Retrofiting a R-502 system to R-404a

[apprentice3]

I have a old R-502 reach in that has a bad compressor (locked up). The new copeland K body compressor is set up for use with R-404a refrigerant. The customer also has been trying to get all there 502 systems converted over to the R-404a district wide. When i change this compressor next week, i have heard i need to get all the old mineral oil out to 95%. What kind of things could happen as far as system problems without getting it all out? I am going to change the cap tube while i have the system open to assure i have a new clean cap tube, and also going to add a filter drier. I have heard oil can get trapped in the evap. and lower heat transfer albilities. So i was thinking i would use some of that RX11 flush and flush the evap. and condenser. Is this a good idea? I haven't used RX11 before, is there any problems with it?

One last question kind of off the subject of this.. I have been working at tons of old schools that have all this old equipment that they never will replace only repair. They have a 2000 dollar Not to exceed on every service call on a reach in. My question is that on these old HF2 hobart freezers they all run around 10-20 degrees. They have good pressures, charge is correct by weight, defrost + all fans are working, everything looks good. It seems like it pulls down to 10-20 degrees and just holds it there with it running 24/7. Now some of there new equipment (1980s equip.) maintains at -10-0 degrees. What kind of things could be making these old freezers lose there heat transfer they once had when they were new? What can i do to fix this problem.

[james122964]

This is a reach in, your new compressor has Alkybeneze it mixes with mineral.
I do not think you have to flush the system. You also in do not need to change the cap tube.

Jim

[indy2000]

why 404a instead of r-507?

BTW with 404a you use POE, using a refractometer, you need less than 5% MO in the POE.

Rx11 is very easy to use and is recommended to remove any carbon in the lines and any left over MO. Just spray it in, and purge it out with N2.

[james122964]

why 404a instead of r-507?

BTW with 404a you use POE, using a refractometer, you need less than 5% MO in the POE.

Rx11 is very easy to use and is recommended to remove any carbon in the lines and any left over MO. Just spray it in, and purge it out with N2.

My bad, you are right on the POE.

Jim

[icemeister]

If you convert to R404A you'll need to change the cap tube as it will require a longer length of the same ID.

EDIT: I misread the chart. The cap tube sizing is the same for R502 and R404A.:oops:

Supco Capillary Tube Selection (http://www.supco.com/images/20%20cap%20tubing.pdf)

[apprentice3]

This is a reach in, your new compressor has Alkybeneze it mixes with mineral.
I do not think you have to flush the system. You also in do not need to change the cap tube.

Jim


I gave the supply house the compressor Model number and they gave me a new K body charged with POE oil...


why 404a instead of r-507?

BTW with 404a you use POE, using a refractometer, you need less than 5% MO in the POE.

Rx11 is very easy to use and is recommended to remove any carbon in the lines and any left over MO. Just spray it in, and purge it out with N2.


I have looked at R-507, and i have had mixed reviews. I personnally like it because it is a azeotropic blend, but i have heard some people say it has less capacity than 404a. I am not sure if that is true. I guess the true reason i am not using it is because one, it is not very popular and is hard to come by around here. Two, the school district i am working at wants R-404a in all of there freezers district wide.


If you convert to R404A you'll need to change the cap tube as it will require a longer length of the same ID.


The chart that i have been looking at.. The supco or JB chart for some reason shows R-404a paired up with R-502. It is showing the same size and length. Do you have another chart that shows this? Or do you know exactly how much i should add. My current cap tube size is a .049 @ 120"

[icemeister]

The chart that i have been looking at.. The supco or JB chart for some reason shows R-404a paired up with R-502. It is showing the same size and length. Do you have another chart that shows this? Or do you know exactly how much i should add. My current cap tube size is a .049 @ 120"

:oops: I messed up reading the chart. See my edit.

[bacciagalupe]

why dont you just use 408 refrigerant it is a drop in replacement fot 502 no oil change is needed just change the drier

[james122964]

why dont you just use 408 refrigerant it is a drop in replacement fot 502 no oil change is needed just change the drier

thats what we do.

jim

[Phase Loss]

R-408A contains 47% by weight of R-22, this makes it an in term replacement.

This is most likely why his customer wants to use the long term replacement, R-404A.

[Airmechanical]

i went 502 to hp80 a few times, with no problem no oil change or even nitro purge

these were low temp units

and i did change the TXV's



.

[Phase Loss]

i have heard i need to get all the old mineral oil out to 95%.

What kind of things could happen as far as system problems without getting it all out?

I am going to change the cap tube while i have the system open to assure i have a new clean cap tube, and also going to add a filter drier. I have heard oil can get trapped in the evap. and lower heat transfer albilities.

Back to the OP.

The old rule of thumb is to get the residual mineral oil level to below 5%. But from my understanding, at today's standards...that is quite aggressive.

You may not know it, but you already answered your own question to "What kind of things could happen as far as system problems without getting it all out?"

The high content of residual mineral oil could get trapped in the evap coils and reduce heat transfer.

[bunny]

One problem with POE is that is has some great solvent like properties. If the original R-502 system suffered high discharge temperatures which would have lead to the mineral oil suffering chemical breakdown, you can expect all of that residue to be brought back into circulation by the above mentioned solvent properties of the POE.

So, I'd recommend using an HH type filter-drier, and be prepared to deal with potential comtaminant problems after the conversion.

[bacciagalupe]

hi distrage temp is the problem with all refrigerants latley they seem to costantly block all the capilary tubes latley why cant we all use txv valves in all the systems

[HvacStudentWTI]

just so noone misses the ovious
did you charge 80% r-404a ?
name plate chage of r.502 lets say its 16
so equation would be
16 x .8 = 12.8oz of 404a then u compensate for any extra copper tubeing added to the system for retrofit
1ft = 1/4oz charge i think but its different for gage of pipe i think that ones 3/8 tubeing

[All-Good]

There are other refrigerant options to 404A/507. Like 422A or 422D which can be used with MO. Problem with 404a is residual MO needs to less than 5% or it could log in evap and kill heat transfer. If you do all the flushes and go with > 95% POE, now the POE can lossen debris and end up causing plugages. You have several options.