air conditioning for heating? or separating 1rooms radiators

[greensusie51]

We are looking to heat a flat roofed 5m x 5m x 8ft high extension to our house (already built), which will be used as a study/garden room.(I work from home) it has 2.5m wide double glazed patio doors:south facing.

We want it to be heated seperately from the house, (as I dont want to heat the whole house when I'm working in here all day) and someone suggested an air conditioning unit.

This somewhat confuses me as we want it primarily for heating, not cooling, do air con wall mounted units heat just as efficiently as cool?

Is this more efficient than just extending our gas heating/radiators into the extension or is this air conditioning unit really a viable alternative?


If extending pipes /rads into new extension is the best option is there a way we can separate this room from the main house circulation so we an just have the radiators on in this one room in the day?

any advice on either option appreciated

Look forward to hearing from you

 

[ban-all-sheds]

Aircon will heat as well as cool - when heating they extract heat from the outside air and blow it into the room.

A decent inverting unit will deliver 3-4-5 times the amount of heat into the room as it consumes in electricity.

If you don't already have heating in the room, and as air-con will be very useful in the summer, by the sounds of it, then that's definitely the way to go.

Do not buy a cheapo self-install unit from the sheds - get a proper one and have it professionally installed.

The subject has been covered here, so it's worth a search - IIRC reputable makes include Panasonic, Hitachi and Daikin.

 

[Steve]

Mitsubishi, Toshiba, are other good makes.

dont forget, you will need space on an outside wall for the compressor and outside gubbins. (You say the extension is a flat roof - the compressor can go on the roof if you like)

Expect to pay about £600-1000 for a decent system.

As ban says, they are VERY efficient heaters. a normal electric heater is about 95% efficient. A good air con unit is 400-500% efficient.

 

[greensusie51]

As is takes the heat from the outside air would it make the unit more economical then to position the compressor/gubbins on the flat roof which gets the sun all day (hence warmer air) , better than positioning on the shady east facing outside wall?

 

[racket]

AC is the way to go, the only thing i will point out is the heat that comes out of the indoor unit in the winter is relevant to the air temperature outside, so if the air outside drops below freezing then the heat output also drops. They are better than radiators as you get cooling in the summer

 

[Pensdown]

As is takes the heat from the outside air would it make the unit more economical then to position the compressor/gubbins on the flat roof which gets the sun all day (hence warmer air) , better than positioning on the shady east facing outside wall?

That may help in the winter but it will have a negative effect in the summer when the condenser is dumping heat.

Heat pumps are very good but if the system uses an air cooled condenser there will be times in the winter when you will need supplementary heating. Heatpumps are very efficient down to about 5deg after that they struggle and spend more time going through a defrost cycle than heating the room. If it's going to be your only source of heating you can fit and electric heater battery inside the indoor unit that automatically switches on during the defrost cycle and also when the unit looses efficiency

 

[Steve]

true about the defrost cycle. we have big 3 phase units at work, when it was snowy / sleet in jan/feb this year, every 10 mins they would get clogged up with ice on the back and kick into defrost. it had a very quick defrost though - as soon as the compressor went off the ice started melting. Same with the small DIY one i have at home. I suspect they have defrost heaters in them so the compressor can start up asap. The small one at home still had enough oomph to heat the conservatory though. i was impressed.

 

[Pensdown]

To defrost they go into reverse cycle so basically it's cooling mode without the indoor fan and without the condenser fan. It’s just hot gas being pumped into the condenser coil. The reason they start freezing is in the winter the coil outside becomes the evaporator and as the coil gets cold condensate water forms on the coil (as it does on the indoor unit in the summer) which starts to freeze.

As you say it soon defrosts buts it's a pain when your cold!

 

[TeesdaleSpark]

I've noticed in Norway that Air Con units are quite common for domestic heating. They don't have cheap rate electric either.

 

[ban-all-sheds]

That's why heat pumps are attractive....

 

[Pensdown]

I've noticed in Norway that Air Con units are quite common for domestic heating. They don't have cheap rate electric either.

They tend to use ground condensers which are buried about a 2mts down. This enables the system to work all year round at maximum efficiency

If our government is serious about energy conservation there should be tax breaks for this type of installation because in the short term it's very expensive to install but in the long term it would really help the planet.