R12 cold plate refrigeration

[farniente]

Hope someone can answer my question about my boat refer .
It's an R12 system with two cold plates in series.
One Danfoss tev at the inlet of the first plate (brine solution)and the sensing bulb at the outlet of the 2nd (antifreeze solution).
Sanyo 508 compressor with seawater condensor,sightglass receiver and filter dryer and finally a suction accumulator.
I recently noticed the suction accumulator and line to the compressor was frosting at start up.
At start up low pressure is 20lb and high pressure is 140lb. Within two minutes low pressure drops to 10"hg and high pressure is 145lb. Ambient about 70F.
I called a tech out, to the boat, he adjusted the super heat and said it wa fine. The compressor is still running in a vaccumn.
The system has run fine for 8 years, why would the super heat suddenly need adjustment and is it OK to run in a vaccumn?
Thanks, Terry

[old gas bottle]

should have changed the liquid line drier first at that age,then if still no good i would have changed the TEV also,should only touch a vacum when right down to temperature if that, watch the oil level in the compressor if possible as it will loose its oil around the system if not carefull, get the guy back.

[farniente]

Thanks for the info.
I'm not sure I want this guy back on my boat.
If I understand you correctly I need some one to recover the R12, flush rhe system,change the drier and comp oil and then recharge .

,

[old gas bottle]

it might all pump into the reciever for the repair or most of it at least, treat it to a new valve and drier, standard superheat as set in the factory,fitted just as it was but insulate the bulb that might help with the frosting back, and it should be o/k, i used to fit them 30 years ago in trucks, "oh" the memorys,[bloody heavey old things.} good luck.

[farniente]

Thanks again.
I'll post the results.
Terry

[Andy]

Thanks for the info.
I'm not sure I want this guy back on my boat.
If I understand you correctly I need some one to recover the R12, flush rhe system,change the drier and comp oil and then recharge .

,

Farniente:)

don't you mean evacuate the system with a vacumn pump;)

Kind Regards Andy:)

[farniente]

Hi Andy,
If I recover the entire system then I will evacuate it,otherwise I will take Old gas bottle's advise and pump it into the receiver.
I am a plumbing contractor ,so I have a basic grasp of the sitituation, however any further input would greatly appreciated.
Regards, Terry.

[Andy]

Hi Andy,
If I recover the entire system then I will evacuate it,otherwise I will take Old gas bottle's advise and pump it into the receiver.
I am a plumbing contractor ,so I have a basic grasp of the sitituation, however any further input would greatly appreciated.
Regards, Terry.

Hi farniente:)

in the past refrigeration systems were purged to blot out air and moisture, R12 R502 and R22 were common.
All these refrigerants are now banned in new installs, indeed R12 and R502 should be recovered and replaced by a drop in whilst servicing. It is likly that you system has an R12 drop in such as R401a or R409 not R12.
If that is the case the outlet valve on the receiver should be shut and the system pumped down to as near 0 psig as practicible. The components in question should be replaced (the section broken into should be pressure tested with oxygen free nitrogen to at least the hp switch setting or 1.1 times the releif valve setting if you are being proper) and a vacum pump should be used to about 1000 microns to esure air and moisture removal. The valves should then be opened up and the superheat subcool and refrigerant charge checked.

Kind Regards Andy:)

[farniente]

Hi Andy,
Is it still leagal to top off am existing R12 system with R 12?
I have a large jug of R12 from when the system was origanally
built.
When you refer to a drop in refrigerent does that mean it is compatible with the R 12 and oil that is in the systrm now?
Thanks again,
Terry

[750 Valve]

Pump down, inspect strainer in TXV - replace if clogged - shouldn't be but with whats happening on startup it sounds like its starving (either from txv strainer or drier) - replace drier - evacuate and run and test superheat

Is the whole txv body frosting/sweating (inlet, main body and power element)? If so then its more than likely a blocked strainer.

[farniente]

Hi,
The Tx valve body is very lightly frosted .
The power head is not.
Ther is also no frosting on the line after the filter drier, however the
accuulatour and line to the comppressor frost for about 2 minutes at start up.
Regards ,Terry.

[farniente]

Hi 750 valve,
The TX valve body is very lightly frosted but not the power head.
No frosting near the filter dryer.
Heavy frosting at the accumulator and line to comp for about two minutes at start up.
Regards Terry