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Old 2nd June 2020, 10:36   #11
DMGRS
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Also, I've seen cars develop a pinhole leak or a small leak from a seal that has allowed the gas to leak over a couple of years - so a NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD- to detect as it's so small but enough loss to be a royal pain.

Yes, I'm looking at you - my old MG ZS diesel!
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Old 5th June 2020, 20:07   #12
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Our cars if filled with the factory fitted gas can be expected to lose anywhere between 2% to 10% by weight per year. 35% you have a leek somewhere not just in the veg patch.
The new gas used in all new cars does not mix well with the old CFC gas used in our cars. Most Garages today check AC on a vacuumed check machine all your gas is sucked out and the system test is carried out under vacuum. If the system holds the vacuum the machine fills the system back up with new gas to a given pressure. Not by weight. Good A/C guys are hard to find these days the machines are taking over.
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Old 5th June 2020, 21:10   #13
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Originally Posted by alanaslan View Post
... the machine fills the system back up with new gas to a given pressure. Not by weight.

What makes you think that Alan?

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Old 5th June 2020, 22:26   #14
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What makes you think that Alan?



Simon
Agreed, there has to be a quantity, as almost any amount of gas could.be filled (along with appropriate oil) to a given pressure,surely?

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Old 5th June 2020, 22:49   #15
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Most of the machines I have seen vacuum out to a waste tank then fill a standard amount of oil with the new type gas on a pressure stop valve. As the original gas has a different mass to that of the new gas. The cars fill label is of no use.
You can only fit a gives mass of gas in a system at a set pressure.
It all has to do with STP and not the engine oil additive.
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Old 6th June 2020, 06:50   #16
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Any machine I’ve encountered has a scale that the bottle sits on.
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Old 6th June 2020, 08:17   #17
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As the original gas has a different mass to that of the new gas.
Hi Alan,

I'm assuming that by "original" you mean R134a and by "new" you mean R1234yf.

I've done a quick search and it's said that R1234yf is a "drop in" replacement for R134a, meaning that no changes are necessary. It may be that a minor adjustment is made to the charge but I believe that it will still be determined by weight. As SWorks says, the automatic machines contain a bottle of refrigerant sitting on a set of scales which isn't visible to the observer.

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Old 6th June 2020, 13:58   #18
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Hi Alan,

I'm assuming that by "original" you mean R134a and by "new" you mean R1234yf.

I've done a quick search and it's said that R1234yf is a "drop in" replacement for R134a, meaning that no changes are necessary. It may be that a minor adjustment is made to the charge but I believe that it will still be determined by weight. As SWorks says, the automatic machines contain a bottle of refrigerant sitting on a set of scales which isn't visible to the observer.

Simon
The later R1234yf isn’t compatible with the earlier R134a systems and the pipe connections are different so you can’t connect to the machine. The machine I use has two bottles, a larger one for R134a and a smaller one for R1234yf and both sit on scales. There is one high and one low pressure pipe with quick release connectors to change the connectors to the appropriate system. If you go from one gas to the other the machine carries out an internal cleaning process. If R134a became obsolete could you vacuum the system and add R1234yf via the R134a connectors? I’m not sure, possibly........
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Old 6th June 2020, 20:26   #19
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Originally Posted by SD1too View Post
Hi Alan,

I'm assuming that by "original" you mean R134a and by "new" you mean R1234yf.

I've done a quick search and it's said that R1234yf is a "drop in" replacement for R134a, meaning that no changes are necessary. It may be that a minor adjustment is made to the charge but I believe that it will still be determined by weight. As SWorks says, the automatic machines contain a bottle of refrigerant sitting on a set of scales which isn't visible to the observer.

Simon

I guess you could drop in apples to the oranges. However I have no idea what you would end up with. The two gases are interchangeable after a nitrogen flush, mixing the two is not a good idea, it’s a total different chemistry. A top range professional system should not even attach to the connectors. Sadly there are many cheep professional looking units that will do anything and fit anything.
A top range unit has a large bottle of old style virgin gas which sits on a digital scale. It also has a smaller bottle of the new style virgin gas, again sitting on a digital scale. The reason that the new style gas bottle is smaller is a system requires less of the new style gas to do the job. This kind of unit also has two recovery vacuum tanks .
Each side of the unit is a dedicated system!

Sadly the theory was the old gas would not be sold after April 2018. But a bit like halon fire extinguishers where no Virgin gas was to be produced or sold after 2006. No country put into place a gas disposal scheme. Also they forgot that the Aircraft industry require Halon as all aircraft must have halon fire fighting systems onboard. Also the gas has to be 98.5% virgin gas minimum.
I guess no aircraft have been built since 2006. OH that’s right they still produce virgin gas. Sadly the children who dream up these wonderful ideas to save the planet, have no understanding or experience of the real world.

The result of the plans to ban old style gas production and its sale meant that in the lead up to Hydrocarbon day the Chinese built thousands of A/C degas / regas machines that were pressure valve controlled, which were sold all over Europe.

I personally can not understand why anybody would think vacuum testing a pressure system would be a good idea. You would never pressure test a boiler by placing it under vacuum. They are tested under hydrolic pressure test then subjected to a steam test under operating conditions. But hey what do I know. Just cos that’s the way they have done it for the last two hundred years does not mean they are correct. Or does it?
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Old 6th June 2020, 21:02   #20
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This just reminded me of an incident in a Scottish town just outside Glasgow about 20 years ago. Swimming pools use a base chemicals to chlorinate their water and an Acid to then bring the Ph of the water back to around 7.2 .
One of the systems uses Sodiumhypochloride and hydrochloric acid. The chemicals are stored onsite in 1200 litre bulk tanks then pumped to 25 or 50 litre day tanks. The bulk tanks have different connectors so you can’t put the wrong chemical in the wrong tank.
Sadly the combination of a new Duty manager, a new Tanker driver, and a box of male, female adaptors and step up and step down adaptors and connectors in the side pod of the tanker, the unthinkable happened.
The duty manager told the tanker where the acid had to be pumped into to fill the bulk tank. The Tanker driver noted the connection was the wrong gender for the line on his tanker. Checked again with the Duty Manager, then raked through the adaptors in the side pod till he found the parts he needed to pump his 1000 litre delivery into the bulk tank.
Seconds after he started to pump his load there was a very strong smell of the baths. He finished his delivery as the swimming pool were having a fire drill.
The building had been evacuated due to a smell of chlorine gas over the next half hour over five thousand people in the surrounding area were evacuated for a period of 26 hours until the poor fire brigade could declare the area safe.
The company delivering the Acid were taken over before the court case and new procedures were put in place.
A fool proof system but not a human proof system.
Alan
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