404A or 134A?

[Mars65]

I went on a w/I and it had. R12 exp valves and someone changed it over to r 408 I always heard and read that r 409 was the freon of choice when dealing with r12 it’s been running like that for 4 years now I believe some of these old semis with the suction line. on the end going through the windings will pump any thing you put in it.its only about 30 years old and went under water in Katrina tiff stuff back in the day

[VTP99]

R408a was a replacement for R502 and yes R409a was for R12 as well as R401a (MP39) , R414b (HotShot) and others.

[pecmsg]

R408a was a replacement for R502 and yes R409a was for R12 as well as R401a (MP39) , R414b (HotShot) and others.

and the a c guys have issues with
410A
NU-23
407A, B , C

[MilfordsMrFixIt]

Sometimes you just never know what the heck is in a system!! The last unmarked one was actually marked, R409a, HotShot, R12, R406a, R416a and a couple others all with magic marker on the wooden support, may as well be unmarked. No dates on any of them either. I removed the 2 HP compressor, dumped out the oil which was pancake syrup color and consistency! The sight glass was black on the 'dot' and all brown inside. I put 20 oz of POE in it, swirled it around a lot, dumped it and filled it with the nameplate called for 48 oz. I added DyeChek and Seal, put the compressor back, replaced the filter dryer and sight, and charged it with R134a. I ALWAYS add a label such as the one below. (I made the label, feel free to use it yourself for free!) I attach it with clear packing tape covering the whole label. I also use spray paint to permanently cover all the other ...uh..."Mishaps"!

[Poodle Head Mikey]

I just thought of a reason for them to do this.

Could it be that the control-intent is to do a lot of the sensible load with the plate and only the remainder as both sensible & latent load with the finned coil? With the idea of lower frosting / longer air for for longer periods / less time devoted to defrosting. To do that really well the plate would have to controlled a degree or two above the dew point - is there anything sensing RH% ?

PHM
---------

This chamber actually has two evaporators. One is a standard coil and the other is cold plate. I can say now with certainty that its all 404A. But honestly, Im still a bit confused on the piping configuration. I see 3 solenoids that are tying both systems together. The manufacturer, Leica, refuses to provide any information like a schematic, wiring diagram, theory of operation etc. Very frustrating to say the least. I did find a compressor on Ebay for only about $100 so I think its worth replacing the bad compressor and see what happens.

Thanks for your input.
Semper Gumby

[MilfordsMrFixIt]

Hey Poodle, you could be right there. Sometimes the humidity is as or more important as the temperature! Good example; one of my customers had a walk-in humidor. The equipment had been mickeyed 20 ways from Christmas, once I 'started over' it wasn't all that hard to get the humidity and temperatures right. There are 2 compressors in that setup. One drives a fincoil, the other a plate. You might be on to something!

[MilfordsMrFixIt]

Hey NAVYGUY, did you ever post the model number of the equipment, I have access to a lot of the lecia tech sheets.

[Anisha]

Some compressors are designed to use different refrigerants so they can use different types instead of using one.

[captaincompressor]

404A is superior at low temps vs 134A

[VTP99]

R404a is the refrigerant of choice. Unfortunately it's slated to go on the EPA chopping block.

[captaincompressor]

R404a is the refrigerant of choice. Unfortunately it's slated to go on the EPA chopping block.

That's a shame because it works well for everything.

[pecmsg]

R404a is the refrigerant of choice. Unfortunately it's slated to go on the EPA chopping block.

That's on HOLD!

[captaincompressor]

That's on HOLD!

Good to know

[zymometer]

Hey NAVYGUY, did you ever post the model number of the equipment, I have access to a lot of the lecia tech sheets.

Have you worked on Leica CM1950 cryostats, with two separate refrigeration systems? On this model, the second refrigeration system is for the object holder. Leica uses flexible tubing to the object holder (since it moves up and down, in use). I've got a client with four of these machines. The older two are leaking refrigerant (404a) in the object holder system. I'm pretty sure that it is the flexible liquid line, which is leaking, but Leica doesn't list part numbers for it in the service manual. Have you run into this?

[zymometer]

Working on a small laboratory chamber that has 2 compressors, two condensers and no information whatsoever on it. One of the compressors is locked up tighter than a tractors nuts. The data plate on the equipment says it uses 404A. there is a sticker on the compressor that says 404A. But the actual data plate on the compressor says 134A. WTH? I went online and the exact replacement compressor says it uses 134A. So, can a 134A compressor use 404A?
This drives me crazy.
Remember when life was so easy when it was either R12 for refrigeration and freezing, R22 for AC and R502 for low temp?

I just wanted to say that this is extremely common on cryostats, which is (I presume) what you were working on. The OEM label on the compressor or condensing unit will say one refrigerant (e.g. 134a), but the equipment manufacturer (Leica, or Thermo, etc.) will specify and install a different refrigerant (and slap a label on it). Go with whatever the cryostat manufacturer specifies, not the compressor manufacturer (unless you have reason to believe that someone else has modified it in the field to a different refrigerant).

[zymometer]

I just thought of a reason for them to do this.

Could it be that the control-intent is to do a lot of the sensible load with the plate and only the remainder as both sensible & latent load with the finned coil? With the idea of lower frosting / longer air for for longer periods / less time devoted to defrosting. To do that really well the plate would have to controlled a degree or two above the dew point - is there anything sensing RH% ?

PHM
---------

Hi Poodle Head Mikey,
No, they are controlling the temperature of the cryostat chamber with the main (finned) evaporator. The other is a quick freeze plate, intended to quickly drop the temperature of small aluminum chucks (which are placed on top of the quick freeze plate during that time). The quick freeze plate will usually try to cool below the chamber temperature by another 20 degrees C or more. And usually the software will not allow the quick freeze circuit to start cooling, unless the chamber is already down to at least -5 or -10 degrees C.
Also, there is never an RH sensor in these instruments. Usually the main finned evaporator will be substantially colder than the quick freeze plate (except maybe for short periods of time). There is usually a daily or weekly defrost cycle - usually hot gas, but sometimes using an electrical resistance heater - but only for the finned evaporator and drip plate. After the defrost cycle ends, the main finned evaporator will capture the moisture left in the chamber.

[zymometer]

Hey NAVYGUY, did you ever post the model number of the equipment, I have access to a lot of the lecia tech sheets.

Hi MilfordsMrFixIt,
Do you have information on Leica CM1950 cryostats? It also has two separate refrigeration systems, but on this model, the second refrigeration system is for the object holder (not the quick freeze plate). Leica uses flexible tubing/hoses to the object holder. I've got a client with four of these machines. The older two are leaking refrigerant (404a) in the object holder system. I'm pretty sure that it is the flexible liquid line, which is leaking, but Leica doesn't list part numbers for it in the service manual. Do you have anything that shows the part numbers for these hoses or assemblies?
Those hoses/tubing have to be flexible at cold temperatures - this client runs the chamber at -25C, and the the object holder (the refrigerant through the hoses) can go as low as -52C; and the object holder moves up and down, during use, a couple of inches.

[Carrier12.]

404a without a doubt has superior performance characteristics and capacity compared to 134a. Love low the lower pressures of R134a but the temperature performance difference is no contest.