any Air Conditioning techs out there?

[Cuby2k]

Doug,
Do you know of a link that would show us (me) a picture and/or diagram of how a cap tube works? This is in-lieu of a TXV, is that correct?

Although I am fairly committed to the Earth Buried Copper (EBC) chilling method I would like to learn a bit more about this system.

 

[douggiestyle]

i can explain it.

a cap tube is just a small id tube. works like and orifice. do different than an valve other than it cannot be adjusted.

 

[cseeton]

I do not recommend capillary tubes for the DIY crowd for two reasons: because sizing them is more of an art than a science, and while the DIYer is making the fittings to connect to the titanium heat exchangers an inexperienced solder/braze job will plug it. A constant pressure valve or a TXV can be "tuned" by a curious DIYer and can lead to hours of entertainment/frustration.

I also don't recommend using copper pipe for your ground sourced cooling loop. It costs too much and the limiting factor is not the tube material - it is the thermal conductivity of the earth. Use PEX and save yourself time and money.

 

[douggiestyle]

agreed on the sizing thing. for efficiency and such it is an engineers nightmare or dream depending on therir pain thresh hold.

from an ease of building cap tube system is easy can use the old cap tube size. not much thinking needed. and as far as brazing the cap tube well that is easy. and there are adapters/fittings
that make it even easier.

 

[douggiestyle]

i may actually more difficult to convert an existing cap tube setup to one using a valve for the diyer. also adjusting the valve correctly will require some specialized tools. and error that could destroy the system.

 

[Cuby2k]

<a href=showthread.php?s=&postid=7352974#post7352974 target=_blank>Originally posted</a> by cseeton


I also don't recommend using copper pipe for your ground sourced cooling loop. It costs too much and the limiting factor is not the tube material - it is the thermal conductivity of the earth. Use PEX and save yourself time and money.

This really is the right forum for this discussion but sorry cseetron I could not disagree more on this point. The earth's relatively poor conductivity remains the same regardless of the tubing material.

As far as cost, compare using a refrigerant line set (using the 5/8" as an example) at 75 LF for a cost of maybe $70 vs a minimum of 1000' of PEX at $.31 /LF.

Where longevity is concerned, municipal water supplies have used copper service lines for 40 years+ without issue.

At the pressures that the copper will see in this type of loop and the thermal transfer that is required there isn't a better choice.

Please help me if there is something that I am missing.

 

[douggiestyle]

cuby here is the info you requested.

this gives some great advice. with this you can build your own chiller. it really is easy. this is not a large cooling system for an office building or such. this is basicly a $300 top mount frig.

use this comparison. a lawnmower engine vs nascar engine. yes they are both engines. and i can repair my lawnmower. but they would shoot me before they would let me put my hands on dale jr's engine. their is no comparison.

http://fridgedoctor.com/fridge-doctor-book/capillary-tube.html

i like this one better

http://fridgedoctor.com/fridge-doctor-book/installing-a-new-compressor.html

this site only allows you to vist it a few times. then it tries to sell you a book.
if that happens you will have to delete your cookies.

 

[Cuby2k]

Cool, (pun), thanks Doug.

 

[douggiestyle]

also if you were replacing the cap tube its not that difficult to size or resize depending on length. like a remote compressor condensor.

http://www.supco.com/images/20 cap tubing.pdf

no offense to the hvac techs out there. but they aint sending an engineer to fix my frig or replace my air conditioner

i have a MUCH better table its a pdf. if anybody wants it just pm me your email and i will send.

 

[cseeton]

I am in no way saying that you can not use copper, I jsut don't recommend it because it costs too much and every solder connection you have in the ground better be a good one. If you can get 5/8 copper coil 75ft for $70, that is a good price, the cheapest I have found recently for a 50ft coil is $150.

You nailed the reason to use PEX in two statements:

The earth's relatively poor conductivity remains the same regardless of the tubing material.

minimum of 1000' of PEX at $.31 /LF

The low conductivity of the earth means that you can use just about any tubing you want because you will not be able to push heat into the soil faster than the soil will accept. PEX or copper behave the same with surronded by an excellent insulator - good ol' mother earth.

You will need much more that 75 feet of tubing to reject any appriciable amount of heat; 200-500 ft would be a better starting point.

 

[douggiestyle]

<a href=showthread.php?s=&postid=7353960#post7353960 target=_blank>Originally posted</a> by cseeton
I am in no way saying that you can not use copper, I jsut don't recommend it because it costs too much and every solder connection you have in the ground better be a good one. If you can get 5/8 copper coil 75ft for $70, that is a good price, the cheapest I have found recently for a 50ft coil is $150.

You nailed the reason to use PEX in two statements:





The low conductivity of the earth means that you can use just about any tubing you want because you will not be able to push heat into the soil faster than the soil will accept. PEX or copper behave the same with surronded by an excellent insulator - good ol' mother earth.

You will need much more that 75 feet of tubing to reject any appriciable amount of heat; 200-500 ft would be a better starting point.

could you not hijack this thread and take this to the geo chiller thread. Thanks

http://www.reefcentral.com/forums/showthread.php?s=&threadid=817756

 

[Drake1]

so now we are on the cap verse valve...the vending tech guy is worried about getting the right length on the cap tube since he has no reference and also the difference sizes in the cooling lines, if i remember right the condenser has a 3/8 or 1/2 line and the exchanger has a 3/4 line so doesn't it have to use a valve when your changing line size?

 

[cseeton]

No, you don't have to use a valve to change sizes; you can use reducing fittings and braze them together. As far as cap tube length, a good estimate is on the back of the cap. tube box, just match the length to the condensing unit capacity. Tell the tech that there will not be a measurable superheat since the heat exchanger is much larger than the condensing unit capacity, install a sightglass on the high side before the cap tube and charge to the point where the flow is full liquid with an evaporating pressure corresponding to 40F.

Best of luck!

 

[AcroSteve]

I used the cap tube that came on the window mount AC unit I used for my chiller. Even though it is not a sophisticated as a TXV, I have not had any issues.

 

[Karl K]

If you have not completed the project yet, I would recommend using the TX valve (it appears that is what you have). You don't really have to adjust the valve. You just have to place the sensing bulb on the right place on the suction line (right after the evaporator)

For refrigerant, I would recommend using R-134a as you can buy it at Fred meyers or some similar shop in the states. It's not as easy to get it up here in Canada.

Please e-mail me. I am very interested to see what your finished project looks like. If you are not done, I could point you in the right direction with any problems you may have.

 

[BeanAnimal]

you mean they still allow ANY refigerant up there

 

[Karl K]

Well, it is already pretty cold up here. We can just leave meat out for days on our countertops (being made of ice) and it won't go bad.

Strangely enough, we still want it colder at some times.

Go figure...........