coulomb and Ampere are - but typically heat pumps have a darn great motor in them so I'd expect a surge current.
I've no idea whether the 3.5Kw is electricity in or heat in. I suspect it isn't heat out.
Andy
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No
So it will be a C type MCB then.

We will never know.
Adam
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Thanks for the replies all.
Sorry - been away for a few days and hadn't expected to spark (pardon pun) such a debate! Still haven't got the precise spec/model but its from Mitsubishi http://www.mitsubishi-aircon.co.uk /
If its a 3.5kw as I think the guy said, it will *probably* be MSZ-HC35VAB or MSZ-GC35VA.
See:
products/m series/r410a wall mounted/classic inverter heat pump/3.5kw
OR
products/m series/r410a wall mounted/inverter heat pump/3.5kw
As soon as I confirm from the quote, I'll post up.
Midge.

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I will have a look later mate.
Adam
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So the 3.5kW is the heat pump capacity, and the power consumption is, as I and others suggested, around 1kW.
The compressor switch-on surge will require 16A protection though, and not too fast acting.
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