AC is a heatpump. pumping heat from inside to outside. “Heatpump” is also a heatpump. pumping from outside in. The only difference is fluid flow direction.
Hence only thing needed to turn one to other is 4 way valve changing the flow direction/order of refrigerant.
These days atleast in Europe, good luck finding “heat pump”, that doesn’t have 4 way selector valve. Early on there was single direction heat pumps and cooling was extra feature only on upmarket models. These days it is “oh right it also has cooling, handy”. The valve is not that expensive, so it is pretty standard by now.
Not sure if I get it entirely.
With classical heatpump (and by this I mean the one for heating) the external unit expands the refrigerant, so it absorbs the heat from air. If it was used for AC, then it should compress it instead.
But if I understand properly (doubt) 4 way valve, I would require an unit that either compress it outside or expands it inside.
No, it only needs to do one and you flow it in reverse.
The pump compresses the gas, this increases its temperature, but maintains it as a gas.
The liquid goes by a coil and a fan blows on it.
The air blowing on there transfers heat from the gas to the air.
The air blown by this fan is hot, as it contains the heat that was removed from the gas.
Due to the temperature drop the gas condenses into a liquid.
The liquid goes by a one way valve where it’s allowed to expand, this decreases the temperature but it remains a liquid.
The liquid goes by a coil, similar to the other one, but this time the fan transfers heat from the air into the liquid and converts it back into a gas while blowing cold air.
Now if you think of this as 3 different pieces, a central one with the pump and expansion valve, and two coils it’s easy to understand that if you just connect the coils in reverse the one that was heating now cools and vice versa. So all you need is to have the central piece be connected to a valve that allows it to switch which coils connect to which side and you’re done.
4 way valve is 4 way exactly so the compressor can essentially switch sides on the cycle. It also shifts around where the expansion valve is located in cycle. thus switching the tasks of the inside and outside radiators/heatexchangers.
A heatpump to heat the home (which is commonly referred to as a heatpump) and a heatpump to cool the home (which is commonly referred to as airconditioning) are effectively the same thing but run in reverse.
All a heatpump does is move heat from one place to another. For heating you move heat from the outside to the inside, and for cooling you move it in reverse.
Airconditioners (which are just heatpumps) often have a valve which allow you to reverse the flow. That is why most air conditioners can be used for both heating and cooling without the need for any significant amount of extra hardware.
As a bonus, because a heatpump moves heat rather than generating heat, they heat the home by 4-6 kWh of heat energy for 1 kWh of electricity they consume. (This ratio is the referred to as the COP-value, and you can look it up for all ACs. They usually list separate COP values for heating and cooling)
This makes them significantly cheaper to run than gas boilers, even if gas is significantly cheaper per kWh than electricity is.
That’s basically two units in one or how does it work?
AC is a heatpump. pumping heat from inside to outside. “Heatpump” is also a heatpump. pumping from outside in. The only difference is fluid flow direction.
Hence only thing needed to turn one to other is 4 way valve changing the flow direction/order of refrigerant.
These days atleast in Europe, good luck finding “heat pump”, that doesn’t have 4 way selector valve. Early on there was single direction heat pumps and cooling was extra feature only on upmarket models. These days it is “oh right it also has cooling, handy”. The valve is not that expensive, so it is pretty standard by now.
And modern AC’s can heat as well.
Not sure if I get it entirely. With classical heatpump (and by this I mean the one for heating) the external unit expands the refrigerant, so it absorbs the heat from air. If it was used for AC, then it should compress it instead. But if I understand properly (doubt) 4 way valve, I would require an unit that either compress it outside or expands it inside.
No, it only needs to do one and you flow it in reverse.
The pump compresses the gas, this increases its temperature, but maintains it as a gas. The liquid goes by a coil and a fan blows on it. The air blowing on there transfers heat from the gas to the air. The air blown by this fan is hot, as it contains the heat that was removed from the gas. Due to the temperature drop the gas condenses into a liquid. The liquid goes by a one way valve where it’s allowed to expand, this decreases the temperature but it remains a liquid. The liquid goes by a coil, similar to the other one, but this time the fan transfers heat from the air into the liquid and converts it back into a gas while blowing cold air.
Now if you think of this as 3 different pieces, a central one with the pump and expansion valve, and two coils it’s easy to understand that if you just connect the coils in reverse the one that was heating now cools and vice versa. So all you need is to have the central piece be connected to a valve that allows it to switch which coils connect to which side and you’re done.
4 way valve is 4 way exactly so the compressor can essentially switch sides on the cycle. It also shifts around where the expansion valve is located in cycle. thus switching the tasks of the inside and outside radiators/heatexchangers.
A heatpump to heat the home (which is commonly referred to as a heatpump) and a heatpump to cool the home (which is commonly referred to as airconditioning) are effectively the same thing but run in reverse.
All a heatpump does is move heat from one place to another. For heating you move heat from the outside to the inside, and for cooling you move it in reverse.
Airconditioners (which are just heatpumps) often have a valve which allow you to reverse the flow. That is why most air conditioners can be used for both heating and cooling without the need for any significant amount of extra hardware.
As a bonus, because a heatpump moves heat rather than generating heat, they heat the home by 4-6 kWh of heat energy for 1 kWh of electricity they consume. (This ratio is the referred to as the COP-value, and you can look it up for all ACs. They usually list separate COP values for heating and cooling)
This makes them significantly cheaper to run than gas boilers, even if gas is significantly cheaper per kWh than electricity is.