No, not at all. As you imply, you can’t create energy, only change it’s state. I didn’t put it very well I’ll admit.
I’ll leave you to do your own web search that will tell you much more than I’m prepared to write here but, essentially, the power you provide to the heat pump in order for it to compress calories contained in the air & return them to you as heat is around a third or a quarter of the returned heat.
The principal is like a fridge in reverse (unless you use it backwards for cooling your house, in which case it’s exactly like a fridge).
Put another way, 1kW of electrical power in provides round 3 or 4kW of heat back out - some claims are higher than that.
I am very pleased with my air heat pump system. So far its worked out a lot less expensive than previous old heating via convector heaters on timers and it blows further too depending on how high you set the fan.
It was that missing word ‘electrical’ that was causing me the problem. Sorry to seem overly pedantic but there are many folks who may form an erroneous impression of the facts if they are not presented in an exacting manner.
I like the honesty inherent in your statement of “some claims are higher than that”. To my thinking, that 1kW of electricity used to turn the fan is always going to push the same volume of air through the machine in any given time period. Therefore the amount of heat extracted from the air is going to vary depending upon the temperature of the air in the first place.
So would it not be the case that the claimed heat output should be stated with reference to the ambient outside air temperature at the time of the evaluation ?
As Badger expanded heat pumps do not create energy from nothing but merely move heat energy from place to place. They manage to do this against a thermal gradient which is neat - but not actually defiying physics. The clue is in the name - pumping heat energy around is exactly what they do.
Yes, they need electrical energy to move air and refrigerant around the system. Their total output is electrical energy in + heat extracted from source - conversion losses.
Heat extracted from source is normally the largest contributor making it appear that there is a “gain” over and above the electrical energy put in (which is the bit you have to pay for) - but overall there isn’t actually any thermal gain from the system.
Not at all. I consider myself the king of pedants, & hater of incorrect information.
Maybe, but it’s the compressor that determines the efficiency. The fan is simply there to pass air over the condenser fins.
Yes, it will. Modern systems can still work down into minus degrees C - yes, witchcraft!
I suspect one needs to read individual manufacturers specifications to get fully to the bottom of that one. Hopefully the COP rating is stated as an average.
“What, if any heating do you have in there at the moment Mike?”
I’ve been told that both have old oil-fired boilers, and there are large old-fashioned (and rather handsome) radiators in each room. There are a couple of blocked up fire places, the surrounds have been removed, so no nice fireplace features to retain, but might facilitate the installation of a back-up wood burner.
It doesn’t, well slightly as cold air is denser. The amount of heat depends on the volume of air, its density and the delta-T.
The difficulties lie in the fact that if you start out with air just above freezing it will have enough moisture to freeze on the heat exchanger which will drastically reduce its efficiency. This can be dealt with either by s separate heater or by reversing the flow of water and use heat from the system heat store to melt any build up.
Systems designed for very cold inputs - minus twenty to minus thirty don’t have this problem as the input air can’t hold a lot of moisture but they have a big hill to climb thermally to get useful output flow temperatures. There are two stage systems which can deal with either very low air temperatures, or achieve flow temperatures close to traditional boilers but that e have more losses so natively lower COPs.
Seems to me that for a heat pump to work well in very cold climates, it either has to be very sizeable, or of a more technically advanced / complex design to the average, and that in either case this is likely to substantially increase both the cost of purchasing the unit in the first place, and indeed of actually running it.
From the experiences of friends and neighbours that have this type of system, the general consensus of opinion is that they work reasonably well IF the air outside is not too cold, and IF the building is well insulated, and IF it’s only expected to provide background or baseline warmth.
From my ‘layman’s’ standpoint I reckon that such a heating system certainly needs a full professional evaluation before being embarked upon, as otherwise expectations will probably not be met, and a considerable amount of money could be wasted.
I think that different sorts of heating system are good for different types of building usage, and that very often this is not properly explained to the prospective purchaser beforehand.
Underfloor, or night storage heating gives a nice steady warmth once it has had time to get up to speed, so it is ideal for a permanently inhabited retirement dwelling, but pretty useless for a week-end ski lodge.
A matter of horses for courses with so many variables of different buildings, for differing usage patterns, in differing climatic conditions.
If the system is quite old you may have larger plumbing +22mm this is handy if you consider a heat pump. Old heat pumps (3 years +) are no match for the latest tech, with the change in refrigerents has come other benefits where heating flow temperatures can be up to 75c although lower flow temeratures are much more efficent but radiators need to be larger for cooler running systems around 45c.
Cold climate units can work to minus 25c but again at lower efficiency, back in 1985 I saw my first unit in Sweden and that could work to minus 15c warm climate units are often sold but look carefully at their design figures as they could well be poor at minus 5c.
The fans in modern inverter drive units are variable speed as are the compressors so are much more efficient than old single speed versions. Also fan noise can often be drastically less as the pump and fans modulate their speed the sound is less. I heard some very recently as low as 38db.
No Robert, modern inverter units modulate their speed on both fans and compressors to suit the ambient temperature and the heat demand. Refrigerents still boil at -25 so the system can still work if heat exchangers are sized correctly. Consider butane gas, no good outdoors in winter as it doesnt want to leave tank. Propane on the other hand has no problem and propane R290 refrigerent is where a lot of the new units out perform the older ones. They are fridges working in reverse. Fridge is cold inside with the heat lost out the back via the black radiator. Heat pumps draw available energy from outside and move it to the inside. Outdoor unit pushes out cold air.
I truly do not understand the machine which sits on the outside of the wall and somehow heats indoors.
This morning it was -8c outdoors. Would such a machine have given me warmth indoors and (if so) where would it have found it… ??
Don’t know but we have our bedroom reverse cycle air-conditioning and it was having a tantrum saying it was too cold until we realised that it was on AC not heater was toasty warm in minutes with no ‘too cold out’ message!!!
Without diving into tech talk, you often see frost on the outside of a gas bottle when a cooker is running. This is despite it being indoors. The change in pressure (reduction) causes that frost. Increasing the pressure would create heat. Thats what goes on inside the unit outdoors. The compressor pressurises the gas and it transfers the heat from outside to inside the pressure going up and down in the system as required. The gas is colder than -8 so it grabs the -8 to try and equalise the temperature. It doesnt grab as much in the cold weather but if designed it still works.
I am not techie, so to me the (very) cold air goes in to the pump, and even colder air comes out the exhaust pipe as it has sucked heat out. And the now warmer air goes into the house.
We have a hot water air source heat pump, and in summer unhook the exhaust vent and have a stream of cold air.
was toasty warm in minutes with no ‘too cold out’ message!!!