PaulRainbow
Well-Known Member
All car air-con running on R134a leaks, they need periodic servicing (re-filling).
R134a refrigerant
- Thread starter KAM
- Start date
All car air-con running on R134a leaks, they need periodic servicing (re-filling).
Yngmar
Well-Known Member
1 Kg R134a REFRIGERANT GAS (no oil)
I doubt they actually check for the certificate. If they do, move on to the next one. I bought an identical looking bottle last year from another seller (no longer on eBay, but still on the web) and the fridge has been running fine ever since. Of course all done professionally by people with stacks of certificates :eagerness:
I doubt they actually check for the certificate. If they do, move on to the next one. I bought an identical looking bottle last year from another seller (no longer on eBay, but still on the web) and the fridge has been running fine ever since. Of course all done professionally by people with stacks of certificates :eagerness:
lw395
Well-Known Member
Some leak more than others.
Mine has never needed a refill, and the car is nearly 10 years old.
Once they lose pressure completely, the leaks seem to get worse.
I've known a few people have their aircon 'fixed' sometimes it's good for a few years, sometimes it barely gets through the summer. One banger I owned, I had it regassed, it worked for about a fortnight.
A typical car needs over 600g of R134a. A typical top-up can holds maybe 130g. So maybe enough to go from 'just about working', to 'working properly'?
For cars, I think the gas is now so expensive, it's not worth chucking it in and hoping, you want the system vacuumed out, pressure tested for leaks and properly filled. You're looking at £60+ worth of gas, so paying the man with the proper tools to do it right makes sense.
There are a of course a lot of cowboys out there who will charge for a proper job and just chuck a bit of gas in.
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superheat6k
Well-Known Member
This is generally because the compressor on a car is driven off the engine and so has a shaft seal. These leak mostly due to poor system practices - a small amount of air left in the system introduces moisture (all air contains a small amount of moisture). In turn this reacts with the refrigerant to produce hydrofluoric acid, which makes the system acidic and also it becomes an electrolyte. This in turn causes electrolytic deposition of copper from the system pipework onto the steel face of the shaft seal (and ay other hot running parts), and this prevents the seal from starting properly.
The likes of Kwik Fit, et al, who openly advertise a re-gas service for your car may not spend as much time looking for a leak and indeed resolving a leak as they should.
This electrolytic deposition process will also occur within other parts of a compressor, particularly the valves and piston rings, but importantly for a sealed system with a hermetically sealed compressor so with no shaft seal the deposition effect does not lead to increased leakage. But no point at all in adding gas to a system that has lost its gas until the reason for the loss is established and resolved.
The cowboy method of purging the system with gas to remove the air, rather than vacuum dehydrate, might be the norm in certain places or by certain engineers, but Triggers' who practice this way are not doing you any favours, so if you see one doing this, next time you use him make sure you provide him somewhere to tie up his horse.
Likelihood is if Trigger can't be bothered to evacuate properly, he won't be bothered to pressure test and leak find properly either.
The likes of Kwik Fit, et al, who openly advertise a re-gas service for your car may not spend as much time looking for a leak and indeed resolving a leak as they should.
This electrolytic deposition process will also occur within other parts of a compressor, particularly the valves and piston rings, but importantly for a sealed system with a hermetically sealed compressor so with no shaft seal the deposition effect does not lead to increased leakage. But no point at all in adding gas to a system that has lost its gas until the reason for the loss is established and resolved.
The cowboy method of purging the system with gas to remove the air, rather than vacuum dehydrate, might be the norm in certain places or by certain engineers, but Triggers' who practice this way are not doing you any favours, so if you see one doing this, next time you use him make sure you provide him somewhere to tie up his horse.
Likelihood is if Trigger can't be bothered to evacuate properly, he won't be bothered to pressure test and leak find properly either.
RichardS
N/A
The EZChill cylinder I bought in Halfords some years ago is 530ml so plenty of R134A for several top-ups or a big fill. I only use it for top-ups and have done 3 vehicles so far with this cylinder. Cost me £30-ish if I recall correctly.
Richard
Heckler
Well-Known Member
Methinks you protest too much, you dont do yourself any favours being sarcastic! Some of us have worked in this game as well you know and your explanation of what happens to the seals in car compressors isnt strictly true. The American car industry used to advise owners to run their AC on a regular basis to "lubricate" the seal.
Calling people Trigger is pretty stupid, do you think you are the only hoss in town?
Heckler
Well-Known Member
The EZChill cylinder I bought in Halfords some years ago is 530ml so plenty of R134A for several top-ups or a big fill. I only use it for top-ups and have done 3 vehicles so far with this cylinder. Cost me £30-ish if I recall correctly.
Richard
Doing as we do sensibly, avoids paying self professed Experts for something the average handyman can do quite easily!
KAM
Well-Known Member
Thanks for the info. It confirms my suspicion that oil loss from a marine system with a hermetic compressor is likely to be a lot less than an automotive system and that it would be unwise to use an automotive top up kit containing oil. It seems that leakage from a non domestic system particularly the two part systems with compressor and cool box with field assembled joints such as self sealing couplings and schrader valves could be up to 10% per year. My system is 8 years old so its not unreasonable that it needs a top. Its probably worth doing a leak check on the joints and valves every few years but not sure that easily available leak detection fluid would be sufficiently sensitive with a threshold of about 100 grammes per year.
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PaulRainbow
Well-Known Member
The truth is this, car air-con systems running R12 never needed re-filling unless they had a physical fault that caused a leak, like a cracked hose etc. All car air-con systems running on R134a will lose refrigerant, due to the fact that the R134 molecule is so small (smaller than R12 molecules) the seals cannot contain it. It has nothing to do with bad practice or moisture being allowed into the system. If it was down to that, the only cars that would need periodic re-filling do to leaks would be those that had already had work done on them, and that work would need to have been done badly. It's a fact that all cars will need re-filling at some point or other, from new. Claiming this is down to bad practice would mean that every manufacture would be fitting systems incorrectly in every single car that comes off the line, it simply isn't true.
Automotive air-con will have pressure switches for high and low pressure, if the system exceeds or falls below set parameters the compressor clutch (electrically operated) will be disengaged. So, when the system has lost a relatively small amount of refrigerant the pressure will drop, the clutch will disengage and the air-con will be inoperative. So, if a small quantity of refrigerant is added back to the system it will work again, care would need to be taken not to add too much though. An experienced air-con technician, worth his wages, would be able to easily tell whether there was a leak caused by a fault, or if it was the usual low refrigerant level caused by expected losses, as soon as he connected his equipment. It is not rocket science to add a little refrigerant and run the system, topping it up to an appropriate pressure. There really isn't a cowboy issue here, if the guy knows what he's doing he'll understand the pressures involved before he starts and what they should be when he's finished. He won't be adding refrigerant to a system that has zero pressure in it, that indicates a leak due to a fault or a system that's been inoperative for a very long time.
However, best practice for a professional air-con "technician" would dictate that a full evacuation is carried out, followed by a leak test and refilling with the exact amount of refrigerant as specified by the manufacturer. This is also not rocket science and does not waste the refrigerant that was left in a system. F gas compliant equipment has to be capable of recovering the refrigerant in the system and this is re-usable. So, your system holds 600g and only has 300g in it, you could squirt some Halfords stuff into and take a best guess (you should be able to get it close enough to work), you could get an experiences tech to add an approx amount (he should get it very close, unless he's a tosser) Or you can get the tech to be a bit more thorough.
Being thorough means sucking all of the refrigerant out of the system using a vacuum pump, into a vessel that will weigh what goes into it. So, you know you sucked 300g from the system. You leave the pump running for a while, making sure everything has been removed, and you close the service valves. You then leave it for a while and keep an eye on the vacuum. If the vacuum remains unchanged you know there is no abnormal leak, so you refill with 600g of refrigerant. Job done !! In the real World, if the guy has some half decent equipment, he'll program it it and go do something useful, like read the PBO forum, whilst the equipment does all the work. He'll know how much refrigerant was used, the difference between what came out and the correct amount, unless he's a crook he'll charge you accordingly.
As for boat fridges, a system that is truly sealed will have silver soldered joints and will only need re-gassing in the event of a fault induced leak (cracked pipe etc). Many boat fridges were assembled from kits and contain quick fit pipe connections, these feature seals and suffer the same fate as car air-con systems.
Automotive air-con will have pressure switches for high and low pressure, if the system exceeds or falls below set parameters the compressor clutch (electrically operated) will be disengaged. So, when the system has lost a relatively small amount of refrigerant the pressure will drop, the clutch will disengage and the air-con will be inoperative. So, if a small quantity of refrigerant is added back to the system it will work again, care would need to be taken not to add too much though. An experienced air-con technician, worth his wages, would be able to easily tell whether there was a leak caused by a fault, or if it was the usual low refrigerant level caused by expected losses, as soon as he connected his equipment. It is not rocket science to add a little refrigerant and run the system, topping it up to an appropriate pressure. There really isn't a cowboy issue here, if the guy knows what he's doing he'll understand the pressures involved before he starts and what they should be when he's finished. He won't be adding refrigerant to a system that has zero pressure in it, that indicates a leak due to a fault or a system that's been inoperative for a very long time.
However, best practice for a professional air-con "technician" would dictate that a full evacuation is carried out, followed by a leak test and refilling with the exact amount of refrigerant as specified by the manufacturer. This is also not rocket science and does not waste the refrigerant that was left in a system. F gas compliant equipment has to be capable of recovering the refrigerant in the system and this is re-usable. So, your system holds 600g and only has 300g in it, you could squirt some Halfords stuff into and take a best guess (you should be able to get it close enough to work), you could get an experiences tech to add an approx amount (he should get it very close, unless he's a tosser) Or you can get the tech to be a bit more thorough.
Being thorough means sucking all of the refrigerant out of the system using a vacuum pump, into a vessel that will weigh what goes into it. So, you know you sucked 300g from the system. You leave the pump running for a while, making sure everything has been removed, and you close the service valves. You then leave it for a while and keep an eye on the vacuum. If the vacuum remains unchanged you know there is no abnormal leak, so you refill with 600g of refrigerant. Job done !! In the real World, if the guy has some half decent equipment, he'll program it it and go do something useful, like read the PBO forum, whilst the equipment does all the work. He'll know how much refrigerant was used, the difference between what came out and the correct amount, unless he's a crook he'll charge you accordingly.
As for boat fridges, a system that is truly sealed will have silver soldered joints and will only need re-gassing in the event of a fault induced leak (cracked pipe etc). Many boat fridges were assembled from kits and contain quick fit pipe connections, these feature seals and suffer the same fate as car air-con systems.
vyv_cox
Well-Known Member
On Paul's last paragraph, it seems these DIY self assembly joints will be phased out, brazed systems only in future apparently.
superheat6k
Well-Known Member
I'm out of here.
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dom
Well-Known Member
Fair enough, but having met you in Cowes year before last, I can honestly say that I have never spoken to anyone with such a knowledge of refrigeration systems. Wld be a shame to see true professional expertise sidelined in favour of heartfelt hearsay.
Heckler
Well-Known Member
No hearsay from here. It used to be part of my game in the oilfield. Mostly R12 and R22. Also be aware, sorry Paul R, but the car compressors did leak, the manufacturers did advise to run every so often to "lube" the seals. They were face to face seals and anyone who didnt have the proper tool to take off the electric clutch would inevitably break them.
The Halfords top up cans are fine used wisely.
PaulRainbow
Well-Known Member
No need to apologise Stu, i didn't say they didn't leak
One of my points was that car air-con systems will lose refrigerant from new, not because of dodgy workmanship, but because of the size of the R143 molecule.
superheat6k
Well-Known Member
Thanks to the support Dom has offered - I will return to add some balance here.
The industry has moved on since the good old days of R12, R22 and times when venting systems for maintenance was perfectly normal, and indeed legal. R12, the original 'Freon', became the base rating assigned for CFC pollution, and was made illegal to charge into systems in 1995, along with deliberately venting to atmosphere. The R134a molecule being smaller than R12 and hence more leaky is another myth, that came along around the same time. R134a has been the base of most large usage refrigerants since R22 demise and the partial leak theory has been debunked, indeed if anything it is the higher pressure components such as R32 and R125 used in gases such as R407C that will leak first. There is a case that dry seals will leak, but so will electrolytic copper plating cause seals to leak and not get better. A dry seal should stop leaking once it has regained lubrication, a copper plated seal face won't re-seal.
And yes I will and do object to venting and failure to properly pressure test and evacuate systems. If boaters on here are paying a professional to undertake work on their boat's systems it is not unreasonable they should have the work done properly. De bunking the black magic of refrigeration and providing a simple understanding of what processes should be normal for someone undertaking service and repair works is the sort of knowledge non techie users of the forum should have available and properly explained.
PaulRainbow
Well-Known Member
It's a really good myth, the whole World believes it, except you. What evidence can you provide to support this claim ?
sarabande
Well-Known Member
There is a difference in the molecular weights according to Wiki:-
R134a 102.03 g/mol
R12 120.91 g/mol
Engineering Toolbox has fuller details:-
https://www.engineeringtoolbox.com/dichlorodifluoromethane-R-12-d_972.html
and
https://www.engineeringtoolbox.com/r134a-properties-d_1682.html
Now all that means little to me, apart from a passing understanding of what appear to be quite different physical properties of R12 and R134a.
What does concern me is the apparently cavalier approach of a couple of the forum mechanical practitioners in advocating re-filling practices which are at best inefficient, and at worst illegal and environmentally unacceptable.
There are presumably very good technical and compliance reasons why proper refrigeration engineers have to be licensed, and their use of the gases tracked. Shade tree mechanic practices following some of the dubious (but physically possible) charge/change procedures outlined in car forums should not be part of our boating environment.
We should appreciate and encourage the forums' engineers in all disciplines for the value they add to boating knowledge, and for the time they spend making positive posts to help other members. Without their input, the forums would be far less interesting and far less of a rich technical resource.
R134a 102.03 g/mol
R12 120.91 g/mol
Engineering Toolbox has fuller details:-
https://www.engineeringtoolbox.com/dichlorodifluoromethane-R-12-d_972.html
and
https://www.engineeringtoolbox.com/r134a-properties-d_1682.html
Now all that means little to me, apart from a passing understanding of what appear to be quite different physical properties of R12 and R134a.
What does concern me is the apparently cavalier approach of a couple of the forum mechanical practitioners in advocating re-filling practices which are at best inefficient, and at worst illegal and environmentally unacceptable.
There are presumably very good technical and compliance reasons why proper refrigeration engineers have to be licensed, and their use of the gases tracked. Shade tree mechanic practices following some of the dubious (but physically possible) charge/change procedures outlined in car forums should not be part of our boating environment.
We should appreciate and encourage the forums' engineers in all disciplines for the value they add to boating knowledge, and for the time they spend making positive posts to help other members. Without their input, the forums would be far less interesting and far less of a rich technical resource.
superheat6k
Well-Known Member
See below
But also, direct experience of working with this refrigerant fluid since its inception in 1993 (that's 25 years) and on systems just a tad larger than the average boat fridge. My company also works on development projects with Chemours (formerly Du Pont).
Molecular leakage is certainly not mentioned in the notes surrounding the two F Gas Directives, which primarily means as far as refrigeration is concerned R134a and R125, which are extensive (NB all R400 series are blends of other R number refrigerants).
Believe me at £60 / kg no leaks are acceptable especially on systems that may hold up to 700 kg of the stuff.
The myth arose because at the time R134a was introduced at some 5 times the price of R12, leaks, which were then commonplace and cheap to fix, had to be resolved, and many system leaks occurred due to collapse of mineral oil impregnated O seals when POE grade oils required for HFC refrigerants were introduced.
To close my statement with this study of R134a leakage in large commercial vehicles - nowhere does it mention molecular size with reference to R12 as an issue of concern or cause of leakage - plenty of other reasons however.
https://www.arb.ca.gov/research/seminars/baker3/baker3.pdf
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PaulRainbow
Well-Known Member
I don't think it is safe to draw too many parallels between the industrial systems that you work on and automotive air-con systems. Whereas commercial systems and indeed domestic refrigeration don't generally have quick fit style connections automotive air-con has several on a single installation.
When cars were built with systems running R12 it was unheard of to have to replenish the refrigerant unless there was a physical problem, such as a damaged pipe etc. Since changing to R134a it's well known that the air-con will need periodic servicing and re-charging. I'm talking of systems that were filled with either R12 or R134a from new, not retrofitted systems.
owen-cox
Well-Known Member
Paul, You should never use a vacuum to check of there is a leak on a system. dry nitrogen pressure testing is the only way to be sure and also does you the favour of drying the system further. At the end of the day you can only get 1 bar of vacuum on a system maximum and its much easier to get say 10 bar on a fridge system with nitrogen which will make it substantially easier to find a leak and prove there isn't one by using nitrogen as it is a non condensable gas and will only change slightly with temperature. I always do it this way. I wont ever guarantee a marine fridge system against leakage if it has quick connectors in it ad always cut them out and braze the joints to be able to guarantee against gas loss.
