About to charge r290 ss system

[imprez55]

My ss's transformation from a window ac unit is about complete. I have tested the unit to 250psi of OFN overnight with no fluctuation and am on the 2nd of the triple evac. First two evacs will be at least 500 microns (first was at 430) and the last will be at 250 microns.

The system was originally charged with R22 and used mineral oil so I am not worried about the switch to R290 (BBQ grade unfortunately). My plan is to charge to around 50psi and tune according to superheat from there (7.5 feet of .028 captube btw).

My questions are:
1) If I recall correctly R290 can be charged either liquid or vapor, I just want to make sure this is correct as I plan to do vapor.

2) What static psi should I start with. I understand static is useless from a tuning standpoint, but a system with R290 needs less refrigerant than, with lets say, R22 so I do not want to overcharge it initially.

3) Should I charge with shoddy BBQ propane, real R290, or just re-charge with R22. Going along with this to cut back costs if possible, I would think 2lbs of refrigerant would be enough, correct?

[[XC] gomeler]

BBQ grade R290 will work fine, your filter/dryer will suck up what little moisture is in the R290. Some BBQ cylinders have valves that won't let them dispense liquid propane, so keep that in mind. I always charge by vapor, no problems so far. Static pressure and total refrigerant charge depend 100% on the system in question. Whatever numbers I would spit out as suggestions would be completely irrelevant. I'd suggest doing just as you said, dumping 50psi into the system and firing it up. For the dummycharge just get the suction line close to 5" Hg with no load and then begin charging via superheat with a load on the evap.

[SexyMF]

I start from a static charge of 100PSI. Even then I don't get frost until 150PSI.

[Postal Dude]

If you want to keep your unit's filter drier in tip top condition, run the gas thru a filter as its charging.

A 3.7Kg BBQ propane is pretty cheap and will sort you out

[SexyMF]

I use the Bernzomatic propane cylinders with a home-made adaptor (like so many others). Not the cheapest option, but you get a few charges out of one cylinder.

[Postal Dude]

SexyMF can you post or pm me a small guide on how to produce such an adapter? cheers

[runmc]

I would do it just as you said (50psi static) vapor. Sounds like you did your homework. :)

Benzomatic propane with a home-made adapter is a good idea too.

[tiborrr]

Anyone though about using the Wigam Maxygas fuel as a refrigerant. As stated on the label it includes:

- butane
- propane
- propylene
- acetone

I know acetone is mixed in the gas to stabilize it, but what would acetone do to a system if one would charge it with it? Could be a very cheap portion for a auto-cascade blend... What do you think?

[trance565]

depending on how much acetone there is, it would eat away at the seals on your valve stems/ access points. buuut it probably isn't concentrated enough for that.(in any reasonable amount of time atleast)

[EliTE22]

My ss's transformation from a window ac unit is about complete. I have tested the unit to 250psi of OFN overnight with no fluctuation and am on the 2nd of the triple evac. First two evacs will be at least 500 microns (first was at 430) and the last will be at 250 microns.

The system was originally charged with R22 and used mineral oil so I am not worried about the switch to R290 (BBQ grade unfortunately). My plan is to charge to around 50psi and tune according to superheat from there (7.5 feet of .028 captube btw).

My questions are:
1) If I recall correctly R290 can be charged either liquid or vapor, I just want to make sure this is correct as I plan to do vapor.

2) What static psi should I start with. I understand static is useless from a tuning standpoint, but a system with R290 needs less refrigerant than, with lets say, R22 so I do not want to overcharge it initially.

3) Should I charge with shoddy BBQ propane, real R290, or just re-charge with R22. Going along with this to cut back costs if possible, I would think 2lbs of refrigerant would be enough, correct?
flip the propane tank up side down when charging, works much better, u never know what other gas r in the tanks also, ive alway had troubles charging with bbq propane unless the tanks inverted, helps a lot:up:

[EliTE22]

I start from a static charge of 100PSI. Even then I don't get frost until 150PSI.

did u charge with liquid or vapor?

[imprez55]

SexyMF, I would also like some more info on your adapter. My initial adapter did not hold up to the pressure test I made for it before I went to charge, so the system is still empty. One other question for you, from what I have read propane is at 110psi at room temp, so did you charge by liquid?

I was thinking either using one of the spare Benzomatic propane tanks or use one of the normal size tanks and just cut an extension hose and use a hose clamp to hold a schrader (I don't know how well that will hold up to pressure either though).

tiborrr: does it give percentages or anything of the gasses in it? The other gasses might be too small of a concentration to do any real good if you are planing it as a premixed blend. They also might vary to make the batch the cheapest they can at that point.

[SexyMF]

You (well - I) don't charge R290 by liquid. This is charged as vapour via the suction line. Sorry, I cant give pictures of my adapter at the moment, my gear is elsewhere. But, it is just a cheap Bernzomatic torch head with the end chopped off and a schraeder valve brazed on. I use a 'T' setup on with charging hoses with valves so I can shut off the vacuum pump and/or the propane bottle.


I have read propane is at 110psi at room temp

Not to sound trite - but everyones room temperature is different. On a new bottle I think I can get 100PSI straight from the bottle. But as you draw it off during the charge it freezes (of course), so I tend to use a tub of warm water to help keep pressure coming from the cylinder.


I am talking about unloaded charge here - just to be clear.

[trance565]

for an adaptor, you can go to a propane store, and they have little nozzles, that will screw into the propane tank, and have a 3/8th inch hole in them, the schrader valve fits in perfectly, so if your trusting in your brazing skills, you can braze em together and have a schrader valve come straight off the propane tank.

[tiborrr]

Thanks trance for your rapid response! :yepp:



tiborrr: does it give percentages or anything of the gasses in it? The other gasses might be too small of a concentration to do any real good if you are planing it as a premixed blend. They also might vary to make the batch the cheapest they can at that point.
No, there are no percentage values given or anything, but I agree with you on the quality of the blend. I guess i'll rather stick to a cooking gas (~ 70% R-290 / ~ 30% R-600a) - 10kg for 17€ - for further auto-cascade testing. Straight R-600 or R-600a is damn expensive.

If I'll find some spare time tommorrow I will show how to make a SAE charging adapter for left-handed thread cooking gas cylinder. It's easy, as trance described in the post above mine.

Best Regards,
Niko :up:

[trance565]

no prob, i know straight acetone will eat thru a soufle cup in about .. 5 seconds, so i honestly wouldnt trust it in any system that's got seals using rubber or plastic. 1-3oz in a 17 gallon tank of gas is alright(improves milage a bit and cleans injectors) but even still, it's only something somone should do once a month at most.

[EliTE22]

You (well - I) don't charge R290 by liquid. This is charged as vapour via the suction line. Sorry, I cant give pictures of my adapter at the moment, my gear is elsewhere. But, it is just a cheap Bernzomatic torch head with the end chopped off and a schraeder valve brazed on. I use a 'T' setup on with charging hoses with valves so I can shut off the vacuum pump and/or the propane bottle.



Not to sound trite - but everyones room temperature is different. On a new bottle I think I can get 100PSI straight from the bottle. But as you draw it off during the charge it freezes (of course), so I tend to use a tub of warm water to help keep pressure coming from the cylinder.


I am talking about unloaded charge here - just to be clear.
not what i might but doesnt matter, i didnt see ( :am: ) u were using Bernzomatic propane cylinders,