Hydrocarbon in R134a system.... 1/3 Charge and 1/2 Charge of R134a?

Hello Engineers.

For the drop-in hydrocarbon replacements for R134a systems (Auto A/C) that are 50/50% R600a and R290 the charge should be half, but on most documentation I read that the recommended charge is only 1/3, mentioning because of the superior ability to reject heat that only 1/3 is needed.

I'm wondering what would be the consequences if 1/2 charge is added (e.g 500g hydrocarbons where 1000g R134a is specified), instead of 300g of hydrocarbons.

Would the system cool better and be more efficient? more liquid avaliable to the TX valve at all times?

Is there more reasons why 1/3 of charge in hydrocarbons of the original r134a charge is recommended instead of half?

Thanks.

Why not just put R134a back in? Its what its designed to run on.

Puttinng more refrigerant in than the system needs will lead to excessive wear and tear and poor performance.
If its a txv system, will your new mix match R134a so the valve can maintain correct superheat?
If the system is a fixed orifice system and you overcharge it you risk slugging the compressor, the orifice would have been sized for a specific pressure ratio and flow with specific refrigerant viscosity.
These things are not simple, though they often apear so when well designed and working to spec.

Hi,

The pressure temp relationship between the HC gas and 134a is pretty similar, i've seen it been used in 134a systems for a long time without any problems, but the manufacturers seem to reccomend 1/3 of the charge stating that it rejects heat well and saying 1/2 is not needed.

In theory 1/2 charge of original r134a reccomendation is what you should put e.g the Hydrocarbon has 50/50 mix of R600/r290 is 0.5kg per liter where r134a is about 1kg per liter, but most manufacturers of hydrocarbons for drop in reccomend 33% of original r134a spec instead of 50%, i was just wondering that, and what would happen if you put more in.... would you just have diminishing returns and be wasting gas?

Quote:

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Originally Posted by Z2TT

Hi,

The pressure temp relationship between the HC gas and 134a is pretty similar, i've seen it been used in 134a systems for a long time without any problems, but the manufacturers seem to reccomend 1/3 of the charge stating that it rejects heat well and saying 1/2 is not needed.

In theory 1/2 charge of original r134a reccomendation is what you should put e.g the Hydrocarbon has 50/50 mix of R600/r290 is 0.5kg per liter where r134a is about 1kg per liter, but most manufacturers of hydrocarbons for drop in reccomend 33% of original r134a spec instead of 50%, i was just wondering that, and what would happen if you put more in.... would you just have diminishing returns and be wasting gas?

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I have to ask first, are you able to get your hands on refrigeration hydrocarbons as i cannot. In Queensland, we are unable to source product. It is obviously not illegal however Australia is so far behind Europe that i have to learn about it on this forum. Just for interest sake, i do have full qualifications so vehicle a/c is within my work scope and vehicle a/c suppy stores still know zero regarding hydrocarbons..mike:)

Pretty sure Bursons sells it in QLD, Hychill brand. On Hychills website they are listed as the QLD distributor

Quote:

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Originally Posted by Z2TT

Pretty sure Bursons sells it in QLD, Hychill brand. On Hychills website they are listed as the QLD distributor

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I didn't know that but will look into it. Currently there is no info available from the Australian governing body,(ARCTIC), though r290 refrigeration equipment is here. I remember some years ago, Western Australia was allowed to use ER12 for vehicles but was illegal in Queensland due to its hydrocarbon properties. Then it disappeared from shelves and hasn't been heard of since... mike.

Hi,

I thought HC 50/50 mix of R290 and R600, when dropping into R134a system the charge should be half, reason being.

The molecular mass of R290 is 44 and for R600, 58.
So halving 44 is 22. And halving 58 is 29 since it's a 50/50 mix of each

So 22 + 29 is = 51 for Hydrocarbon (R290/R600)

And the molecular mass for R134a is 102.

So I was wondering then shouldn't 1/2 the charge in grams be used as R134a when charging with HC?
That's why I'm confused why 1/3 is recommended.

I'm not sure if my reasoning is correct or not but I'm taking it going by that 50/50 mix of R290/R600 is half the mass per given volume of R134a?

So i'm wondering where this 30% of original r134a mass recommendation is coming from, there must be a reason
but I'm not sure what it is, all hydrocarbon manufacturers seem to recommend 30%.