134 Freon Question
Instructor
Joined: Feb 2006
Posts: 118
Likes: 25
From: Killearn Scotland
A refrigeration engineer sticks his nose in....
Don't know what the availability is like over there, but here in the UK, there is an R12 drop-in replacement refrigerant. Its 'R' number is R413A, but it is also known as Isceon R49. This would be my first and only choice if I had an R12 system need re-charged.
Because it is a drop in refrigerant, it does not need the ester oil that R134a requires, so just leave the old mineral oil in the system.
Remember to fit a new drier and confirm your system is gas-tight with a nitrogen pressure test at 100psi (use a soapy bubble solution to check for leaks and ensure no drop in pressure over a minimum of 12 hours).
Then fully evacuate the system and recharge.
This rule of thumb is a useful if slightly crude way of determining superheat. Ideally the evapoator outlet temperature should be about 8degs higher than the calculated evaporating temperature for the given evaporating pressure of the refrigerant you're using. You need gauges with the correct temperature scale and a thermometer to confirm this.
Most auto systems operate an expansion valve which should already be adjusted to maintain this superheat. All you need to do is charge the system until the sight glass on the liquid line (usually part of the drier assembly) runs clear with no bubbles. Be sure to keep the engine revving at about 1200rpm to ensure the compressor is pumping well.
On commercial equipment the swap from R12 to R134a is a very lengthy (costly) task it involves draining and re-filling the system several times over with ester oil to ensure the mineral oil content is reduced to less than 0.1%. Only then should you re-claim, evacuate and re-charge with R134a.
If you insist on going the R134a route, then regards the higher running pressures, the difference is negligable with regards to system safety. In otherwords, if you have good condition pipework and coils, then the higher pressures will be perfectly safe.
Additionally the difference in Evaporating pressure is actually lower with R134a, unless you get up to unusually high evapoator temperatures.
Hope this helps and I haven't sent you all to sleep
Cheers,
Douglas
PS. I live in Glasgow, Scotland! Air Conditioning!
Weather proofing, de-misting and driving with mittens on more like it!
So my A/C is long gone, the windows and T-tops are enough here.
Because it is a drop in refrigerant, it does not need the ester oil that R134a requires, so just leave the old mineral oil in the system.
Remember to fit a new drier and confirm your system is gas-tight with a nitrogen pressure test at 100psi (use a soapy bubble solution to check for leaks and ensure no drop in pressure over a minimum of 12 hours).
Then fully evacuate the system and recharge.
The rule of thumb is when you have the correct amount of freon in a system, both the inlet and outlet tubes of the evaporator will be the same temperature. On R-12 to R-134 conversions that I do, we routinely see outlet duct temps in the high 30* range.
Most auto systems operate an expansion valve which should already be adjusted to maintain this superheat. All you need to do is charge the system until the sight glass on the liquid line (usually part of the drier assembly) runs clear with no bubbles. Be sure to keep the engine revving at about 1200rpm to ensure the compressor is pumping well.
On commercial equipment the swap from R12 to R134a is a very lengthy (costly) task it involves draining and re-filling the system several times over with ester oil to ensure the mineral oil content is reduced to less than 0.1%. Only then should you re-claim, evacuate and re-charge with R134a.
If you insist on going the R134a route, then regards the higher running pressures, the difference is negligable with regards to system safety. In otherwords, if you have good condition pipework and coils, then the higher pressures will be perfectly safe.
Additionally the difference in Evaporating pressure is actually lower with R134a, unless you get up to unusually high evapoator temperatures.
Hope this helps and I haven't sent you all to sleep
Cheers,
Douglas
PS. I live in Glasgow, Scotland! Air Conditioning!
Weather proofing, de-misting and driving with mittens on more like it!
So my A/C is long gone, the windows and T-tops are enough here.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Anyone know how much 134 freon should go into a 1970 vette. I know that it calls for 4 lbs. of the original R-12. However a tech guy at a vendor that I bought some of my new A.C. parts from said 2 and a half lbs. is all that should go in when its been converted to 134. Seems a little low to me. The reason I feel its not enough, is With those 2.5 lbs. I had the A.C. shop put in there, air temp coming out of registers is 69 degrees, and this is LONG before the engine reaches normal operating temp., so its not the notorious "engine heat transfer" these things are prone to. All parts are brand new and or re-bulds freshly put on, and there are NO freeze up points at any of the systems parts.POA valve and evaporater tub does get cold so there is a flow of freon through the system.
Hoping that another pound of 134 will do the trick. HELP!!!! getting late in the A.C. season now. would like to know that it is working correctly befor the fall. Help!!!!!!!!!!!!
Hoping that another pound of 134 will do the trick. HELP!!!! getting late in the A.C. season now. would like to know that it is working correctly befor the fall. Help!!!!!!!!!!!!A/C shops have numerous resources to determine how much refrigerant should be in your system, so it puzzles me why they would take a customers advice without checking and especially after it failed to cool normally. It would simply just make me leary of their skills in a/c work. Was the poa reset for 134a?
The temps and pressures should be checked around 1200 to 1500 rpm and yes there can be a drastic difference between that and idle, hence the use of a poa or the newer variable oriface tube and the newest variable compressors.
An a6, which you should have, requires PAG 130 which is uncommon, so PAG 150 (11 Oz) is substituted for waranty purposes. Ester oil, which is compatable with 134a is not recommended in an a6 and will not be waranted.
If ALL your parts were new then this leads to an oiling problem from your description. Reman compressors usually had sealing problems although anyhting is possible.
I agree with big_G For the superheat to be correct, the inlet and the outlet temp of the evaporator shoulkd be within 1° of each other.
The 8° description is for some systems where the inlet tube is inaccessable and the vent is used instead. This is just a guess and varies with different vehicles and types of installations, but is still a good guess.
As far as the drop in replacements, many people have used them, but due to the chemical composition NONE of them return oil to the compressor nearly as well as R12 or 134a. That translates into longevity and premature compressor failure..
The proper interpretation of gauges will NOT tell you if you have the correct amount of refigerant in a system, although an experienced user can get close. They will however tell you the general condition of the individual components and where any problems lie. Superheat in combo with pressures will tell you if the system is correct.
Sight glasses do not work on 134a systems. By the time it is clear, you will be slugging the compressor.
134a does run at a higher pressure than r12 but it is minimal, should only be around 10-15 psi on the high side of a proper system. In an a/c system this is negigable. Most high side safety switches are set to 325 so it is not a concern at all.
Helper fans always help all a/c systems even on a brand new $300,000 Bently. The more air, the better period.
In your case switching to a parallel flow condenser, that is 30% more efficient, will help your system dramatically. $140.00 well spent.
Now that your compressor crapped, you must start over and flush everything properly, replace the drier and compressor.
Most shadetree mechanics can do some necessary repairs and get the system to cool.
What separates the girls from the boys is how long it will last.
Most failures don't even show up for a couple of months as can be evidenced by some recent post in this forum.
Take it back to the shop that filled it and see what they offer?
Good luck.
Thread Starter
Instructor
Joined: Feb 2007
Posts: 190
Likes: 0
From: shrewsbury Pa.
Squirrelguy, where in PA are you...i have a shop in Paradise, east of Lancaster. if you wanna come by, bring the new compressor, we'll hook up my gauges...where did you get Compressor from?? pep boys or napa? did you get new or reman....NEVER buy reman, there is a reason reputable Compressor manufacturers do not sell reman
Thread Starter
Instructor
Joined: Feb 2007
Posts: 190
Likes: 0
From: shrewsbury Pa.
Sorry to hear about your compressor. Prior to all the work you had done was the system operating or was there a problem that required the complete overhaul? The reason I am asking is if the mechanic that did all the work failed to flush out your system properly and some trash or metal from the system was not flushed out properly you may have a reason to go back to the shop that did the work and maybe they will make good on the recharging of the system
Thread Starter
Instructor
Joined: Feb 2007
Posts: 190
Likes: 0
From: shrewsbury Pa.
First of all, sorry to hear of your problems.
A/C shops have numerous resources to determine how much refrigerant should be in your system, so it puzzles me why they would take a customers advice without checking and especially after it failed to cool normally. It would simply just make me leary of their skills in a/c work. Was the poa reset for 134a?
The temps and pressures should be checked around 1200 to 1500 rpm and yes there can be a drastic difference between that and idle, hence the use of a poa or the newer variable oriface tube and the newest variable compressors.
An a6, which you should have, requires PAG 130 which is uncommon, so PAG 150 (11 Oz) is substituted for waranty purposes. Ester oil, which is compatable with 134a is not recommended in an a6 and will not be waranted.
If ALL your parts were new then this leads to an oiling problem from your description. Reman compressors usually had sealing problems although anyhting is possible.
I agree with big_G For the superheat to be correct, the inlet and the outlet temp of the evaporator shoulkd be within 1° of each other.
The 8° description is for some systems where the inlet tube is inaccessable and the vent is used instead. This is just a guess and varies with different vehicles and types of installations, but is still a good guess.
As far as the drop in replacements, many people have used them, but due to the chemical composition NONE of them return oil to the compressor nearly as well as R12 or 134a. That translates into longevity and premature compressor failure..
The proper interpretation of gauges will NOT tell you if you have the correct amount of refigerant in a system, although an experienced user can get close. They will however tell you the general condition of the individual components and where any problems lie. Superheat in combo with pressures will tell you if the system is correct.
Sight glasses do not work on 134a systems. By the time it is clear, you will be slugging the compressor.
134a does run at a higher pressure than r12 but it is minimal, should only be around 10-15 psi on the high side of a proper system. In an a/c system this is negigable. Most high side safety switches are set to 325 so it is not a concern at all.
Helper fans always help all a/c systems even on a brand new $300,000 Bently. The more air, the better period.
In your case switching to a parallel flow condenser, that is 30% more efficient, will help your system dramatically. $140.00 well spent.
Now that your compressor crapped, you must start over and flush everything properly, replace the drier and compressor.
Most shadetree mechanics can do some necessary repairs and get the system to cool.
What separates the girls from the boys is how long it will last.
Most failures don't even show up for a couple of months as can be evidenced by some recent post in this forum.
Take it back to the shop that filled it and see what they offer?
Good luck.
A/C shops have numerous resources to determine how much refrigerant should be in your system, so it puzzles me why they would take a customers advice without checking and especially after it failed to cool normally. It would simply just make me leary of their skills in a/c work. Was the poa reset for 134a?
The temps and pressures should be checked around 1200 to 1500 rpm and yes there can be a drastic difference between that and idle, hence the use of a poa or the newer variable oriface tube and the newest variable compressors.
An a6, which you should have, requires PAG 130 which is uncommon, so PAG 150 (11 Oz) is substituted for waranty purposes. Ester oil, which is compatable with 134a is not recommended in an a6 and will not be waranted.
If ALL your parts were new then this leads to an oiling problem from your description. Reman compressors usually had sealing problems although anyhting is possible.
I agree with big_G For the superheat to be correct, the inlet and the outlet temp of the evaporator shoulkd be within 1° of each other.
The 8° description is for some systems where the inlet tube is inaccessable and the vent is used instead. This is just a guess and varies with different vehicles and types of installations, but is still a good guess.
As far as the drop in replacements, many people have used them, but due to the chemical composition NONE of them return oil to the compressor nearly as well as R12 or 134a. That translates into longevity and premature compressor failure..
The proper interpretation of gauges will NOT tell you if you have the correct amount of refigerant in a system, although an experienced user can get close. They will however tell you the general condition of the individual components and where any problems lie. Superheat in combo with pressures will tell you if the system is correct.
Sight glasses do not work on 134a systems. By the time it is clear, you will be slugging the compressor.
134a does run at a higher pressure than r12 but it is minimal, should only be around 10-15 psi on the high side of a proper system. In an a/c system this is negigable. Most high side safety switches are set to 325 so it is not a concern at all.
Helper fans always help all a/c systems even on a brand new $300,000 Bently. The more air, the better period.
In your case switching to a parallel flow condenser, that is 30% more efficient, will help your system dramatically. $140.00 well spent.
Now that your compressor crapped, you must start over and flush everything properly, replace the drier and compressor.
Most shadetree mechanics can do some necessary repairs and get the system to cool.
What separates the girls from the boys is how long it will last.
Most failures don't even show up for a couple of months as can be evidenced by some recent post in this forum.
Take it back to the shop that filled it and see what they offer?
Good luck.
Pro
Joined: Jul 2005
Posts: 720
Likes: 1
From: Holtwood PA
Bought the compressor from Ecklers, Was an A.C.Delco re-build. I live in Shrewsbury Pa. and would like to come to your shop on a Monday once the new compresser comes in andI get it on. i know where Paradise is. Where exactly are you located there. I say Monday because thats my day off. Thanks for the offer. Any Idea who sells these things brand new and about how much they run?
