Anyone ever try a precision needle valve?

[Flybye]

Hi guys :D I'll try not to act too much like a newbie ;)

Anyways, has anyone ever considered using a precision needle valve in place of the cap or expansion valve?

I was thinking....the purpose of the cap tube is to allow enough pressure to build up in the high side, and the more restriction, the lower the low side may be able to give off colder temps. In my own little crack head world, a precision needle valve [i]should[/b] be able to do the exact same thing. While also giving you the added benefit of flexability.

I've read of people readjusting their expansion valves, but I've also read of expansion valves being too big for certain applications. All I have is a 1/5hp R134 compressor. It's a small refrigeration unit I got off of Ebay. It originaly came with an evaporator block used to cool down a laser diode, but I replaced it with a spherical heat exchanger. I've been able to get as low as -02F/-19C with the cap tube it came with. I didn't bother replacing the cap tube because I have no clue as to how to calculate it.

The small sledge hammer was just in case the unit didn't work right ;)

http://www.xtremesystems.org/forums/attachment.php?attachmentid=17322&stc=1

[saaya]

hey Flybye :toast: welcome to XtremeSystems :)

unfortunately i dont know anything about that stuff ^^ hhaha

you should post in the phase change section, they should be able to help you :D

[Flybye]

Ok...
I guess this was a dumb idea :p:

Yeah, I posted a linkie over there :)

[unixxx]

The professional equivalent to this idea is a TEV/TXV (hope that's the right acronym) which is basically an electrically adjusted valve that automatically adjusts based on the refrigerant temps. I'm sure you could wire this to be manually adjusted.

[chilly1]

I use a PEV on chillers, this allows you to set the pressure ant it will hold it there. The PEV has a needle valve attacked to a pressure regulating device.

[i_jester]

I took the low-tech approach to controlling the temps on my chiller, since I had no access to AC technicians or supplies.

I bought an industrial cooling bulb thermostat with a adjustable temperature differential from Grainger for $39. It turns on a relay when the coolant temp gets above the set point, and turns it off below. The temp differential lets you adjust the difference between the two so it doesn't turn on and off at the same time.

I figure it is harder on the compressor to cycle it like that, but I wasn't looking for a 20 year project.

[Flybye]

.....I figure it is harder on the compressor to cycle it like that, but I wasn't looking for a 20 year project.
But what's harder on the compressor?
To leave it on 24/7 or have it cycling?

[chilly1]

Cycling is harder on the compressor. With a properly sized and charged system with a PEV you can dial it in and forget it.

[i_jester]

But my way is much, much cheaper and easier for the average joe.

AC Unit - $69.95
Reservoir - $20
Thermostat (-30 to 90) - $39.95