Refrigeration Problem

[lions paw]

I have been fighting refrigeration problems for the last 4 years but this problem has me stumped. I have a separate freezer unit with two large holding plates run by a Danfoss compressor with a capillary tube. The plates run in series first to the plate with the capillary tube then out of the box to the plate on the other side of the box then back to the compressor (Normal). The unit was working properly with both plates frosting and the temp of the box freezing things properly. Then the first plate (the one with the capillary tube refused to frost up and went to box temp.. I assumed that I had too much Freon and over a couple of day reduce the charge until I was down to 2 psi and the second plate would not freeze. I was in the middle of nowhere so I increase the Freon to about 14 psi froze the second plate and a length of the return tube and reduced the box size This got me through the season. Now I am In the Rio Dulce try to figure it out. I checked and the plate is full of “antifreeze”. Does anyone have any subjection as to where I should go from here?
Some history the last thing done to this unit was the installation of a dryer, vacuumed and Freon. This was two weeks before the problem.
Steve

[SV THIRD DAY]

Hola Lions Paw...
It could be helpful for us to know the system type, is it a home brew system or one from a manufacturer?

With two holding plates plumbed in series, the system "sees" the two plates as one big evaporator along with the copper tubing connecting the two plates. So it's odd to see them behaving differently. It the compressor is running, most of the time it boils down to a charge issue and from the data that your return tube is now frosty...it sounds like you are now over-charged. Does the manufacturer give any charge data at to the amount of refrigerant designed for the system?

[Cavalier]

Originally Posted by lions paw

Then the first plate (the one with the capillary tube refused to frost up and went to box temp.. I assumed that I had too much Freon and over a couple of day reduce the charge until I was down to 2 psi and the second plate would not freeze.

Some plates are designed with an inbuilt passive bypass. i.e. there'll be a very small diameter cavity that runs from the inlet to the outlet. Most of the time the majority of the coolant will evaporate throughout the main bore of the system. In the event that the main bore becomes blocked, or restricted etc. (due to internal corrosion or foreign particles), then the Freon will bypass most of the plate and transfer to the outlet at a much lower rate.

This may explain why your second plate still works (down to a low pressure) but the first plate in series has stopped functioning. If this is the case then you're unlikely to notice any change in the performance of the compressor, as the blockage would only have affected the

If you have a vacuum and Freon charging system available (sounds like it). You could consider removing the blocked plate from the system to see how well the second (functioning) plate works. Alternatively, you could remove the functioning plate and confirm that the first plate is blocked.

[SV THIRD DAY]

Originally Posted by Cavalier

Some plates are designed with an inbuilt passive bypass. i.e. there'll be a very small diameter cavity that runs from the inlet to the outlet. Most of the time the majority of the coolant will evaporate throughout the main bore of the system. In the event that the main bore becomes blocked, or restricted etc. (due to internal corrosion or foreign particles), then the Freon will bypass most of the plate and transfer to the outlet at a much lower rate. .

Cavalier's good point highlights the need to know what type of system you have so we can give the right advice.