VMC44 Refrigeration low side pressure

[canton335]

I'm currently in the process of restoring my first ever machine (VMC44) and have a question on the proper refrigerant charge.  The unit is R12 and is running at about 18-19 PSI on the low side.  I think it's close to where I want to be based on information I've read on this forum, but I'm still seeing sweat back on the suction line almost to the compressor.  I'm currently running it with a new door seal, but minus the bottle rack at this point, so it's pretty much just an empty box.  Air temp in the box is cycling between 40F and 28F, and when I was doing this it was about 85F and very humid.

I feel like I may still be slightly over charged, but not being familiar with what's normal for one of these machines I didn't want to remove anymore refrigerant at this point without asking someone with more experience.

Any help appreciated,
Jeff.

[johnieG]

You should always weigh in the system charge per the tag on the compressor deck, never rely on just a pressure reading, how did you recharge the system?


Some  sweat on the suction line just past / outside of the bottle compartment may be normal , however icing of the line is not, I’ve noticed that anything over 20 psi tends to go with a flooded evaporator coil & as the system evaporator discharge air temperature gets down into the 30s you’ll see what you’ve described, the line may be only moderately cool, but a high humidity environment can lead to a dripping line. Also any restrictions in the evaporators air flow can ice up both the coils & the suction/return line

[canton335]

 Actually that's where I started.  Brazed a port on the process stub, pressure tested with N2, vacuumed and weighed in what the tag on the compressor deck said 1#. Which  gave me around 80 psi on the suction side. So I figured that wasn't correct, and adjusted the pressure down to around 18-19 psi which is where I'm at now.  I did notice a little bit of frosting that would melt and re-frost on the line close to where it exits the cabinet, but the line itself only felt cool further down. 

I was planning on waiting until I got the bottle rack and some cans in it before I made any more adjustments.  Not sure if this will matter or not, but right now it's only cooling the air in the cabinet.

Thanks for the information and help.  Much appreciated.

[johnieG]

Actually that's where I started.  Brazed a port on the process stub, pressure tested with N2, vacuumed and weighed in what the tag on the compressor deck said 1#. Which  gave me around 80 psi on the suction side. So I figured that wasn't correct, and adjusted the pressure down to around 18-19 psi which is where I'm at now.  I did notice a little bit of frosting that would melt and re-frost on the line close to where it exits the cabinet, but the line itself only felt cool further down. 

I was planning on waiting until I got the bottle rack and some cans in it before I made any more adjustments.  Not sure if this will matter or not, but right now it's only cooling the air in the cabinet.

Thanks for the information and help.  Much appreciated.

90 psi so as measured just after recharging the system before you turned it back on or with the system running? details details , also I assume (ha) that you charged it back up with R12? ( Just because you've said it was an R12 system doesn't necessarily mean you put R12 back into it), & out of curiosity, why did you have to recharge the system in the first place? 

me personally I shoot for 15 psi / R12 on the low side with the box at 32-degrees-F

[canton335]

So when I got the machine the compressor ran fine, but no cooling.   The compressor barely got warm, the condenser stayed room temp and so did the evap.  Turned out the steel part of the process stub below the brazed joint was pitted and the source of the leak. 

80 psi or 90 was with the compressor running for several minutes.

You are correct - 16oz. of R12 is what went back in.

15 psi is sounding pretty close to where this is going to end up if I'm trying to keep the suction line from sweating. 

Since the weight on the tag doesn't seem to be correct, and I've never worked on one of these before, I was wondering what the indicators of a properly charged system were. 

The info I got off this site so far has been great.  I feel I have it close, I was just a little concerned about the line sweating and didn't want to drop the psi down too far.

Thanks for the all the help. 

Anything else I should look at ?

Jeff.