Air to Air Heat Pump

[bugsyuk]

Can someone please explain to me (in simpleton terms) what is the difference between an air to air heat pump and air conditioning.I know that the heat pump take s the air from outside of the property and recycles it as hot air inside. Apart from that surely the two systems are virtually the same thing. Waits to get shot down in flames for this question.:63:

 

[jason121]

Air to air is air conditioning. Works via the vapour compression cycle just like your fridge.

 

[Worcester]

The difference is that one is orientated to condition it hot, the other cold. Most Air-Air Heat pumps will work in reverse, i.e cool in summer. Additionally they are usuallly installed in different places as to where you want to heat / cool, so one is optimised to extract heat from outside (even when cold) and pump controlled heat inside, where as the other is optimised to cool hot air in a controlled way ad dump heat as efficiently as possible.

The underlying technology is the same - however you don't drive your car at 70mph in reverse (or do you ) for example the steering is at the wrong end

Principle the same, detailed design, engineering and installation loccation different.

 

[plugsandsparks]

I install these little gems. Heat pump has now become a generic term for the unit that sits outside. Nowadays these units can cool one room, heat another and provide hot water at the same time.
Air conditioning is like a subset of what a heat pump can do.
Air to air simply means it sucks in air and blows out air to grab the latent energy from the air.

 

[Worcester]

@plugsandsparks, given that air-water heat pumps don't seem to offer a brilliant return through the RHI, we are simply looking at what's best for cutsomers.

Out of interest whose units that have all the capabilities that you mention do you install?

Thx.

 

[jason121]

@plugsandsparks, given that air-water heat pumps don't seem to offer a brilliant return through the RHI, we are simply looking at what's best for cutsomers.

Out of interest whose units that have all the capabilities that you mention do you install?

Thx.

Disagree with you on that one, Savings around £300 compared to oil RHI payments to cover most of the install, Gas prices to rise 8 % this year. No brainer for. My gas bill this quarter 68 pence, no worry of carbon monoxide poisoning.

 

[plugsandsparks]

Have to say i was confused when i started looking at the manufacturers data, but i can see that they will consume 1Kw and give out about 3.5KW but it is an expensive way of doing it so payback is long.
Very recent example was heating a warehouse using 84kw of heat pump, it beat LPG and oil quite easily and i was going with that solution until we enquired with National Grid and found Natural gas was doable. As i am Fgas but not Gas safe i have taken on the PM role to get the job done because basically for the price of one heat pump solution for one warehouse we can get two warehouses on natural gas for the same price over a 4 year period with heat pump over taking after year 5.
I am not in the renewables market - i do air source heat pump solutions for businesses. i,e . heating and cooling of offices and the like as an alternative to a central heating solution or in the above case warehouse blown air heating using fossel fuels.

There are a few VRV systems on the market that will do what i was describing but they are not cheap,
Have a look at Daikin VRV Systems | Reducing energy waste and CO2 emissions | Daikin
cheers

 

[Worcester]

@jason121, on a straightforward retrofit, when you add in the cost of upgrading the rads, its is a very close call.

If the house is well insulated, that makes a big difference, most of my customers are rural detached 4-5 bed running on oil, cavities filled and lofts insulated.

We find a big discrepancy between estimated consumption (kWh) from MCS and the EPC. We find that the MCS calc is usually pretty close to actual bills also.

As the RHI is paid based on emmitter star rating, and then only for the renewable element (rightly so) at 45° flow temp , an ASHP is rated at an SPF of 3 (and you need to oversize the rads by a factor of 3.1 based on a Δt50) with your SPF of 3 you'll only get paid for 2/3 of the heat, and when that figure is already about 30% out, means you only get paid for half of the ACTUAL heat required ...

EVEN adding in fuel saving, sometimes it just doesn't add up...

 

[jason121]

We run radiators at 50 degree. Which calculation to use to size heat load of building. I didn't think the new figures were set in stone yet. Most of our customers have been given grants to install heat pumps of around £4500. Which helps a lot.

 

[Worcester]

SPF figures in stone since February last year (2012) ... @50° you'll be at an SPF of 2.7, however it's not what you've set them at, it's what the radiator capacity is that actually matters, so if the calcs say 55° that is what it will be., else they can accept a gov't decreed SPF of 2.5.

Remember also that if the grant has any public money attached to it, it will be clawed back against the RHI - they have made sure they don't pay twice.

 

[jason121]

SPF figures in stone since February last year (2012) ... @50° you'll be at an SPF of 2.7, however it's not what you've set them at, it's what the radiator capacity is that actually matters, so if the calcs say 55° that is what it will be., else they can accept a gov't decreed SPF of 2.5.

.

Don't understand the above, I have software that when entering existing Radiator size works out new radiator to 50 degree or not if the radiator is suitable sized to the room.

 

[Worcester]

@jason121 (this is a bit off topic for air-air so really we should have started a new thread perhaps we should even move it to the plumbers forum )

I have software that when entering existing Radiator size works out new radiator to 50 degree or not if the radiator is suitable sized to the room.

Yeah, but you know MCS (think shading :coolgleamA if it doesn't match the MCS emmiiter guide how do you justify it and what star rating do you give it?

Out of interest which softare package is it? And I'll do a quick check against the guilde ..

 

[Worcester]

@jason121, I've run that software , and yep it uses the formulae in the MCS emitter guide and also does the room and building heat demand / loss calcs properly - someone put a lot of time putting that together - well found !

So long as any radiator changes that are recommended are done, that's a fairly straightforward tool that makes life easy, and with inputs for 24 rooms it should fit most domestic installations

Having had more than few so called pl****rs work for me, their ideas of boiler and radiator sizing, aka heat loss calcs, leave me worried about how many systems have been installed wrongly, hence my earlier comments, also why when running at 50° often radiator changes aren't always needed.

Thanks for the input.