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.
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.