DIY - Red Tek conversion

[Farf]

Both Dave(s) are spot on. You can also use a very fine water mist in lieu of fans at the condenser. The condenser doesn't care what fluid you use. The advantage of using water is that you can set (within reason) the head pressure you want to work with. Try the water mist, don't get crazy, just a mist, try to set your head pressure at 190 psig or so.

With your system running you should be able to slowly bleed off refrigerant from the low side with very little oil loss. I doubt you've lost enough oil to be concerned about it at this time. Monitor vent temps while doing this.

Your suction pressure seems a bit low considering your current head pressure and ambient temps. May need to look into that when/if you get comfortable with the charge.

Is the sight glass on your gauges in the center of the manifold? If so, the only time it should "see" refrigerant is when you are charging the system. If it's coming from the high side something is not right.

[fxr]

[Farf]

By the way, what was your total oil charge when you buttoned the system up?
One of the symptoms of an oil overcharge is quoted below.

"Evaporator temperatures and pressures may run low because of the reduced heat transfer from the oil insulating the evaporator tubes."

https://www.achrnews.com/articles/88145-oil-logged-evaporators

If there is lots of oil your head pressures may run higher too.

[dhaavers]

[Farf]

Another thing to check from the linked article from my previous post:

"Low compressor superheat: If the TXV is running low superheat, this will cause the compressor superheat to run lower."

While you are running the system grab hold of the suction line at the compressor is it cold or warm?

[Farf]

Generic Pressure/Enthalpy chart showing the refrigeration cycle.

A bit "techie" but important to understand. Refrigerant flow is CCW.

Basic info that is contained on the HC-12A chart:

HC-12A Pressure/Enthalpy chart with Utahn's high and low pressure (generally) plotted. Unknowns are superheat/subcooling.

HyChill's PH chart matches RedTek perfectly. The area under the curve represents what you see on Redtek's Pressure/Temperature chart. If you know what your superheat and subcooling values are troubleshooting becomes quite simple. In a nut shell a properly plotted PH chart tells you where the refrigerant is and what it's doing (or should be doing) at any point in the system. kind of a sneak peak inside.

This is just information for general consumption. It's pretty rare to have to plot one of these, but I think it's a good visual aid in understanding the refrigeration cycle in terms of pressure and temperature. A lot more info on this via the internet for those who may be interested enough to look further into it.

When I get off my fat A$$ and get around to fixing my A/C I'll plot my system out for you.

[Westaru]

[dlb154]

Anyone use "Kwik Charge" to speed up low side charge?



https://www.amazon.com/Imperial-535-C-Charge-Liqui...FZ7321A1HP

Product claims you invert the can and the device "flashes" the liquid to vapor so you don't damage the compressor.

[Farf]

Your high side gauge does not need to be open to monitor high side pressure and definitely should not be open when charging the system. The pressures you had listed are now suspect. Measure the pressures again with both manifold valves shut. It's good that your head pressure responds well to additional airflow.

Yes, slowly bleed off refrigerant from the low side while the system is running. Don't forget to monitor vent temps. If you get lots of oil coming out with it I would question the amount of oil you have in the system. Based on what Small Car says about the amount of oil needed vs. what you put in needs to be figured out, something not lining up there.

The cold suction line may suggest that you are overfeeding the evaporator. Too much oil in the system as stated earlier is one cause of this. Another cause could be that RedTek is a blend with a 14F temperature glide and your TXV is set for 134A so you may have issues with the superheat adjustment.

Seems like at this point you should concentrate your efforts on finding out what the correct oil charge should be.

Is it possible for you to measure the liquid line temp after the R/D and the suction line temp at the compressor. If so, do not use an IR thermometer. This would tell us a lot about what's going on in the system.

Closing up the engine compartment and the van itself will help with your efforts.

A brief write up on superheat/subcooling and why it's important.

https://www.contractingbusiness.com/service/subcooling-and-superheat-superheroes-system-charging

[Farf]

Should add that if you feel the need to check line temps something like this would work well. You can spend a bit more money and get a thermometer with a pipe clamp type sensor. But I think this one or similar is all you would need.

https://www.amazon.com/Dodolight-Digital-Channel-Thermometer-Thermocouple/dp/B0084JQL1Q

And I should point out that you need to sample the temps on the metal piping in the system and not on the barrier hose itself. You should also insulate the sensor and pipe to ensure accurate measurements.

[RufusRockwell]

Quick detour...
I've been running Red Tek in my 85 tin top and it is a wonderful improvement over the r134. However, I'm getting ready to swap in an EJ22 and will need to evacuate the AC system. What are my options? I've contacted Red Tek but haven't heard back and the local shop won't do it. Can it be safely vented into the atmosphere (far from a flame)???

[Farf]

Vent away...

https://www.epa.gov/snap/final-rule-protection-str...on-and-air

Open the fact sheet PDF you're good to go.

[RufusRockwell]

Thanks!

[Westaru]

[Farf]

Other than the Small Car evaporator being smaller and a marginal bit of hose layout i think your oil charge is probably ok.

Measure the lines with both thermometers and see what you come up with. I'm not sure that the IR gun will give you an accurate enough temperature.

Advantages of using RedTek over 134A. My personal opinion is both are fine to use with the nod going to RedTek. I think the 134A could use an even larger condenser than the upgraded ones people have been installing here. The disadvantage as I see it, is that some have had problems with their TXV's using RedTek.

I have to replace my TXV and have ordered one that the superheat can be adjusted externally without having to open the system. No big hurry on my part as I usually camp/drive above 8000'.

Looking at he chart from RedTek (last line), you can see that the 12A has a much higher latent heat capacity than 134a and R12. To get the same refrigeration capacity as R12 the mass of refrigerant (12A) required, reduces. the same holds true with 134A.

[Farf]

For those of you interested, here's the Sanden (compressor) guide to using super-heat/sub-cooling for charging and troubleshooting. If you are using the RedTek pressure/temperature chart you need to use the bubble point column for super-heat and the dew point column for sub-cooling.

All of the info gathered on the worksheet can them be plotted (if you feel the need) on the PH chart for a visual representation of your system.

Note: I have a minor disagreement on Sanden's subcooling method due to the existence of the Receiver/Drier. This just changes the location of where I would sample temps for sub-cooling.

Once you understand this method, you probably know more about how the system works than most automotive a/c techs.

www.sanden.com/objects/3%20-%20Troubleshooting%20%20-%20Web_01.pdf

[Inlet]

I purchased the Sanden 805 / 6630 compressor, without realizing the connections are #8 and #10, my 84 westy has two equal size threaded connections that are bigger than the #10. I'm soo close to getting this system going again, but now feel like I took two steps back. Are there adapters for this?

[kourt]

Just a note--my SmallCar system runs better on R134 than RedTek, and I am sure it is due to the TXV provided with the SmallCar system, which is designed for R134. I may have to look into the adjustable TXV in the future--I liked the convenience and pricing of RedTek.

kourt

[Farf]

Kourt or anyone interested,

Here's a decent looking TXV that is sized perfectly for the Small Car A/C. Medium temp application and internally equalized. You would need adapters to go from O-ring to flare or if you are still building yours I believe you can go straight from barrier hose to female flare with fittings. Can be used for 134A or RedTek, would need superheat adjusted.

Note: I don't know if it will fit in the area that Small Car allocated for the existing TXV. Edit: I should add that you need access to the valve while the system is running. May not be possible on the SC system.

https://www.ebay.com/itm/Parker-C2FW-3-8X1-2-SAE-T...;rt=nc[/b]

[kourt]

Thanks for that link. I tried RedTek for two years in both my 91 Vanagon and my 87 Volvo 240. Both have all new lines, parallel flow condensers, new evaporators, and new compressors--but the expansion valves were both built for R134. My wife went out of her way to thank me when I switched back to R134 in the Volvo, as it was such an improvement from RedTek.

Part of the problem is we have super hot summers in central Texas. Only so much heat rejection can occur on a 108 degree day like yesterday.

kourt