R422D Oil return problems !

[kfjoe]

Hi all

Just wondered if anyone could help
I am having oil return problems on a number of systems that have been converted from R22 to R442D
The oil isnt returning , and on at least one of the systems you can see the oil in the sight glass reciever
Am using Mineral with 422D

Anyone else had any problems or any advice greatly appreciated

Thanks

[nike123]

Hi all

Just wondered if anyone could help
I am having oil return problems on a number of systems that have been converted from R22 to R442D
The oil isnt returning , and on at least one of the systems you can see the oil in the sight glass reciever
Am using Mineral with 422D

Anyone else had any problems or any advice greatly appreciated

Thanks

Do you using it in direct expansion water chillers?

[Noori]

Dear kfjoe.
please write more information about the function and operation for each system u have.
Noori

[albionharley]

Hi -pm me with your email address and i'll send you a pdf that may be of some use.

[kfjoe]

They are DX systems , single compressor cold stores mainly, minus 20 ish room temps
some with hot gas defrost some reverse cycle


thanks

[nike123]

They are DX systems , single compressor cold stores mainly, minus 20 ish room temps
some with hot gas defrost some reverse cycle


thanks

Then you should use R422A (Isceon MO79)
Check this guide.

[Noori]

Dear Kfjoe

I think your problem in the piping system lay out not in the oil type so please send me the piping daigram as soon as u can.

[nike123]

Dear Kfjoe

I think your problem in the piping system lay out not in the oil type so please send me the piping daigram as soon as u can.

Noori, R422D is drop-in replacement for R22 in high and medium temperature applications and it is not suitable for low temperature applications.

For low and medium temperature applications (which are ones that OP have) it is designed other R22 replacement drop in refrigerant named R422A (Isceon MO79).

Check that link in my previous post.
Also, this is retrofit guide for R422A. If oil still dont return aceptably after change of refrigerant, then he should replace some mineral oil with POE. All is explained in that guide.

[kfjoe]

Thanks all
However the information i have says 422D is suitable for medium and low temp , so im confused.
have also tried adding a small amount of poe oil , but still having problems with oil return .

im wondering if velocitys may be lower with this gas ?
as it has problems at low temp/low velocitys
or is it just purely miscibility ?

thanks

[nike123]

Thanks all
However the information i have says 422D is suitable for medium and low temp , so im confused.

Could you post that data or link to them?

[nike123]

Thanks all
However the information i have says 422D is suitable for medium and low temp , so im confused.
have also tried adding a small amount of poe oil , but still having problems with oil return .

im wondering if velocitys may be lower with this gas ?
as it has problems at low temp/low velocitys
or is it just purely miscibility ?

thanks

It is also said in document I posted that it could be used in low temperature refrigeration systems but in parentheses.

Applications

• Medium-temperature commercial and industrial DX refrigeration (can also be used for low temperature):
  
  • Food service
  • Supermarket display cases
  • Food storage and processing
  • Ice machines
  
  
• Residential and commercial air conditioning:
  
  • Best choice for DX water chillers
  
  

But significant is that R422A is declared as suitable for low refrigeration systems:

Applications

• Medium- and low-temperature commercial and industrial direct expansion refrigeration, including:
  
  • food service
  • supermarket display cases
  • food storage and processing
  • ice machines
  
  

So, it appears that R422D is not best solution for low temperature refrigeration.
Anyway, you should read this from R422D retrofit instructions:

7. Monitor oil levels. During initial operation of the system
it is very important to monitor the level of oil in the
compressor (or compressor oil management system)
to verify that oil is returning to the compressor in an
adequate manner.
• If the oil level falls below the minimum allowed level,
top up to the minimum level with the existing oil type.
Do not fill to the maximum level as the level may rise
again.
• Should the oil return appear to be erratic as evidenced
by large swings in oil level during the refrigeration
system cycle it is recommended that some of the oil
be removed from the system and replaced with POE
oil. Replacement of up to 25% of the oil with POE will
help to restore oil return stability. The exact amount
of oil to be changed will depend on the system itself
(evaporating temperatures, physical geometry, etc.)
• POE lubricant should be progressively added to the
system. An initial addition of 10% (of the total oil
charge) should be made. This should be followed by
5% increments until the oil level returns to normal.
• It is important to ensure that, when adding POE oil to
the system, the oil level (immediately after addition)
is kept below the system mid-point (e.g. mid-sight
glass) oil level.
8. Label the system to clearly and permanently show the
refrigerant in the system and any oil(s) present in the
system.

[Howley Racing]

The BIGGEST problem with R422d is its total lack of solubility in mineral oil. This is the reason why there is a 3% content of Butane. The Butane is there for oil return, Butane being a hydro carbon and mineral oil also a hydro carbon, the Butane the solvent, the oil the soluble.

The theory, putting actual numbers aside, is that if your compressor looses 3% oil and the refrigerant returns 3% oil, there is no oil loss from your compressor. However, if your compressor looses 5% oil and the refrigerant still returns 3%, you will loose your oil to the system.

Looking at that 3% Butane content, there can only be so much solubility before it becomes saturated and therefore will not carry any more oil.

Mixing POE oil with mineral oil, in the past has been considered bad by some without real explanation. Dupont recomend the addition of POE oil to aid the return of oil, as you can expect this is the right direction to resolve oil return problems. HFC refrigerants and POE oils are soluble. This leaves the thought about how POE oils and Mineral oils work together. I carried out a small test were i mixed 50% mineral oil and 50% POE oil. At the first instance when the two were poured, they seperated out, but, once they had been shaken and thoroughly mixed, they did not seperate. Apparently the POE oil will pull the mineral oil along with it, and it is this that Dupont base their theroy of adding a percentage POE oil to aid the return.

So, we are now heading in the right direction by adding POE oil to help with the oil return. Good stuff. However, what if you have a good size system that has been operating for years? There is a lot of mineral oil in traps around the system, and if you have liquid receivers, there will be oil in there too. On the site I was involved with there were two chillers with two circuits each circuit was charged with 550kg R422d!! there ware problems right from the start. One of the most memorable was the refrigerant in the sight glass looked like milk. No , not a flashing sight glass, a solid head of liquid that resembled milk. This was the mineral oil! We know the mineral oil is getting backl to the evaperator, but why is it completely avoiding the compressor? To this day We do not know the real answer. The addition of POE seen within an hour oil flooding back to the compressor. It was at this point we took the decision to drop the mineral oil and completely change the oil charge for POE. Since then there have been no oil related problems, after all, its a HFC refrigerant using a POE oil!!.

I had the pleasure of visiting another site that had been converted from R22 to R422d, this time a single chiller with two circuits each with 200kg charge, again the same story. Milky sight glass oil loss and funily enough an oil pump failure. What was interesting on this sight is that it had liquid receivers fitted with a sight glass at the high level point. I coulnd believe what I saw. There was a clear level of oil sitting ontop of the refrigerant!! how will this ever get back to the compressor? Again the mineral oil was dropped and POE oil used where oil return was very quick.

Other things to consider, against Dupont's recomendation of using mineral oil. Take a compressor that is in an outdoor unit. the crank case heater is marginal, where will the refrigerant sit? In the sump of the compressor of course. The heater will be doing all it can to drive off the refrigerant, but in extreme situations, liquid refrigerant will form in the sump of the compressor. Where is the oil pick up on the compressor? At the very bottom of the sump. Compressors do not like being lubricated with liquid refrigerant.

In any normal situation the refrigerant in the compressor isn't too much of a problem as the oil and refrigerant are soluble, R22/ Mineral oil, R134a/ PEO oil. there is always a saturated condition of oil and refrigerant in the sump of the compressor. Not so with R422d and mineral oil!!

It is for this reason that I will refuse to use mineral oil with R422d, and I advise this to anyone I here considering using it. I can only suspect that the same is true for many of these other 'dropin' refrigerants using HFC blends retaining the mineral oil. I have heard reports of compressors failing within weeks of retrofit. Coincidence? I'll let you make your own mind up

[kfjoe]

Thankyou all for your replies on this .

We have noticed exactly what you were talking about Howley racing. a reciever with a high and low level sight glass showing the oil sitting on top of the refrigerant , the oil disapears from the compressor and a large amount can be seen in the reciever.
even after adding a percentage of poe oil , the story is still the same , although in some cases it seems to have helped ,mostly it has not.

now after changing to a full poe charge on one system this has solved the oil return problems ,
but on another different type system we are stll having problems with the poe oil returning to the compressor ,
can still see a level of oil sitting on top of the refrigerant , which i am assuming is the remains of the mineral oil still in the system .
im now wondering if the small amount of mineral oil still in the sysytem my be having a detrimental effect ?

all in all , we have had nothing but problems with 422d , its lower suction pressures and its low range not being as good as r22.

[transcoolchris]

I am seeing the same oil return problems and oil sitting in the reciever and been brought up with the no no of mixing mineral and poe. I can see the logic of adding poe but it is worrying that the mineral oil seems to be seperating. I wonder if R422D is the retrofit answer.

[muddassarusa]

Hi -pm me with your email address and i'll send you a pdf that may be of some use.

if you can send me this file my email address is muddassarusa@yahoo.com please?

[Gibbo]

As R422D is mainly a HFC refrigerant why Dupont thought it would be ok on mineral oil i don't know and as has been stated on large systems it can become a nightmare personally i would steer clear of doing any retrofits using this refrigerant.

[waseem]

Hi -pm me with your email address and i'll send you a pdf that may be of some use.

i need this fdf too
would you please send me too

thanks

my mail : waseemnaamo@yahoo.com

[Fri3Oil System]

Hi All,

you can make R422D work with POE but how much?

If there is an amount of remaining MO in the circuit, like over 3% or 5%, you may have the risk of breaking the compressors, due to a decrease of the lubricity index, if a partial leak occurs.

Then, you obviously have performance losses with these gases. If you clean properly the circuits, you can improve the installation performance, independently of the gas you retrofit to. But, in this case, why go to a more expensive gas, instead of switching to a comodity one, like R407C or R404A?

I will post again our case study that I believe may be of your interest.

www.fri3oilsystem.com/retrofitcase.zip

Regards,

Nando.

[matt p]

Has anyone experienced the same problems with this gas on small a/c units?.

We carried out a retrofit 6 weeks ago to mitsi citi multi on R22 after the previous compressor burnt out.

We changed the compressor and installed a burn out drier on the suction line to catch any acid etc floating around, but our office revived a call on Tuesday saying the compressor had failed again.

Will update once I know more in a couple of hours.

Regards

Matt

[Sandro Baptista]

The problem is also on the service, I mean when the oil is purge from the compressor also a part of hydrocarbon content on the HFC is gone (butane on this case) so less cumulative capability of oil miscibility with the refrigerant. Is the small percent of hydrocarbon on the HFC who is responsible for the oil transportation by be soluble on the refrigerant.

I'm not trying to defend this HFC drop ins...they just are tender...delicate...