How much 134a to put in?

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How much 134a to put in?

Postby booster » Sun Aug 28, 2005 10:10 pm

I have a Robinair vac and auto charging system. The a/c system on my car requires 30 oz of 134a. The charging system charges in pounds. How many pounds of 134a is required to get 30 oz? Does 16 oz = 1 lb in this case?

Thanks,
Jeff
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Ounces and pounds

Postby Tom Greenleaf » Sun Aug 28, 2005 11:22 pm

Interesting question. As we know water is a pint a pound the world round, and refrigerant is probably less. I'm guessing but I think it's close.

You didn't mention the vehicle but most have stickers that are underhood and go by weight. Suggest you add 3/4 by weight and watch the pressures. You can always add a bit more.

I'll be watching this post and am embarrassed that I don't know the exact answer for you. I'll be watching, Tom
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Postby Duane in Japan » Tue Aug 30, 2005 9:13 am

An ounce is an ounce is an ounce, although an ounce of water may take up more space than an ounce of R134a. Your machine will do the measuring for you, yes 16 oz of freon gas will equal one pound of freon gas. Although it may take up more space than a pound of water is neither here nor there. What weighs more, a ton of bricks or a ton of feathers. I am sure a ton of feathers will fill a 40 foot trailer while a ton of bricks may fit in the trunk of your car.
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Postby Duane in Japan » Wed Aug 31, 2005 1:22 pm

Tom and all mathameticians,

I will stick with my original post, the machine will weigh this gas as it is designed to weigh R134a by the ounce or pound, if we used a scale and a 30lb bottle of R134a and serviced 30oz (1lb 14oz) of gas by weight then the job would also be correct. I just heard from an old hand this week that back in the 80's he use to turn the big bottle upside down and fill a graduated cylinder full of liquid up to the 30oz mark, turn the bottle valve completely closed then continue to allow the system to suck the graduated cylinder dry and you knew that you had serviced 30oz of R12 back in those days, the graduated cylinder was graduated to accept R12, not to accept water by volume nor by weight at the 30oz mark, just R12.

Just to bump on the retrofitted R12 to R134a you would not service the new R134a to the amount of R12 stated on the sticker or in the book, it will be in the 80% plus range, about 24oz (R134a) in a 30oz (R12) system, does this mean that R12 and R134a weigh the same, NO, I dont even know each weight by volume to be honest but I would not service by weight in a retrofitted system, 80% is a starting point and watching vent temps will be my ultimate goal when I cant get it any colder, yes this takes time, sometimes too much time as I am a little anal at times.

In this thread we are comparing apples to apples it seems, so lets just let the machine do its job according to the sticker of 30oz. kewl
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