Remote vs close coupled systems

[Gary Lloyd]

It occurs to me that many in this forum may have the impression that the refrigeration system must be sitting next to the computer. Not true.

The liquid and suction lines can be any length you want, placing the condensing unit in the next room, the other end of the house, in the basement, in the attic, indoors or outdoors, anywhere you like. Of course, all of these add complexity to the system (and lots of insulation), but it can be done.

[berkut]

Unfourtenetly thats very hard to do in some conditions.. like my house- i have 0.5m walls, ceelings etc... and new windows so i cant drill through them :\

[Holst]

What about taking lines above and below the compressor...

As far as ive under/mis-understood... this can have an effect on performance and on where the oil goes.

Would you mind explaining some of these complications...

I think my own system will need to be portable, so it makes sense to keep the lines short, but its an interesting idea...

[Gary Lloyd]

Unfourtenetly thats very hard to do in some conditions.. like my house- i have 0.5m walls, ceelings etc... and new windows so i cant drill through them :\



You live in a bomb shelter?

[berkut]

No, most of Polish houses are made like that...

[Szymek]

Originally posted by Gary Lloyd
You live in a bomb shelter?

ROTFL really LOL

:toast:

At least our houses are not going to be taken by tornado :banana:

HEAVY DUTY

[Gary Lloyd]

What about taking lines above and below the compressor...

As far as ive under/mis-understood... this can have an effect on performance and on where the oil goes.

Would you mind explaining some of these complications...


Hmmmmm... Where to start?...

Long lines, and the liquid line in particular, adds to the total amount of refrigerant in the system. We can minimize this by using as small diameter line as possible, but keeping in mind that we do not want to restrict the flow.

When the compressor is shut off, the evaporator is the coldest part of the system, therefore liquid refrigerant will accumulate in it. If the suction line is downhill from the evaporator, gravity will carry liquid to the compressor inlet, flooding the compressor on startup. The more total refrigerant in the system, the more likely the flooding.

We can counter this by having the suction line go above the evaporator before going down to the compressor, thus trapping the liquid in the evaporator, or by trapping the liquid somewhere in the suction line. That's what the dip in the prommie suction line is all about.

Another strategy would be to install a solenoid valve in the liquid line near the metering device (cap tube, TEV) inlet, which would close when the compressor shuts off, stopping the flow to the evaporator.

Then there are oil return problems. We can make oil go uphill by increasing the velocity of the vapor, again keeping in mind that we do not want to restrict the flow. Like placing your thumb over the end of a garden hose to increase the velocity of the water, we can decrease the inside diameter of the suction line to make the vapor blast the oil up the suction line.

If you have sat in your car through an auto-wash, you may have noticed when the air drier comes on, the water crawls up the windshield. The oil crawls up the inner walls of the suction line in much the same way.

There is more to it, but that's a good start. :D

[berkut]

Gary - remember about increased load on the system. Usually we have small systems, we want minimal temps and the loads are small. The increased load would "kill" some small systems performance

[Gary Lloyd]

I agree, Berkut. Heavy suction line insulation is needed.

As always, insulation is our friend. :D

[DaBit]

Most people want to keep the refrigeration system and PC coupled, hence the grouping of the two.

If I intend to move the PC a few meters from the refrigeration system, I would use a chiller. Less refrigerant needed, less pressure drop, less oil problems, and easier to route the hoses, relocate the unit, and separate the PC and cooling (e.g. for transport).

[Gary Lloyd]

I am not advocating remote systems. I am simply pointing out the fact that there are options. :D

[bowman1964]

gary great idea....since mine is remote....LOL.my triple is remote this time of year..i use a large cap tube to run the distance as you had said to keep my volume down and then connected to my main cap tubes......this give me the coldest single compressor temps i can reach..with a outside ambeiant temp of between 10f and 20f i can reach -82f on the evaps with some fine tuning and -70f with a load running 3d benches...

to be honest remote is the way to go for large scale benching....i set mine outside the window on a window mount and run the hoses inside.

[Gary Lloyd]

this give me the coldest single compressor temps i can reach...

Have you tried R410A in it? You'll probably have to change it in the spring, but in the meantime... :D

[bowman1964]

Originally posted by Gary Lloyd
Have you tried R410A in it? You'll probably have to change it in the spring, but in the meantime... :D

naaa...not yet....i need to go ahead and pick up a can soon.have a few conversions to work on so i need some.

one is a pelt cooled cascade prometia....your idea remember:D

[Gary Lloyd]

Can't wait. Vicarious thrills... LOL

[Gary Lloyd]

with a outside ambeiant temp of between 10f and 20f i can reach -82f on the evaps with some fine tuning and -70f with a load running 3d benches...


I keep telling people to build a window A/C chiller and then stick it in the window. :D

[DaBit]

Most of us live at home and have parents :D

[bowman1964]

yea a window unit is the way to go...really it is the most effecient way to do it...just has to be supported..but thats not a big deal.

why does everyone wants to make this harder than it is;)

[bowman1964]

Originally posted by DaBit
Most of us live at home and have parents :D

i forget that sometimes.....you proberly right...dont want to tear up dads house...;)

[berkut]

Oh and i forgot 1 thing... If your cooler isnt bullet proff, in a steel cage, mounted to the house with god knows what or at least 4-6m above the ground - you wont see it longer than +- 2 weeks on your wall...

[Gary Lloyd]

yea a window unit is the way to go...really it is the most effecient way to do it...just has to be supported..but thats not a big deal.


Yep, a cheap ghetto cascade, with mother nature providing the high stage, for people who don't live in bomb shelters.

[DaBit]

Originally posted by bowman1964
i forget that sometimes.....you proberly right...dont want to tear up dads house...;)

Oh, we have no problems tearing up dads house. Dad is the one complaining.

And now I live on my own with my girlfriend, and that's even worse than daddie and mummie... (regarding mounting cooling stuff through the window, that is)

[bowman1964]

Originally posted by DaBit
Oh, we have no problems tearing up dads house. Dad is the one complaining.

And now I live on my own with my girlfriend, and that's even worse than daddie and mummie... (regarding mounting cooling stuff through the window, that is)

DABIT.....i laughing my butt off on that one:lol:

you are so right....i forgot since i have a ex wife..and the girlfriends cannt say too much yet....until they get hold of me for good.so until that happens....i will party on...LOL.

but with a little work you could make a nice inclosure outside of a window...take a old window ac unit.clean up the case and a nice coat of paint...put your high output compressor/condesor outside and a clean hose install and you got a killer setup:D

[DaBit]

Well, I still prefer everything in one case, but that's personal. Mounting stuff outside is so... definitive.


That's why I am cursing all night long while trying to cram my cascade in the limited space available for it.

[bowman1964]

Originally posted by MickeyMouse
but how can the suction line be longer than the cap tube?? if ya run 12ft of .28in tube thur the suction hose thats fine if the suction is 12ft but what if ya need 14ft?? adding more cap tube will pull more vacum but then you can loose total heat removel or so on correct??


well this a great question,i am suprised someone asked about it..you had to think about that one a sec...LOL

well sorta...if your cap tube is connected to the condensor assm.

but what i run and gary is talking about is where my cap tubing starts at the manifold(since its on my triple evap)so i can roll up the extra i have around my manifold...there is nothing saying you have to run the cap tubing all the way to the compressor assm.

i have a feed tube running from the drier to my cap tubing.this tube is small but not small enough to affect my refrigerant flow.it is small to just keep the amount of refirgerant in the system to a minimum amount of liquid without having to much...you want the least amount of refigerant you can get by with to do the cooling you need.

i think my feed tube is about 10ft long,it then has a 3 cap tube connection where it splits off into each return hose from the evap.

[bowman1964]

i dont think you understand what i am talking about yet....

i will see if i can find a picture to show what i mean..:)

[DaBit]

You can do this in two ways:

1) select a larger ID captube so you need a longer length. Thus 6ft of .028 instead of 4ft .026, for example.

2) Use an 1/4" pipe to transport the refrigerant inside, then use a captube.

A more sophisticated variant of #2 would be to use, for example, .065" captube instead of 1/4" line. This would lower the amount of refrigerant needed since less liquid is present in our 'liquid line'.

[bowman1964]

Originally posted by DaBit
You can do this in two ways:



A more sophisticated variant of #2 would be to use, for example, .065" captube instead of 1/4" line. This would lower the amount of refrigerant needed since less liquid is present in our 'liquid line'.

you got me...thats it...thats how mine is run excatly

i have made 3 or 4 systems like that...i personlly like it that way even for short distance when using muliple evap and muliple cap tubes..give be a junction point easier for me to adjust my cap tubing

[Gary Lloyd]

but how can the suction line be longer than the cap tube?? if ya run 12ft of .28in tube thur the suction hose thats fine if the suction is 12ft but what if ya need 14ft?? adding more cap tube will pull more vacum but then you can loose total heat removel or so on correct??



Lengthen the liquid line and/or the cap tube (using larger diameter equivalent length). But keep in mind that the cap tube should be no longer than 16 feet.

If you are using a large cap tube for the liquid line, there should be no substantial pressure drop from one end to the other. A pressure drop will cause a temperature drop, so you can test this by looking for a temperature drop from one end to the other. a few degrees might be acceptable.