Is Ethane / Propane necessary with R-508B in low stage of refrigeration system?

Propane / Ethane is added to refrigerant to improve the refrigerant's solubility in the lubricant
If you haven't already added it and your system requires it, then it is a good idea to do so, since it would improve the refrigeration system's performance

Above stated fact is very correct but that is not reason for not able to reach low temp.... possibiliy ur refrigerant is contaminated or high stage side enough cooling is absent or there is some problem in compressor loading and its control due to which u r not able to get set pt. also ensure static pressure in system is as recommended

One thing to check or simply replace because it easy and inexpensive if the system is open is filter driers and cap tubes. It's pretty hard to identify a slightly restricted cap tube (if it is a cap tube system. I also purchase the refrigerant from the manufacturer. They sell the refrigerant with the small ammount of ethane allready in the cylinder. The particular manufacturer that I have delt with is SoLow. I can get you more info on contacting them if your interested.

Hello ckartson.

Thank you for sharing your expertise! And right on! Our freezer was assessed by a RAC service contractor and their recommendation was to change the filters and cap tubes of both high and low systems. They would also perform some sort of flushing / chemical cleaning in the refrigerant circuit.

I asked if ethane or propane is needed, they answered, "Do you want your compressor to be damaged?" Meaning they won't be using any additive, only pure R-508B. But based on the posts in this discussion, the additives are needed. So I'm thinking maybe these guys will solve our temp set point problem without the propane or ethane, but in the long run the freezer still needs those additives and the problem will haunt us again after a few months.

Guess what? The refrigerant supplier of our freezer is also So-Low! I was able to contact them and they sent a fax of the original proportion of refrigerants they used. Problem now is where to buy propane or ethane. We already have a 20-lb. tank of R-508B so we only need to buy the additives.

You have described the low stage static pressures and refrigerant types. The low stage system is dependant upon the performance of the high stage refrigerant system as it is the source of cooling for the cascade condenser. Please identify the suction and discharge pressures of both the high and low stage systems along with the high stage refrigerant type. The problem with the cooling may be related to the high stage performance

Hello there! Here are the pressure figures:

High stage (R-404A): Suction pressure is 12" Hg vac., Discharge is 185 psig.

Low stage (R-508B): Suction pressure is 10" Hg vac., Discharge is 300 psig.

Ethane and propane are called sweeping agents in the this application. With out them the refrigeration oil will turn to jelly at the outlet of the capillary tube (metering device), causing restrictions and capacity loss. You must have at least one of them in the refrigerant mix in order for the system to work. All manufacturers have various mixes of refrigerants and sweeping agents based upon their design. It is best that you follow the OEM specifications.

I am also having the same problem (almost) I must replace the compressor on an older SO_LOW and ive been told that i must repalce BOTH compressors if one is bad. Anyhow I cant seem to find ANY 170/508B period... where did you find the 508B as near as I can tell the only source of 170 is in maumbi...INDIA... why would an american company produce such a product when a COMMON problem cannot be fixed. Anyhow ..check to make sure that your high stage has the proper refrigerant pressures for 404A... it is pretty important that you get the EXACT amount in for the low side (30"-30lbs of 170 and 175lbs for 508B) however that being said... pressures arnt a good way to charge a system ...I would be alot more comfortable knowing the WEIGHT to charge.. Ive contacted SO-LOW and thats the only info they could give me.... I have contaced my supplier for a source of 170 if I hear anything back I will repost the answer for questions email me at realmccoy333@hotmail.com

I am not clear as to why you have to replace both compressors as they would be totally independent in a cascade system. I assume that you wish to replace the low stage compressor (the one using the mix of R-508B and R-170). R-508B is a "Dupont" Product, also known as "Suva 95". As for R-170; Google it and you should find local suppliers for ethane. I found my R-290 Propane at my local compressed gas supplier. Note; you must specify scientific/ Medical grade gas. Not cheep!

change your filter dryer, evacuate for several days and charge your system as per manufactures specs.

Good Luck

Icarus,

The manufacturer of SoLo Ultra Lo recommends replacement of both compressors. They have changed compressor brands and types. They have a good tech support dept. and have always recommended this. They also provide static charge info for the low stage and weighed charge for the high stage. They als have provided me with refrigerant pre mixed with ethane. I only service these systems once every few years so I rely on the manufacturer for their parts and procedures.

Hello Jacobo. i has been foxing Ultra Low temperature since 1980, and I have had many problems, but no one of them has been unsolved.

Regarding your problem, you have miss the brand name of your instrument, this is very important because we always can talk to the factory.

You have had many instructions and opinions, and may be you start to get confused, well, all you have to do is:

If the low stage compressor is working, Check the oil state and the oil level, if the oil is a Little dark, Take the compressor, Oil separator, and filter dryer out. And separate the low side from the high side, Clean both sides, low and high with a solvent, we call it in Venezuela dielectric solvent. And push the solvent with R 404 or any oder cheaper gas un till no solvent is coming out of the capillary tube. Is very important that this flush is made counter the normal gas flow.

When both sides are clean (Low side and High Side of the same unit) then and only then, install a new compressor, new oil separator and new filter dryer. Make a leak check and finally make a triple evacuation, with an overnight final vacuum and charge the instrument as indicated on the ID. tag. If you do not follow this procedure you will have problems many times......

Please excuse my English but it is not my maternal language..

E-mail: luishenao2000@gmail.com

Best regards.

Luis Henao