Compressor stripped from a portable a/c

[CrazyDr]

Hi everyone, this is my new project:

I wanted to build a water chiller but instead of getting a fridge or a freezer i found a portable a/c delonghi PAC F14, that has a total freezing capacity of 1900W (6.500 btu).
I stripped the compressor (running with 0.490gr of R22) and the fan (... it's really big, seems like a jet motor, 93W of consumption..) and i put the evaporator into the freezer compartment stripped from a real fridge (it's big but has a capacity of nearly 25lit, totally insulated: the walls are 8cm thick!).
The system after 20min can lower the water temperature to 9-10 C (from 23 C of ambient temperature).

Why doesn't get near 0 C? Maybe it needs time...? Maybe 25lt are too much for the compressor?

Is it possible that the compressor has to be refilled?? The guy from whom i bought it said that has to be recharged..

If i decide to refill it should i replace the evaporator with a waterblock and apply it directly to the CPU?

Thanks everyone, Bye

[Warlord2]

COOL great grab, yeah those temps do seem a little weird, if its r22 you should be going WAY lower than that, prolly about -30 or so. umm maybe there is a thermal shut off or at a certain evap temp is reached the compressor turns off or the TEV will auto change so it doesnt cool so much.

my guess would be that the TEV changes sense its not allowing you go get below freezing point.

(how am I doing bowman, did I get even close??)

do you have air moving through the condensor?

[CrazyDr]

Yeah, the air is moving through the condensor by that BIG fan that i described, it gets hot but not that much.

Maybe i am trying to cool too much water, 25 lts...

Ah, the tubing (made of copper) of the compressor does get very low, near -20, it's the water that doesn't get very cold (now it's ab 6 C).

The reservoir is ALL sealed, in a freezer compartment..

Btw, the water, is it moving inside the reservoir?? I mean, does the warm water go to the top and the cold one to the bottom?? Cause, my temperature sensor (a Senfu digital one) indicates that the water temp gets higher for a minute and then lower again, and this is being repeated again and again..

Thans everyone!!

[ssjwizard]

if the owner said it needs to be recharged thats probably it insufficant flow of refridgerant through the evaporator to cool the tub of water.

personaly id take out the condensor and compressor and rebuild the entire system

[CrazyDr]

ssjwizard this is exactly what i am going to do before recharging the system but for the time being i want to squeeze down the system left like this.

New data: the water temp (MIN) remains at 5.9 but this time the evaporator and the water around it became an ice cube after just 30 minutes..

Maybe the prroblem is the fact that i am working with plain water.. If i change to methanol-distilled water it should get lower, no?

[aenigma]

Originally posted by CrazyDr
ssjwizard this is exactly what i am going to do before recharging the system but for the time being i want to squeeze down the system left like this.

New data: the water temp (MIN) remains at 5.9 but this time the evaporator and the water around it became an ice cube after just 30 minutes..

Maybe the prroblem is the fact that i am working with plain water.. If i change to methanol-distilled water it should get lower, no?

Exactly, you cant test temps with plain old water, you need to use methanol/antifreeze etc.

[DrMac]

Very cool. I have my watercooler running through a Culligan watercooler (drinking water), using it as a resevoir, after it passes through the radiatior.

[Warlord2]

why cant you use normal water? wouldnt it just feeze if it gets below 0c?

[aenigma]

Originally posted by Warlord2
why cant you use normal water? wouldnt it just feeze if it gets below 0c?

Yeah thats why you cant use it, if the chiller is capable of -20c then its just going to freeze the water....So you cant get an idea of water temps to expect...

[ssjwizard]

also try to get more flow around/through the evaporator that will drop your temps alot too.

[CrazyDr]

Ok, i've changed the coolant: methanol + water 33:66, as soon as i get home i'll see the results and i'post them.

ssjwizard, i allready have a VERY large fan of 93W ducted on the evaporator, the airflow is really high..

Thanks everyone, stay tuned!

[ssjwizard]

ok you have a fan on the evaporator???? i thought you had the evaporator inside of the resivior. putting the evaporator directly into the coolant will get you substantialy better tempratures. if your using air to cool your coolant from the evaporator your going to loose alot of efficancy

[CrazyDr]

Sorry, my mistake, the fan is ducted directly to the condensor..

What do u mean ssjwizard?? That i should put a fan inside the freezer..? The evaporator is sinked inside the reservoir..

The temps are getting better: methanol + water 33:66 got my temps lower, near 5 C.

is it normal that the temp goes lower when i turn off the compressor...? I should say that my reservoir is inside the freezer and it's smaller that the freezer, only the half of the evaporator is sinked in it..

Any ideas??

Should i take off the reservoir and fill all the freezer with water-methanol, then seal it up...?

[khman002]

sounds good

[ssjwizard]

ok im kinda lost now. some pictures or a descrption of exactly how everything is set up would help.

[aenigma]

Originally posted by CrazyDr
Sorry, my mistake, the fan is ducted directly to the condensor..

What do u mean ssjwizard?? That i should put a fan inside the freezer..? The evaporator is sinked inside the reservoir..

The temps are getting better: methanol + water 33:66 got my temps lower, near 5 C.

is it normal that the temp goes lower when i turn off the compressor...? I should say that my reservoir is inside the freezer and it's smaller that the freezer, only the half of the evaporator is sinked in it..

Any ideas??

Should i take off the reservoir and fill all the freezer with water-methanol, then seal it up...?
Hmm ok after mixing it with methanol your still getting sucky temps hmmm.Ok is there any ice on the evaporator at all?Is the condenser warm at all?How long did you let it sit chilling the water, do you have the thermostat in the water?Does the compressor kick off?
Some pictures would be nice.This system should be capable of at least -20c.Did the evaporator frost up all the way back to the compressor before you repositioned it into the res.Also what do you mean by freezer?

[CrazyDr]

Ok, this is an exact description of the system:

I have the whole block compressor-evaporator-condensor (both of evaporator and condensor are in a radiator-like form) stripped from a portable a/c system capable of 6500 btu and charged with R22. A large fan, part of the a/c system is ducted to the condensor.

Then i also stripped the freezer part of a normal fridge: i mean that i cut off all the fridge and i took only the freezer part, complete with the door and all the insulation but without any compressors... lets say that its a "passive" freezer, something like a 37lit reservoir all insulated (7cm thick).

At first i filled this "freezer" with plain water and i submerged the WHOLE evaporator in it.. the cover could'nt close and this way the temps wer'nt that good, near 12 C.

Then i closed the cover and i insulated it all over, with the evaporator always sinked in the freezer's water: after 20min the evaporator and the water around it became a large ice cube and the water temp got lower, near 4 C. I turned off the compressor and the temps keeped getting lower, near 2 C.

Then i changed coolant: methanol + water 33:66, but this time i didn't put the coolant directly into the freezer cause i got less methanol that needed and the evaporator couldn't get sinked in it. This way i used a smal reservoir inside the "freezer" filled with coolant and the evaporator immerged in it by only half (maybe less than half). Temps have got near 0 and when i turn off the compressor get near -2 C.

Now the sensor indicates -3 after 20mins and with a starting temp of 4.

aenigma:
The evaporator get iced but only sometimes, and not very much, except that time with the plain water that freezed all over.

The condensor gets warm but the fan cools it back very rapidly. If i turn off the fan it gets really hot.

I let it chilled max for 30-40 min.. usually 20-30min..

I have a thermostat, the one that came with the a/c, with its sensor sinked in the coolant along with the sensor of the digital thermometer (senfu). The thermostate isn't digital and it hasn't any temps on it..

I dont' understand what do u mean with "kick off", it does make some noise but nothing strange, sounds like the freezer compressor..

I'll definetelly post some pics, i have to get my friend come here with his digital cam..

Btw, thanks everyone for the help!!!

PS: After 32min the temp got to -5 C, compressor still on.. and it's getting lower..

F..., the compressor stopped all by itself at -5.8 C after 36min, i think the thermostate has reached its lower point.. i'll get it off the reservoir..

[ssjwizard]

yes one of your limiting factors is going to definatly gona be a thermostat. another thing is that we forgot to consider that they overcharge A/C units for higher heatload but this raises the boiling point of the unit depending on how much its overcharged that could be the reason your temps arent that low. another is that its under charged and there isnt enough liquid going into the evaporator fast enough to move the heat consistantly. it should only take 2-3 minuites for it to get realy cold.

[CrazyDr]

The thermostate problem has been solved, i placed the sensor inside the freezer but not in the coolant: the temps are -9 C.

Tomorrow i'll fill the whole "freezer" with coolant (no reservoir in it), this way the evaporator will be fully submerged.

I'll post the details, thanks eveeryone!!

[Warlord2]

-10 sounds better, once the evap is all submerged it should be a kick a$$ system:)

I WANT SNAP SHOTS

I WANT SNAP SHOTS

I WANT SNAP SHOTS

I WANT SNAP SHOTS

I WANT SNAP SHOTS!!!!

[aenigma]

Ok it sounds like your temps are just slowly dropping.An a/c unit should be getting you temps of about -20c....
Sounds like you have a ton of liquid to chill.

[country_3030]

Do you have your condensor inside of the frezzer? If so you could put it out side of the frezzer to get cooler temps. Your condensor is where the ac system gets rid of heat.

[kenji]

how does one go about filling a gas system like that?

[country_3030]

You need the proper gauges to make sure you don't cause your compresor to quit due to to much presure. My grandad could explain it better. He is a retired cooling system repair man.

[kenji]

think you could ask him how to do it for me? Can I go to a fridge repair shop and have them fill it? I mean would they do it? And how much would it cost?

[aenigma]

They should do it for you, you can get gauges for it though.And a a vacuum pump would really help too.

[kenji]

anyone who build one before, what pressure do you recomend in the system. What should be the idle pressure to which I should fill it up. And what compressor to get?

[aenigma]

Well that you will have to firgure out yourself.It depends on capillary/compressor and refrigerant mostly.You will have to find the sweet spot on your own....

[kenji]

any advice or maybe a sugested setup?

[aenigma]

It is kind of hard to give advice, my only advice would be just dive right in.You will learn :)
And you will learn from any mistakes you might make.BTW R290 (propane) is a good cheap refrigerant.

[kenji]

thanks, btw whats the boiling temp of R290 (propane)? bout -40?

[aenigma]

Yep about -42c

[CrazyDr]

Aenigma, my compressor is charged with R22, could i also use R290 with it?? Do u think that the guys that recharge air-conditiong systems have also R290..? Where i live (currently i stay at Rome, Italy) a special permitt is needed for getting a can of Rxxx...

Using R22 and 30lit of coolant (methanol+distilled water), with the evaporator fully submerged, got me to -18 C after less that 40mins (it was still getting lower..), nice, eh??

Why the temps keep going lower after i turn off the compressor..?

I am expecting a new waterblock (a copper one, the koolance really sucks..), a pump (a Sicce1300 will sostitute my Eheim 1060 for a while..), tubes ecc.

Then i'll see how i can insulate all tubes and wb... any good article..?

Hope i won't fry my new A7V333... :mad:

[CrazyDr]

And what about the fact that r290 can explode...??

[Warlord2]

ow ow I can answer this one!

propane can explode, but it needs to have oxygen to expode and when we vacuum out all the air in the system, no bomb no more!

unless it leaks out, that would be bad, but it still word take a spark or a flame to start it.

[aenigma]

Dont worry about it exploding, I have had a room full of it.But be warned it smells like ass! :p
It could explode, but I havent had that happen yet.I have caught pipes on fire after emptying them out having a little propane left in it, pain in the ass when your trying to braze a pipe together...
R22 is better than R290...
What kind of system do you have?Is it like a condenser unit or an a/c or what?If it does only get to -18c or so and doesnt drop any farther, It might be charged wrong.Were you getting any frost on the suction line that returns to the compressor, or on the compressor itself?

[kenji]

here is a list of all the common refrigerants I got from one of the articles... I want to use R170 (ethane) ,a boiling point of -88C, molecular weight of 30. Is it hard to get?


"These are what I consider a Class 1 refrigerant. By this, I mean they were manufactured for the purpose of being used as a refrigerant and will require a certification to acquire. These require no additives to compress properly, have a long life span and are for the most part non combustible, BUT they do release chemicals which are dangerous to the ozone layer.

Here is a list in order of common use.

R12 (dichlorodifluoromethane) was the standard in refrigeration for a long time. With a boiling point of slightly under -21C, it was used widely in automobiles, refrigerators, window air conditioners - just about everything.

R22 (chlorodifluoromethane) is the refrigerant that has held the standard for home air conditioning longer than any other and is still in use. Its boiling point is just under -40C.

These refrigerants have been in use for years and have been proven time and again reliable and efficient; their only down side is they deplete the ozone layer and thus require special certification. As a result, they are typically only available in 30lb or larger canisters. These refrigerants come pre-bottled with mineral oil, so your compressor will need to be adjusted accordingly.



Class 2 refrigerants are refrigerants that are commonplace and easy to acquire. These do not require special certification nor do they damage the ozone layer.

R134A(,1,1,2-tetrafluoroethane) has a boiling point of only -26C; it is becoming the new standard in refrigerators, automobiles, and all other common uses.

R290 (propane) is also beginning to make its way in as a mainstream refrigerant. With a boiling point of -42C, it is more of a class 4 refrigerant, but because of its new found common use I have included it in my class 2 list. This is randomly used in things such as freezers - a lot of hobbyists use it for home built systems.

These refrigerants are quite affordable; also to be noted is that they come bottled alone or with ester oil, require no certification and do not damage the atmosphere. As a result of these factors, they are readily available to the public.



Class 3 refrigerants are those which have a lower boiling point than standard refrigerants. Often they are hybrid mixtures of class 1, 2 and 4 refrigerants.

R404B (pentafluoroethane/1,1,1-trifluoroethane/1,1,2-tetrafluoroethane: 44:52:4%) This is one refrigerant often sought after by overclockers. With a boiling point of approximately -44C and available in 12oz cans, this can be a nice choice provided you have your certification.

R409A (chlorodifluoromethane/2-chloro-1,1,1,2-tetrafluoroethane/1-chloro-1,1-difluoroethane: 60:25:10%) This refrigerant has a boiling temperature of -47.8C; you have to purchase 30lb cans.

R508B (trifluoromethane/hexafluoroethane: 46:54%) This is one of the best readily available high end refrigerants there is. With a boiling point near -50C, you are lucky to acquire this.

R-14 (1,2-dichloro-1,1,2,2-tetrafluoroethane) Ranking in with a boiling temperature approaching that of -150C at 1 bar pressure, this refrigerant can deep freeze you faster than you can say lickity split. Provided you are running either a cascade cooler or are have a compressor that can withstand approximately 350psi, it's a pleasure to work with.

These refrigerants have a moderate - substantially lower boiling point than normal refrigerants. Some can be acquired in small amounts, others have to be purchased in 30lb cylinders.
The biggest issues with refrigerants like R14 is that with its so low boiling point, it requires a lot of pressure to compress to liquid. With this in mind, it may be better to juice up a system that is running on a lower grade refrigerant by adding 10-25% more.



Class 4 refrigerants are natural gases. These can be acquired from just about any chemical supply place - some can be located in your own home. These generally have an extremely low boiling point and are difficult to compress due to their weight, but can easily be used as an additive to an existing system to squeeze it for a few extra degrees. These, as you may have guessed, do not come packed with any kind of oil additive and therefor can be used in any system.

R50 (methane) This a moderately light gas with a boiling point of -162C; it's the base compound for most of today's refrigerants. In its pure form, it is a bit too light (molecular weight 16) to work with outside of a cascade cooler. Though this can be used in a system of its own, you will need pressures nearing the 450 mark on a warm day to liquify. Overall a great additive or for use in a cascade cooler.

R170 (ethane) This gas has a boiling point of -88C and a molecular weight of 30. It's a much more suitable stand-alone refrigerant than R50. There are a few commonplace refrigerants that are based on this gas.

R744A (nitrous oxide) This is a pretty commonplace gas these days; with a molecular weight of 45 and boiling point of -89C, this definitely yields some potential, not only as a stand-alone refrigerant but also as a cascade refrigerant.

R717 (ammonia) This is used in many commercial refrigeration systems. Although it has a rather low molecular weight (just under 18), its boiling point of -33C makes it rather easy to work with. The most widely occurring problem with this gas is its smell and, as it is slightly corrosive, extra precautions must be taken.

R740 (argon) Coming in with a weight of approximately 40 and a boiling point of -182C, it is easily compressed and, used in conjunction with 25% R134, has a weight which is easily used in a standard air condensed system to maintain a boiling temperature below that of -120C with less than 300 psi. This has a lot of common potential.

R764 (sulfur dioxide) This gas has the scores - all around molecular weight of 60 and boiling temperature of -76C, although it has toxicity issues. Given a bit of precaution not to let a lot of this loose into the air, it will easily yield quite impressive results.

These gasses have quite low boiling points, which would make them all great candidates for a cascade cooler. For those of you who don't know, a cascade cooler is simply a Phase change system that uses another Phase cooler to cool its condenser, so you can use a very low temperature refrigerant at a decent psi rating."

[aenigma]

heh damn figures someone would think they can use these refrigerants...

If you have a powerful compressor, sure you can use it.None of those refrigerantexplanation list the condensing PSI, so it could be near 400psi to condense.I would definately rule out R170....
Unless of course you can find out what psi R170 condenses at....

[ssjwizard]

OK kenji thats like the 2nd time ive seen you quote my article it would be better to just link them than to paste that entire section on refridgerants... and yes i did leave out the part on condensing points of the refridgerants it something i should add in but have not the time nor the care to find out... if you realy want to know you can send an email to a chemical supply place that deals in liquid gasses they will be able to tell you. actualy just about any gas suplier can tell you.

[kenji]

I will try, but I dont know if there is one anywhere around here... if anyone knows the condensation pressures for any of these do tell ^_^