Why the expansion valve is in the outdoor unit in split a/c?

[pathum619]

Im more curious about having the expansion valve in the outdoor unit in split a/c?
It is more effiecient if it was on the indoor unit. (more subcooling and no vapourization of liquid in the luid line due to bad insulations)
Can any one tell me the genuine reason?
My opinion is that the static pressure drops in the vertical piping may result in flash gas and beacause of that they did this. Is it correct???

[chemi-cool]

It is a capillary tube so all the pipes and inside unit are low pressure.

Ac units, window and split were made at first to cool only and heating mode came much later so I guesss this is why.

[The Viking]

Also the balance of the liquid volume, in cooling mode all the liquid is contained in the outdoor unit so less is needed and in heating mode excess liquid is stored in the interconnecting pipe.

And, if the EEVs were in the indoor unit you would still have the smaller interconnecting pipe after the EEV when the unit goes in to heating. Look at various makes of VRV/VRF, they got the EEVs in the indoor units or BS/BC boxes, then they need additional EEVs in the outdoor units and also expansion vessels.

:cool:

[Copperteck]

I was always told it was to reduce the noise made by the expansion device. If it was in the indoor unit it would be much louder!

[Rob White]

.

Two reasons in my opinion

One is noise. Customers don't like the hissing sound
some expansion devices can make.

The other is ease of installation, who do you think
installs the most AC units? People who are semi skilled
or possess little or no skill. Imagine the Far East, Middle
East, Asia and all the other warm places where the majority
of AC units are sold and installed by people with little skill
and no tools..

Rob

.

[Peter_1]

Chemi, it's at least 10 years now we could find unis with capillary tube. All have EEV's now.
Noise was the main reason, then like The Viking said

[pathum619]

Thank u guys & engineers...

[tmm]

Fitting the expansion point on the outdoor unit enables the overall piping length to be increased from a system which contains the expansion point within the indoor unit. The use of capillary expansion enables the system to balance and thereby reduce the starting load on the compressor.

tmm

[NiHaoMike]

Pretty much all the R22 and R410a units in the US have the TXV as part of the evaporator coil.

[The MG Pony]

same here in Canada, or a piston orifice, never onces have I seen an EEV on a unit, and never the expansion device on the condenser side, mind you whole house splits are the most prevalent second only to window shakers

[NiHaoMike]

same here in Canada, or a piston orifice, never onces have I seen an EEV on a unit, and never the expansion device on the condenser side, mind you whole house splits are the most prevalent second only to window shakers
Heat pumps do have a second TXV or capillary tube in the outdoor unit, but to be pedantic, when that is active, the outdoor coil is the evaporator.

[The MG Pony]

yup, built a few capilery heat pumps for fun, but notice I did say air cons ;) thats about the only time we really see any thing in the out side unit!