Newbie question regarding expansion valve

[theoldwizard1]

I understand the basic heat pump cycle and all of the components in the system (compressor, condenser, expansion valve, evaporator). I also understand how the basic cycle can be "turned around" (the evaporator turned into the condenser and vice versa) with some valves. My question has to do with the expansion valve.

Where, in a heat pump system, is the expansion valve and capillary tube placed relative to the various valves and other system components ?

Pictures and diagrams would be helpful.

[theoldwizard1]

Originally Posted by theoldwizard1

Pictures and diagrams would be helpful.

More Googling and this is what I came up with

[jeff5may]

From yhe sticky:

Basic cycle


geo heat pump

[theoldwizard1]

Originally Posted by jeff5may

From the sticky:

The problem with those diagrams is that they only show the heat pump working in one direction. I knew there had to be some trick with the TXV for the heat pump to work in both directions, like the fact that there are 2 in my diagram, paralleled by one way check valves.

I am certain that there is "more than one way to skin the cat", but the solution I found looks pretty simple.

[theoldwizard1]

Yet some more images

[jeff5may]

The two expansion valves in the diagram can be switched out for a single cap tube or electronic expansion valve. The way of the diagram is the way of the old school split system. The idea behind the rig is you can swap either side of the unit with out the other. The check valves shunting the expansion valves are not there in a straight ac split unit.

[theoldwizard1]

Originally Posted by jeff5may

The way of the diagram is the way of the old school split system.

Maybe, but it makes it simple and makes the system easy to understand for newbies !

The two expansion valves in the diagram can be switched out for a single cap tube or electronic expansion valve.

I figured an electronically controlled valve would be a likely replacement. I assume that with an EXV a one way valve is not required (cost savings) because the valve can be opened far enough to NOT cause (very much) restriction for high pressure liquid going to the other EXV. Another cost save is the elimination of the equalizer port and associated piping.

Can you find a diagram showing only 1 TXV/EXV ?

[NiHaoMike]

In theory, it's possible to make a TXV that will work both ways. In practice, I don't know of any TXVs that are designed to work both ways.

That said, TXVs are cheap on the surplus market.

[theoldwizard1]

Originally Posted by NiHaoMike

That said, TXVs are cheap on the surplus market.

That is what I thought ! Under $25 on eBay. For DIYers 2 TXV and 2 one way valve is a very simple solution.

[jeff5may]

Originally Posted by theoldwizard1

Maybe, but it makes it simple and makes the system easy to understand for newbies !


I figured an electronically controlled valve would be a likely replacement. I assume that with an EXV a one way valve is not required (cost savings) because the valve can be opened far enough to NOT cause (very much) restriction for high pressure liquid going to the other EXV. Another cost save is the elimination of the equalizer port and associated piping.

Can you find a diagram showing only 1 TXV/EXV ?

https://www.google.com/url?sa=t&sour...ymGGQeF_Tpgwsg