R22 to MO 99

[shaun66]

when this conversion is done on a rack, what effect is there on TX valves


I think i know what will happen from literature I have read, but a case manufacturer is telling me different

[icemeister]

Here's a Case History story from DuPont's website:

http://www2.dupont.com/ISCEON/en_US/...igeration.html

[trippintl0]

I have a question after reading that story: How on earth do you charge 2600 pounds of refrigerant into a system. With 87 drums holding 30# each? Does a helicopter fly in a massive tank of refrigerant? I only work on small stuff!

[basshound71]

Is it on the ground or on a roof? Can use 125# or 1000# cylinders

[All-Good]

Total refrigerant MO99 charge was 2600 lbs for the entire store, which was probably 4 racks @ 600-700 lbs each. I have seen it done plenty of times using 110# cylinders.

[All-Good]

when this conversion is done on a rack, what effect is there on TX valves


I think i know what will happen from literature I have read, but a case manufacturer is telling me different

If the valves sizing and operation was good on R-22 there should be no need to change out since the mass flow rates of R-22 and MO99 are very close.

Depending on desired superheat and where it was operating on R22, you may want to make a slight adjustment to individual cases.

[RobY]

The area to watch our for with TXV sizing is if you are running the rack with a lot of sub-cooling. Many of the R-22 replacements will need higher mass flow rates at high sub-cooling values than the R-22 TXV valve can deliver. You may also have problems with distributor nozzles being undersized. In the worst cases you may possibly even have an undersized liquid line exiting the condenser with some alternatives like R-422D. These are some of the reasons why some R-22 alternatives are no longer favored in LT R-22 racks.

The closest match to the mass flow rate of R-22 in low temperature refrigeration is R-407A or R-407F. R-407A also delivers all the capacity the R-22 system had, and is one of the favored options by Copeland.

I have no problem with using R-438A (MO99), I just think it is not as close a match to R-22 as some of the other options. It does have the benefit of working well at high concentrations of mineral oil. Like Dr. Freon said, if you have some spare capacity available on the rack, it will do a good job.


Rob Yost
National Refrigerants

[pecmsg]

Welcome back Rob

[kiwireeferman]

Welcome back Rob

Ditto

Really enjoy reading your comments. Straight forward, to the point and no BS.

[frigeguy]

The area to watch our for with TXV sizing is if you are running the rack with a lot of sub-cooling. Many of the R-22 replacements will need higher mass flow rates at high sub-cooling values than the R-22 TXV valve can deliver. You may also have problems with distributor nozzles being undersized. In the worst cases you may possibly even have an undersized liquid line exiting the condenser with some alternatives like R-422D. These are some of the reasons why some R-22 alternatives are no longer favored in LT R-22 racks.

The closest match to the mass flow rate of R-22 in low temperature refrigeration is R-407A or R-407F. R-407A also delivers all the capacity the R-22 system had, and is one of the favored options by Copeland.

I have no problem with using R-438A (MO99), I just think it is not as close a match to R-22 as some of the other options. It does have the benefit of working well at high concentrations of mineral oil. Like Dr. Freon said, if you have some spare capacity available on the rack, it will do a good job.


Rob Yost
National Refrigerants

Hi Rob ..I'm looking at new scrolls with 407 duel temp rack question is what type of discharge pressures should I run? currently (fan control at 190) ( hold back at 180 ) we have a receiver. This seems to work fine at this point.
We have subcooler on LT liquid feed at 50f . Outdoor ambiant 84f daytime and 60f overnight currently.

I just noticed the age of this post....anyone feel free to comment.