R-404 Breakdown

[r.graves]

I have a walk-in freezer that runs r-404 i have run across a problem with the breakdown of the refrigerant, the refrigerant does not cool head pressure increases and low side drops. No acid in system, filters changed out, i can remove refrigerant and recharge in works fine for a few days and then will not cool. The refrigerant has a bad smell to it but the compressor has no over amp. and nothing to ground. Any ideas????

[Gary]

A lot more information is needed, but my guess at this point (and its just a guess) would be plugged TXV inlet screen.

The refrigerant is NOT breaking down.

[r.graves]

txv i clean nothing i the screen, superheats normal

[Gary]

We need to know the air in/air out temps on both coils, the liquid and suction line temps, and the pressures.

[glenn1340]

Just wondering Gary ( and I bow to your far superior knowledge) could the refrigerant BE breaking down (not sure if r graves is recharging with virgin refrigerant) as I`ve come across units with r407c that have had small enough leaks to cause the refrigerant to fracture but not enough to notice on the scales when recovered. This could account for the "bad smell" of the refrigerant (possible very high delivery temp perhaps) and the fact that the equipment runs ok for a few days befor the problem re-occurs.
Anyway just my thoughts, probably way off track.

[Gary]

Theoretically, fractionation can occur with just the right leak in just the right place at just the right temperature, but I haven't seen it. Every time I think this is the case, the problem turns out to be something different altogether.

I'm beginning to think fractionation is at least exceedingly rare... if not an outright myth.

[glenn1340]

Hi Gary,
I`ve come across fractionisation on three occassions all on 407c in compressed air dryers. Really a pain to confirm. On two occasions the high and low pressures showed ok but the dew point of the compressed air would not drop below 10c. Third case the high side temp switch cut out the dryer. Carried out pressure tests with nitrogen and foung very small leaks under insulation at solder joints. Since the repairs there`s been no probs with the dryers.