£7-£8k for Aircon system

danrv

Reed_Richards said:

ASHPs can be air-to-air or air-to-water.  The former is more commonly known as air conditioning but an air conditioner that uses a heat pump will be vastly more energy efficient than one that doesn't and not all air conditioners have a heating mode.  So an air-to-air heat pump is an air conditioner but an air conditioner is not necessarily an air-to-air heat pump. 

Thanks.
That’s what I was a bit confused about. So a cooling only system would use a unidirectional unit. Not sure what this would be called.

QrizB

Reed_Richards said:

ASHPs can be air-to-air or air-to-water.  The former is more commonly known as air conditioning but an air conditioner that uses a heat pump will be vastly more energy efficient than one that doesn't and not all air conditioners have a heating mode.  So an air-to-air heat pump is an air conditioner but an air conditioner is not necessarily an air-to-air heat pump. 

Everything RR says is true.

Just to complicate things further, some air conditioners have a resistive heating mode (as opposed to a heat pump heating mode) that turns them into a big fan heater. These can heat but only with a COP of 1, rather than the COP of 3 or 4 you might expect from an air-to-air heat pump.

Mostly these are portable units (portables with heat pump heating do exist but are pretty rare) but it's worth knowing about.

coffeehound

Reed_Richards said:

ASHPs can be air-to-air or air-to-water.  The former is more commonly known as air conditioning 

Perhaps more precise to say an air-to-air heatpump can operate as an air conditioner or can work in air-conditioning mode?

Reed_Richards said:

... but an air conditioner that uses a heat pump will be vastly more energy efficient than one that doesn't

The central difference between an air conditioner and a reversible air-to-air heatpump is that the latter contains a reversing valve to change the direction of refrigerant flow.  There is no separate 'heatpump' item; the collective system is the heatpump

Reed_Richards said:

So an air-to-air heat pump is an air conditioner but an air conditioner is not necessarily an air-to-air heat pump. 

Could be wrong, but I simply think of the ones that bring heat into the building, in whichever mode, to be 'heatpumps', and those that just operate in cooling mode to be air conditioners.  Reversable heatpumps can also work as air conditioners.  Not sure if there are different official definitions

matelodave

A heatpump is a device for moving heat from one place to another whether it's heat from outside to indoors or indoors to outside.

Likewise an air conditioner is a device for changing the conditions insdide the buildinh whether thats heating or cooling it (although when cooling it also has the added benefit of reducing the humidity as well)

Convention suggest that something that cools, is called an air conditioner and a heatpump is one that heats but in reallity they are the same - they just move heat around using a refrigerant and compressor.

Reed_Richards

It's silly to get bogged down by definitions or the lack of them.  The important thing is how much these units cost to run, which is dependent on their efficiency of operation.  With an air-to-air heat pump you might hope to achieve say 4 kWh of heat for 1 kWh of electricity or (I presume) remove 4 kWh of heat for every 1 kWh of electricity in air-conditioning mode.  If your air conditioner has heating elements for heating and acts like a wall-mounted fan heater then you will achieve 1 kWh of heat per 1 kWh of electricity.  What's important is not what you call the thing but how it functions.  

SuperHung

Reed_Richards said:

It's silly to get bogged down by definitions or the lack of them.  The important thing is how much these units cost to run, which is dependent on their efficiency of operation.  With an air-to-air heat pump you might hope to achieve say 4 kWh of heat for 1 kWh of electricity or (I presume) remove 4 kWh of heat for every 1 kWh of electricity in air-conditioning mode.  If your air conditioner has heating elements for heating and acts like a wall-mounted fan heater then you will achieve 1 kWh of heat per 1 kWh of electricity.  What's important is not what you call the thing but how it functions.  

I looked at the spec of my Aircon compressor. The COP for heating is 4.6, it uses R32 refrigerant.

danrv

The Toshiba has a COP of 4.09 for heating.

Gerry1

SuperHung said:

Reed_Richards said:

It's silly to get bogged down by definitions or the lack of them.  The important thing is how much these units cost to run, which is dependent on their efficiency of operation.  With an air-to-air heat pump you might hope to achieve say 4 kWh of heat for 1 kWh of electricity or (I presume) remove 4 kWh of heat for every 1 kWh of electricity in air-conditioning mode.  If your air conditioner has heating elements for heating and acts like a wall-mounted fan heater then you will achieve 1 kWh of heat per 1 kWh of electricity.  What's important is not what you call the thing but how it functions.  

I looked at the spec of my Aircon compressor. The COP for heating is 4.6, it uses R32 refrigerant.

danrv said:

The Toshiba has a COP of 4.09 for heating.

Does anybody ever achieve these values in practice?

They seem like the MPG figures that were bandied about for new cars.  They sounded impressive until you discovered that they related to a test car with the mirrors folded in, the driver was a jockey and the test was at steady 25mph in the desert at night with the lights and aircon switched off.

YMMV...

QrizB

I'm still curious as to SuperHung's relatively low price for a fully-installed split system. £3.3k seems quite reasonable for the system they describe.

@SuperHung who did you buy it from and would you recommend them?

Gerry1 said:

SuperHung said:

I looked at the spec of my Aircon compressor. The COP for heating is 4.6, it uses R32 refrigerant.

danrv said:

The Toshiba has a COP of 4.09 for heating.

Does anybody ever achieve these values in practice?

They seem like the MPG figures that were bandied about for new cars.

Well, they're measured under specified conditions and the supplier should tell you what those conditions are. Some suppliers even measure them under a range of conditions so you can eg. compare the COP when the outdoor temp is +5C to the COP at -10C.

matelodave

Gerry1 said:

SuperHung said:

Reed_Richards said:

It's silly to get bogged down by definitions or the lack of them.  The important thing is how much these units cost to run, which is dependent on their efficiency of operation.  With an air-to-air heat pump you might hope to achieve say 4 kWh of heat for 1 kWh of electricity or (I presume) remove 4 kWh of heat for every 1 kWh of electricity in air-conditioning mode.  If your air conditioner has heating elements for heating and acts like a wall-mounted fan heater then you will achieve 1 kWh of heat per 1 kWh of electricity.  What's important is not what you call the thing but how it functions.  

I looked at the spec of my Aircon compressor. The COP for heating is 4.6, it uses R32 refrigerant.

danrv said:

The Toshiba has a COP of 4.09 for heating.

Does anybody ever achieve these values in practice?

They seem like the MPG figures that were bandied about for new cars.  They sounded impressive until you discovered that they related to a test car with the mirrors folded in, the driver was a jockey and the test was at steady 25mph in the desert at night with the lights and aircon switched off.

YMMV...

Generally the COP figure is quoted at set temperature and flow temp for air-water systems - usually 7degrees ambient with a flow of 35 degrees. Many also quote at 0 degrees or 2 degrees ambient as well. However once you go outside these paramenter the COP will change, thats why ASHP performance is quoted as SCOP which is Seasonal Coefficient of Performance which tries to get an average.

However, it really is just like car MPG and the performance that you get in real life is dependant on how you use it rather that how it's tested in a factory