Cheap heating

[Andrew Gabriel]

Not as efficient as a compressor heat pump. And neither are Peltier effect heat pumps.

[Fred]

I'm not familiar with methods of running an air source heat exchanger at very low temperatures without the problem of icing. Any icing would rapidly reduce efficiency to 100%.

Another reason for poor low temperature working is like to be from the choice of refrigerant.

[Doctor Drivel]

If you are using heat that normally would be wasted, they are very efficient in running costs.

[Doctor Drivel]

In a humid climate the icing problems are more pronounced.

[John Rumm]

As dribble says, that would be the cost of "only running a small pump"...

So compared to the 200 quid heatpump aircon, all you need is a couple of grands worth of panels and their installation, say a grand and a half for the thermal store setup and control logic, and a grand to retrofit UFH in the conservatory.

But then he has a unique ability to see "value" in situations that pass us mere mortals by! ;-)

[Rob Morley]

Or use a pump to make the inside cooler and the outside warmer - when the inside gets so cold that the pump can no longer extract heat to the outside then you have used up the source of heat.

[Doctor Drivel]

This thick pillock is at it again. Some mothers.....

This a/c unit gives out under 4 kW - wow that will heat your house. A full solar system costs just the pumps to run and will heat the whole house and most of the DHW.

[jacob]

A gas fridge is a heat operated heat pump

The output of the heat pumps is not

Yebbut an aircon unit is not simply moving hot air to a cooler place (a fan would do that) - it's moving heat 'uphill' from cold air outside to a warm interior - following your water analogy it is extracting the heat FROM the COLD tank and transferring it to the HOT without moving any water at all - at least that is what seems to be said in this thread - and somehow this is more efficient than directly heating the hot tank with say an immersion heater (100% efficient already?)

Jacob

[Russell Eberhardt]

Sorry, I was forgetting. Here, on the edge of the Pyrenees, there is a lot of hydro-electric and wind power used. Most of the balance is generated in nuclear power stations. Very little fossil fuel is used.

Russell.

[Russell Eberhardt]

If tou can't answer with logic, resort to abuse!

No, 4 kW will not heat my house but it is installed in my living/dining area and provides sufficient heating for most of the winter and useful background heating when it is really cold and I light the log fire.

I wasn't asking about the running costs but the purchase and installation costs for solar heating.

Russell.

[Russell Eberhardt]

I am only quoting from the manufacturer's specs. I beleive the outdoor unit has an automatic defrost cycle. How well it works in really cold weather I will have to wait until February to find out. I have however spoken to a number of people who have installed units and found considerable savings on electricity.

Russell.

[John Rumm]

You need to dissasociate "heat" and "temperature" in your mind - they are two differnt things; not unlike flow rate and pressure, or voltage and current.

A spark from an angle grinder may be over 1000 deg C - it has a very high temperature - but little "heat" or energy. A bath full of water at

40 deg C has loads of heat but a low temperature.

Heat will naturally flow from higher temp objects to lower temp ones (it will also flow in the other direction - but the nett effect is high to low). If you add a "pump" however it is possible to reverse that nett flow direction. So you are pumping "free" heat out of the cold thing and putting it into the warmer thing. So the outside gets colder and the inside gets warmer.

Running pumps however is not free - you need to put energy in. In this case however that is not a bad thing since we can arrange for the energy that is put to be dissapated in the room; adding to the heat we are pumping in.

So you use say 1kW to pump 3kW of heat from A to B, and then arrange for the waste heat produced by the input of 1kW to also end up in B.

(The same happens in the summer when you run it in air con mode - for every 3kW you extract from the room, you end up throwing 4kW outside)

[John Rumm]

Alas real world practicalities and costs never enter into dribble's half arsed schemes...

The capital costs of solar are going to be higher than a conventional system, given that they will typically be in addition to a conventional system. They are also higher still to retrofit, than to build in in the first place. If you already had a thermal store system and UFH, then the picture would be different - you may be able to recoup the capital costs reasonbly quickly from the energy savings.

[Steve Firth]

Plenty available if you leave the Uk and look for them. Castorama (B&Q under a diufferent name) sells them at very good prices - as low as EUR

190 for a 1300 watt model.

[Dave Plowman (News)]

The problem with this is that water is everywhere, and when it freezes ice is a good insulator, preventing transfer of 'heat' to the exchanger.

[Doctor Drivel]

Pillock brain is at it again. Detached from reality.

[Doctor Drivel]

What abuse? The man is obviously thick and a pest. He is also from Essex.

Yet cost more to run that a full solar system using low temp UFH.

[Doctor Drivel]

They would do, over electric resistance heating. In the UK over natural gas, no. The most efficent tumble dryers use heat pumps.

[jacob]

Aha! - I think I've got it - the external air temp being higher than that of the refrigerant in it's cold phase will heat it up and so reduce the load on the compressor for a given temp of refrigerant on the hot side. So reversible (reversed) air conditioning not v effective due to heat exchange via air (poor conductor) which in winter will be cold (and sometimes colder than the refrigerant?), whereas ground source heat likely to be higher temp and more stable - hence all emphasis on the sites I've looked at is on ground source heat. Is the point of reversible electric air conditioning more to do with the fact that it is already installed and will perform both functions, rather than any substantial energy saving? Thanks for patient attempts at explanations - I always think that if you can't explain it then you don't understand it!

cheers

Jacob

[Andrew Gabriel]

I did a price comparison between here and the US about 18 months ago -- US was around 1/3rd the price for same power transfer. I recall a Usenet posting where someone bought one in the US and carried it back as baggage.