Marine Refrigeration Problem

[wifiguy]

I have about 10 years experience working with marine refrigeration but have come across a problem that I can't seem to solve.
I'm hoping someone can help me with this problem.
The system is a Technautics inc. Danfoss DB50. Small holding plate system with an expansion valve.

System was a little low on gas - Topped it up with R134a
System not pulling down passed 30 psi on low side but still bubbles in sight glass so vacuumed it for over an hour and refilled but still not pulling down on low side. High side not going up over 60 psi.
Fitted new compressor with some results.
Changed filter dryer - no change.
Took off expansion valve and checked for blockages both ways high and low side and checked valve - all OK.

Anyone have any ideas, Please.
THX,

[Blueboy]

Hi

There are only a couple of things this can be and I think you have covered them all , so maybe you need to do it again. From the top.

1) One Check you have condenser water ( marine right ) Are you using General Fresh water or direct sea water , if sea water check you strainer. If air cooled blow condenser with Nitrogen.

2) Replace the TEV ( it is the only thing you haven't done) be sure to get the right sized orifice.

3) Using a torr gauge ( micron gauge is equally good ) Pull a good vacuum remember vacuum is measured in Microns Hg or Torr not time - Time is of no consequence.

4) Make sure the vacuum holds - Good No leaks them .

5) Recharge carefully with the exact quantity of refrigerant required , small systems are often super critically charged.

6) Now Given you have the same compressor and it is pumping efficiently the system should work.

last thing when I have problems like this I sometimes fit a high side and low side schreader valve so that I can see the operating pressures this will also help if you are not sure how much gas to put it .

Good Luck

[Blueboy]

Hi

There are only a couple of things this can be and I think you have covered them all , so maybe you need to do it again. From the top.

1) One Check you have condenser water ( marine right ) Are you using General Fresh water or direct sea water , if sea water check you strainer. If air cooled blow condenser with Nitrogen.

2) Replace the TEV ( it is the only thing you haven't done) be sure to get the right sized orifice.

3) Using a torr gauge ( micron gauge is equally good ) Pull a good vacuum remember vacuum is measured in Microns Hg or Torr not time - Time is of no consequence.

4) Make sure the vacuum holds - Good No leaks them .

5) Recharge carefully with the exact quantity of refrigerant required , small systems are often super critically charged.

6) Now Given you have the same compressor and it is pumping efficiently the system should work.

last thing when I have problems like this I sometimes fit a high side and low side schreader valve so that I can see the operating pressures this will also help if you are not sure how much gas to put it .

Good Luck

[wifiguy]

Very much appreciated Blueboy, I will change the expansion valve today and see what happens.
Have a good weekend,
R.

Hi

There are only a couple of things this can be and I think you have covered them all , so maybe you need to do it again. From the top.

1) One Check you have condenser water ( marine right ) Are you using General Fresh water or direct sea water , if sea water check you strainer. If air cooled blow condenser with Nitrogen.

2) Replace the TEV ( it is the only thing you haven't done) be sure to get the right sized orifice.

3) Using a torr gauge ( micron gauge is equally good ) Pull a good vacuum remember vacuum is measured in Microns Hg or Torr not time - Time is of no consequence.

4) Make sure the vacuum holds - Good No leaks them .

5) Recharge carefully with the exact quantity of refrigerant required , small systems are often super critically charged.

6) Now Given you have the same compressor and it is pumping efficiently the system should work.

last thing when I have problems like this I sometimes fit a high side and low side schreader valve so that I can see the operating pressures this will also help if you are not sure how much gas to put it .

Good Luck

[Mayball]

Hi wifiguy,
I have had some experience with the Technautics Cool Blue system, and have recently installed two new condensing units replacing a 110 volt system with cold plates and thermostat/solenoid control. A couple of things I have found with these systems:

1. The system runs best with a few bubbles in the sight glass. I believe the reason for this is that the filter/dryer/receiver/sight glass is too small. When you charge the system with enough refrigerant to clear the sight glass, the receiver completely fills and liquid backs up into the condenser, causing the discharge pressure rise radically. Obviously, this is not your problem at this time if the TEV is sticking open.

2. The expansion valve (with the superheat supposedly set properly by Technautics) is often set with the superheat too high. I often find it necessary to adjust it to achieve a 9 to 10 degree F superheat, and get the full use of the cold plate.