Sciencemadness Discussion Board

AC Refrigerant Questions

MagicJigPipe - 11-5-2010 at 08:35

Got an old window AC unit (the electronics were damaged but the compressor still works). I'm going to make a water chiller with it.

I am going to get a service valve today to add refrigerant.

I have a confession to make. I cut the tubing thinking there was no refrigerant but there was. It leaked for several hours (just gas because I stopped cutting when I heard the sound).

Anyway, long story short: I need to figure out what type of refrigerant to use and what kind of compressor oil (I can't find the damn documentation that was on the inside; now where did I put that?) I am almost certain it will be R134a, however, if it requires freon should I just give up? I know that R134a is a replacement for R12 (freon) but doesn't this require flushing and a change of compressor oil?

I'm trying to get this done today (I took my last final today so I'm doing stuff now) so hopefully I can find out before 3 or so when the AC supply places close.

Thanks.

The WiZard is In - 11-5-2010 at 08:49

Quote: Originally posted by MagicJigPipe  
Got an old window AC unit (the electronics were damaged but the compressor still works). I'm going to make a water chiller with it.

Thanks.



1st. you will need a vacuum pump to pump the system
down before you can recharge and then need to know
the amount of refrigerant to add.

You will have to buy a tank of refrigerant, an amount
much-much larger then needed for one project.

Experimentalism can be financial suicide.

MagicJigPipe - 11-5-2010 at 09:17

But R134a is sold in all kinds of different amounts, why would I have to buy so much?

And what will I be pumping out? The compressor oil? Or does some refrigerant remain (and if so, how?)

The WiZard is In - 11-5-2010 at 09:26

Quote: Originally posted by MagicJigPipe  
But R134a is sold in all kinds of different amounts, why would I have to buy so much?

And what will I be pumping out? The compressor oil? Or does some refrigerant remain (and if so, how?)



You have to be absolutely sure what refrigerant is used, la
machine is designed to work with a specific refrigerant.

You have to pump any air out of the system.

MagicJigPipe - 11-5-2010 at 09:39

Okay, that makes sense.

How can I be sure of the type of refrigerant? Is it written in code on the compressor?

The WiZard is In - 11-5-2010 at 10:08

Quote: Originally posted by MagicJigPipe  
Okay, that makes sense.

How can I be sure of the type of refrigerant? Is it written in code on the compressor?



Unless it is really old - there should be a sticker listing the
refrigerant and amount used ---- somewhere.

Or ping the manufacturer.

[Edited on 11-5-2010 by The WiZard is In]

Nobel prize winners refrigerator

The WiZard is In - 11-5-2010 at 10:15

While we are discussing refrigerators I would mention in passing
the Nobel Prize winners Einstein and Szilard patented one!

I recomend :—

Gene Damnen
The Einstein-Szilard Refrigerators.
Scientific American 276:1 90&ff January 1997

Google it.

MagicJigPipe - 11-5-2010 at 10:50

Thanks. Called the manufacturer. "Alkylbenzene oil" and R22 refrigerant.

I had a feeling it might be a damn CFC...

But apparently there is a new drop-in replacement: R417a

Maybe I'll just see how much it is to have someone do it for me.

Skyjumper - 11-5-2010 at 11:23

Remember, Come about end of may, early june you can replace it and get a whole new system for around 75 to 100 at your local hardware/ general crap store. May be cheaper (and more reliable)

watson.fawkes - 11-5-2010 at 11:27

Quote: Originally posted by MagicJigPipe  
Called the manufacturer. "Alkylbenzene oil" and R22 refrigerant.
As I recall, propane is also a substitute for R22. There are a number of caveats, notably (1) that it has to be actual propane and not some flammable admixture with a bunch of propane in it and (2) you'd better be very certain of your skill at brazing refrigeration lines. This is perhaps not the best option for a first refrigeration project, but I thought I'd mention it. There's always the option of getting a refrigeration service to fill it for you, once you've got the mechanical parts done.

Refrigerant

MadHatter - 11-5-2010 at 11:33

Look for the sticker indicating the refrigerant and charge weight. If it's R134a and the low
pressure(liquid) side has a quickfit, schrader valve, like the type used in automotive
apllications, go to Walmart and buy what you need.

If it's R-12, you'll require original R-12(VERY EXPENSIVE !) or a substitute. R-12, like some
substitutes, require the EPA 608(HVAC) or 609(MVAC) license to purchase and/or handle.
I have the 609 license and use Autofrost(R-406a), license required, to charge older R-12
systems in cars.

Converting R-12 to R134a would require, in addition to the refrigerant, a replacement
PAG or POE(recommended) oil because the mineral oil used in R-12 cannot be forced
through that quickly.

P.S. If it's R-12 and you decide to switch to R134a, it's advisable to use compressed
air to blow any remaining mineral oil out of the compressor after draining due to
contamination.

[Edited on 2010/5/11 by MadHatter]

franklyn - 11-5-2010 at 12:02

Some practical advice :
( I see you already found out what it is )
There must surely be a metal tag somewhere in the unit that has
indicated what refrigerant it contains. You can always Google the
manufacturer for info , they must have a customer service line.

Automotive shops sell aerosol cans of replacement refrigerant.
The real question is how much to put in ? You will need required
gauges and couplings to apply vacuum and charge the unit with
refrigerant.
Not being an air conditioning service and repair technician you
may just be better off finding a shop that will quote you a price
to do the job for you if you bring the unit to them.
Your best course :
Check what may be dumped or recycled locally and just start out
with a working unit.

Youtube has videos available to show what you are taking on.
This selection has links in the margin to many others

Charging and Evacuating A/C systems part 1
http://www.youtube.com/watch?v=ma_jHmV3gcw
Charging and Evacuating A/C systems part 2
http://www.youtube.com/watch?v=sbveNeazWo8
Charging and Evacuating A/C systems part 3
http://www.youtube.com/watch?v=IjYWsgBx7Hw
Charging and Evacuating A/C systems part 4
http://www.youtube.com/watch?v=TWNEKI2P1uc
Charging and Evacuating A/C systems part 5
http://www.youtube.com/watch?v=6jcTdpUtsLs

.

Sedit - 11-5-2010 at 12:37

IF I remember correctly R22 is whats needed for a window unit but the standards change often and we just had to completely change all out equipment around because law is forcing in a new Refridgerent for central air units which runs under insain pressures.

The pumping down that Wizard spoke if is mainly done to remove water from the line by pulling a large vacume on the system but in the process creates freespace for the induced freon to go.

I mostly do large units and I suggest having a quick chat with your local car mechanic since Im sure he could walk you thru the process since cars use a system more simular to a window unit.

The WiZard is In - 11-5-2010 at 13:01

Quote: Originally posted by MagicJigPipe  
Got an old window AC unit (the electronics were damaged but the compressor still works). I'm going to make a water chiller with it.

Thanks.



On da technical side — what makes air conditioning/refrigeration
work is the Thermal expansion valve each designed for a specific refrigerant.

Google it.

There was a very good series of articles on refrigeration in
(of all places) The National Fisherman some years back.

MagicJigPipe - 11-5-2010 at 13:43

This is interesting. The copper tubing they sold me seems much more pliable than the stuff that was already connected to the unit (this was at the AC place). I trust them though.

I'm stuck until tomorrow on putting the rest of it together b/c they didn't have any 1/4" Cu couplings at Depot of Homes (yes, I forgot to get it at the AC place).

I guess I will have to completely replace the capillary tubes as I don't see a way to "couple" them.

I know this seems like a lot of work that could be skirted with a little cash but part of the point is to become somewhat familiar with a small refrigeration system.

Thanks for all the replies.

azo - 11-5-2010 at 15:04

hi magic

look at the charge fitting if it is small it would proberly be R12 which is unavailable these days because of it being ozone depleting. If it is R12 you can replace it with 134a easerly by draining the compressor oil and replacing it with a synthetic ester oil like pag as hatter said.On cars you need to change conection seals to a green seal which can stand higher temperatures and pressure. to change a R12 system to 134a you can buy adapters to fit onto the charge conectors to allow you to connect a set of 134a gauges to it . Unless you are diagnosing a fault you would only need to connect the suction side hose and pull the system to a negative vacume about -10 inches of mercury for about 1 half and hour to remove any moisture in the system then close of your gauge and let it sit for at lease 1 hour to see if it holds vacume if it holds vacume then you are ready to go start the compressor and slowly open the low side gauge and start to charge the system once you added a small amount you lock of the valve and check your reading on the gauge if it don't come down to the right reading you then charge it a bit more and do this untill you get the required reading on your low side gauge , its that simple. But saying this being a wall AC it would proberly be R22.
as for the function of the TX valve it is there to convert the refrigerant from a liquid to a gas before the refrigerant goes back to the compressor as you well no you can't compress a liquid .
How it works is the refrigerant leaves the compressor as a gas which then goes through the condenser and gets converted to a liquid and then goes back to the evaperator as a liquid and then through the TX valve being converted back to a gas before entering the compressor
there is also a reciever drier as well to remove moisture .
if you over charge a retrofit R12 system due to the increased presure created it will proberly just trip the compressor out because of the high pressure cut of switch is activated.

hope this explains how an ac works pretty simple realy.

regards azo::P

MagicJigPipe - 11-5-2010 at 15:42

Thank you azo. I am pretty familiar with the "theory" of operation, I just don't have practical, hands-on experience.

undead_alchemist - 11-5-2010 at 22:51

R12 you can use a mix of ISOButane and Propane.
R22 you can use Propane.

I have parts for both system types laying around, and have used Propane many times to charge projects with.
Largest system that I have charged with Propane used a 20K BTU compressor.

It also helps to have a refrigeration manifold gauge and hoses.
Also you cant use regular solder ether. You need a brazing alloy. Sil-Phos 15, Silver solder or simular.

azo - 12-5-2010 at 01:37

Magic if you need any help with doing this just ask i am a third generation traded automotive mechanic with 25 years experience

as the last post said you can use propane just don't do it to cars
big hazard if the evaperator leaks.

regards azo

MagicJigPipe - 12-5-2010 at 21:16

Just so everyone knows: I found out tonight that 1/2" "refrigeration grade" Cu tubing will not work with 1/2" "plumber's" Cu fittings. The fittings end up being way too big. It seems like you should subtract about 1/8" from the size of the tubing to get the right size fitting. So, I needed 3/8" fittings for 1/2" tubing (which happens to not be carried by Home Depot so I have to wait 'til tomorrow).

Seems kind of ridiculous to me but I'm sure there is a (good?) reason.

[Edited on 5-13-2010 by MagicJigPipe]

12AX7 - 12-5-2010 at 21:30

Yes, tubing is net size, PIPE is nominal size. The copper pipe used for plumbing is pipe, not tubing, hence `1/2"' is actually 0.625" nominal, etc.

By a fortunate decision, copper pipe sizes less than 2" are only 1/8" over the nominal number, so you simply need a 3/8" fitting.

Historically, pipe has been nominal, supposedly to keep the i.d. constant or something as materials and techniques changed. Like most imperial standards, the numbers are inconsistent and require tables to keep track of, and the reasons are not very solid and up for speculation.

Tim

[Edited on 5-13-2010 by 12AX7]

undead_alchemist - 13-5-2010 at 20:13

Quote: Originally posted by 12AX7  
Yes, tubing is net size, PIPE is nominal size. The copper pipe used for plumbing is pipe, not tubing, hence `1/2"' is actually 0.625" nominal, etc.

By a fortunate decision, copper pipe sizes less than 2" are only 1/8" over the nominal number, so you simply need a 3/8" fitting.

Historically, pipe has been nominal, supposedly to keep the i.d. constant or something as materials and techniques changed. Like most imperial standards, the numbers are inconsistent and require tables to keep track of, and the reasons are not very solid and up for speculation.

Tim

[Edited on 5-13-2010 by 12AX7]


This is the reason why when I am at the refrigeration supply I always stock up on the common fittings, eBay can also be good go get some deals. Have gotten full boxes of things like sight glasses and filter-dyers for the price of 1 at the supplier.

I hold both a US 609 ticket for cars, and a BC Number for buying local. It is well worth having them.
Might also go for a US 608 Small appliance ticket later.

Also a note for Canada, Lordco and Walmart only seem to carry Duracool. Duracool is a propane and butane mix. It is also legal to use in cars here.

MagicJigPipe - 13-5-2010 at 23:21

What kind of compressor oil should I use with the propane?

undead_alchemist - 13-5-2010 at 23:56

Mineral Oil works with propane.
Make sure to get oil that is the right grade for you compressor.


[Edited on 14-5-2010 by undead_alchemist]

quicksilver - 14-5-2010 at 08:04

I've done something VERY similar to what you are doing and it turned out to be financially wasteful. I went with a small Home Depot refrigerator for $49 and saved a LOT of hassle and time. You know what I'm talking about; the little square dormitory-style refrigerators that are about 3' square...You take them apart and the coils are almost perfect for a "sheep feeder" (galvanized trough, 18" x 3') to use as a cooling bath.

MagicJigPipe - 14-5-2010 at 08:12

Yeah I was just thinking the same thing. Is it easy to bend the tubes into a "custom fit"? That's the biggest issue. It's not much use if it MUST stay in the same configuration.

MagicJigPipe - 14-5-2010 at 18:48

The cheapest one I found at the big box stores: here