Heat Pumps and Electric Heating - why the TXV? (thermostatic expansion valve)

as far as i can tell, it cuts flow to the ah coil when it gets cold? How is this progress? How well will it dehumidify? Sounds like a bad idea for my double size hp.
Now im going to forget the r410a with its' 24-36% higher amp draw(global warming due to burning more coal to run higher pressure, and higher electric bills) and txv!
i'm sticking with r22 unless u guys can better inform me on this.

You are asking basic refrigeration questions. I suggest that rather than asking several basic questions on this forum that you instead visit your public library and check out a few books on refrigeration.

Modern Refrigeration and Air Conditioning by Andrew D. Althouse and Carl H. Turnquist is a good overview of how systems work and the function of the individual components. I am sure that there are many other good introductory texts you can check out.

thanks to you guys i now know enough to ask the right questions.
i will have to defer to the installer; present my situation, ask for his best effort. rely on his experience, and his warranty.
i would need to attend a workshop to see demonstrations of various changes. I wish i had that book, but, i already spent 4 weeks on this, and it's time to buy. For my next system i will 1st buy the latest book. i had no idea how complex it is; now i know; i'll be ready next time.

Basic refrigeration cycle is pretty easy, it is the refinements that make the study of it difficult.

A Thermal Expansion Valve (TXV) is an upgrade over what was (and still is) common on on both home refrigerators and home air conditioners. Most use a device called a capillary tube to meter the liquid refrigerant to the evaporator (cooling) coil.

The problem with the capillary tube is that it is a "set load" device and works optimally only under specific design criteria. When the conditions, such as cooling load or condenser temperature changes the capillary tube then is either too small or too large to properly meter the liquid refrigerant. Capillary tube systems are also extremely fussy when it comes to the total amount of refrigerant in the system.

A TXV, however is able to change the amount of refrigerant it meters under changing conditions. It is less finicky when it comes to the amount of refrigerant in the system. Of course the trade off is that it is also more difficult to do the manual adjustments (a capillary tube has no manual adjustment) to properly "tune" it to the system and, of course, it is a far more expensive device than a capillary tube.


The same is true of most of the components of a refrigeration system. It is fairly easy to design a brute force system but it will have a high price tag and probably require frequent adjustments for optimal performance. The devil is in the details and to design and install an air conditioning or heat pump system that works at maximum performance and minimal cost is quite the balancing act.

Matt Gruber Might go here and check out the R22 bull.

http://www.toad.net/~jsmeenen/freon.html

We put more chlorine in the air just from the swimming pools down there in FL that from any R22 ;)

furd
i plan to ask him how to adjust the txv, if necessary, rather than call him.(thanks to your explanation)
.
my ruud instructions describe a "piston" size 67 or 70. is this a fancy term for an orifice? or does it move up & down and vary flow?

Thanks!

It has been close to thirty years since I worked on any refrigeration equipment. I never worked on any residential systems, only commercial water chillers and the smallest was rated at fifty tons.

You cannot adjust the TXV as it requires gauges connected to the pressure parts of the system and electronic thermometers.

All pressure parts of refrigeration systems are off limits to anyone that has not been trained and passed a test, then issued a permit for such work by the US Environmental Protection Agency.

Refrigeration work is fascinating but unfortunately it just isn't a place where a DIYer can do much.

Sorry.

Most of the TXV for the home coils are fixed and you cant adjust them at all. Not even change the head on it out.

thanks to you guys i now know enough to ask the right questions.
i will have to defer to the installer; present my situation, ask for his best effort. rely on his experience, and his warranty.
i would need to attend a workshop to see demonstrations of various changes. I wish i had that book, but, i already spent 4 weeks on this, and it's time to buy. For my next system i will 1st buy the latest book. i had no idea how complex it is; now i know; i'll be ready next time.

Matt you are a great sales man to get a company to warranty a unit that is twice the size it should be. Do you sale used cars?

Moderator note:

This thread serves no useful purpose.

i plan to ask him how to adjust the txv, if necessary, rather than call him.


It is not permitted to work on a/c systems without being certified and this site does not support the offering of advice to work on this equipment.

Thread closed.