Is there an easy way to refill holdover plates with Eutectic solution

[phorvati]

I have 2 large holdover plates. Each one has dual refrigeration loop. one used for engine drive and one used for 1/2HP 110V compressor at the dock.
I can see my freezer plate frost line stop right where i think solution level is. About 3 inches from the top plate never freezes. Freezer plate came from a technicold system. Original technicold fridge plate was replaced by seafrost holdover plate before my time.

Is there an easy way to add glycol solution or maybe drain and refill with known solution without removing plates or having to evacuate?

[OzeLouie]

The eutectic plates should have a filler with bung at the top.
Only top up to 90% full with phase change liquid and leave bung loose during initial re-freeze, tighten once liquid has frozen solid.

If no filler you could fit and *soft solder in a 3/8" / 1/2" brass union at the top then use a 3/8" bunk to seal off. (#81 flux*)

[phorvati]

I don't have a fill hole. Fridge is in use now. Is this an issue? I'm seeing a huge gradient inside freezer box. For instance at one point during cool down, txv bulb was at 14F, top of holdover plate was at 30F and bottom of freezer was at 24F. Freezer only has one plate on its side but nearly covers entire vertical dimension of the freezer box.

[Richard Kollmann]

Originally Posted by phorvati

I don't have a fill hole. Fridge is in use now. Is this an issue? I'm seeing a huge gradient inside freezer box. For instance at one point during cool down, txv bulb was at 14F, top of holdover plate was at 30F and bottom of freezer was at 24F. Freezer only has one plate on its side but nearly covers entire vertical dimension of the freezer box.

Your posts are confusing to me in that Technautics and Seafrost both have fill plugs unless the Seafrost plate does not contain liquid eutectic solution. Is the Seafrost plate cast aluminum or welded stainless? Could it be that plate is rotated so fill plug is on a side or bottom? Seafrost aluminum plates do use a gasket sealing plate. all other stainless plates now seam weld covers on plates after securing evaporator to plate skin.

Another confusing point is plate's frost cover and txv bulb temperature as high as +14 F. If freezer plate say has a zero or even a 10 degree eutectic solution to freeze it, bulb temperature should be well below +14 F. Just before thermostat stops compressor what condition do you see in sight glass? And the next time compressor is running for 30 minutes what condition do you see in sight glass?

Nothing so far would tell us the problem is loss of eutectic solution it actually sounds like compressor stops before solution is completely frozen up to the top. Or system is low on refrigerant or condenser cooling is inadequate.

[Coolerking]

The fill port is between the refrigerant lines on the plate if its a technautics.
We do lots of seam welding for them.
To be honest Richard is correct, this sounds like a refrigerant charge issue, or a control that is cycling early.

[phorvati]

Seafrost (cast aluminum)did have a screw on top which I was able to crack(its moving, i didnt strip it). So now the question is what to put in for solution. Did seafrost use something specific and how to i find out.

Richard, to answer your questions and maybe post another, yes I have something else mysterious going on. My system is R134A. 14F was not after plate reached set point. I am still to measure/adjust super heat. My main issue is floodback. See pdf for schematic capture of my system (DIY)

When my thermostat shuts the compressor, I get liquid floodback. I know because on subsequent starts I get locked rotor. This is reproducible and its been haunting me for some time now. It happens even after adding suction line accumulator. At the moment I am not using the fridge plate(only freezer) in hopes of determining the root cause of floodback.

Another observation to add is As my set point is reached and compressor shuts off, my gauges over time go to 30PSI suction and 50PSI discharge. They seem to settle there. At that suction pressure on startup, I noticed the floodback and locked rotor(40A AC mains draw). If i let refrigerant out of the suction side down to where gauge is showing < 20PSI. now compressor can start. Ive had this happen last fall. And its reproducible. Ive downsized the AC mains breaker to 10A, and now locked rotor trips it almost immediately (Saving my compressor). It happened yesterday. In the meantime I changed freezer TXV (Danfoss T2) with Sporlan FJ-1/4C because it was leaking at the adjustment screw cover.

Floodback did not occur through 1 cycle with 1 can of refrigerant in. But 24 hours of runtime did not get the freezer temperature past 26F. After I added another 3/4 Can I got to 19F in the freezer box easily but I also got the floodback.

My next step is to accurately measure superheat. The issue is my freezer suction line goes through fridge box un-insulated and then I insulated it once its out of the fridge box where it joins the fridge suction line. My freezer suction line is un-intentionally cooling the fridge box. So I believe This temperature drop on that line from the TXV bulb to compressor service valve is too big to accurately measure super heat. for 5 feet of 3/8" suction line what is pressure drop? And if temperature of that line changes from 14F at the TXV bulb to 55F at the compressor where i measure 0psi, how do i compensate to accurately measure superheat? or do I need pressure reading at TXV bulb. I don't mind cracking the refrigeration open again to add a pressure gauge.



I think I also want to add the solenoid to freezer line. or ranco LP switch in order to handle floodback. I just want to find the root cause first. Could it be that my refrigeration lines in the cold plate are too big for 1/2HP compressor. I have dual coils in my holdover palte. Second loop was meant for engine drive. Perhaps I have used the engine drive loop to hook up the 1/2HP 120V AC compressor so that line is now too big accumulating too much refrigerant and contributing to floodback?

[OzeLouie]

Your system diagram pdf attached is incorrect, hopefully just a drawing error.
Each condenser must have refrigerant enter at the top and cascade downwards to exit at the bottom. (Not as shown in your diagram)
What size orifice do you have in the TX valve and is the valves sensor bulb insulated? Are you sure that the suction accumulator is correctly coupled?

If you add a solenoid to the freezer liquid line, you could also add a low side pressure switch and operate as a pump down system eliminating any possibility of liquid accumulating in the compressor. The thermostat would then function the solenoid and the low (and high) pressure switches would switch the compressor. Set low PS to off at say 2PSIG and on at 25PSIG. A pump down system is best for oil retention in compressor, a concern if liquid is accumulating in there.

[Richard Kollmann]

Unread Today, 13:58 #6
phorvati
Adding solution and Super heat adjustment is the last thing to worry about as there are simple fixes there. Line sizes inside and outside also do not appear to be a problem on AC 110 volt system.

Refrigerant volume flow and refrigerant volume seem to be your problem.
It would really help to see sight glass flow at varies times during compressor run cycle.

The compressor overload on start could be one of the following:
1. Is locked rotor caused by External circuit breaker or compressor internal overload switch.? Are you aware of the locked rotor rated amperage? Normally ½ HP 110 volt compressor LRO is 40 to 50 amps and running amps 9 to 12 amps.
2. If there is a King valve on side of receiver is it wide open?
3. The problem could also be the suction line accumulator is connected backwards Check direction arrows on accumulator.
4. The orifice inside TXV than a one O and preferable OO.
5. Also report back the location and attachment method to suction line
6. Also report temperature of TXV 30 minutes after compressor start up. A balanced system at that time will cause your finger to lightly stick to TXV.

[Coolerking]

A FJ-C is for refer plates.
You need a FJ-Z for the freezer plate.

[phorvati]

My condenser polarity is correct. Heat exchanger has labels which i followed when installing it last year. And the same is the case for the air condenser. i just made a mistake in schematic.

sight glass
I have bubbles but large voids of no liquid(i feel) but liquid is clearly flowing. It never completely turns into pure liquid with no bubbles.


I am assuming its locked rotor. compressors trying to start but not starting. As compressor tries to start, I see 40A on the AC mains panel. Now that i have a 10A circuit breaker, that trips within 1 second. with old 20A circuit breaker, I would shut it off about 1-2 seconds after I see the 40A on the dial. I never let it run drawing 40A to find out if old 20A breaker would trip. I was very cognizant of this and I made it a point to observe every startup. (PITA but wanted to make sure i don't ruin the compressor)


King valve on side of receiver
Cracked so I can monitor high side. 50psi on startup, but rises up to 75psi. Air temperature is still chilly in RI. 50s, and ocean water is 45F. Refrigerant line exiting compressor is very hot. And by the time it leaves both condensers its basically 45F. Maybe i'm running too cold?


suction line accumulator is connected backwards ?
Checked for the 10th time and it is correct. There is an IN label and that's where line from evaporator comes into.

4. The orifice inside TXV than a one O and preferable OO.

I have to check this.

5. Also report back the location and attachment method to suction line

see pics, and let me know if you need more.

6. Also report temperature of TXV 30 minutes after compressor start up. see pics.
Using IR thermometer that I calibrated against my skin, I had 0F all along the bottom of the freezer plate and at exit of TXV. prior to frost I might have had lower temperatures -10F i think but i will check at next cycle.
22F at top of freezer plate and at the exit of the bulb. I don't want to take off the bulb insulation. Could frost be insulating my real temperature?

Ice cream is solid, so i am in dream land right now. Its just a matter of finding the root cause of floodback.

[phorvati]

Originally Posted by OzeLouie

If you add a solenoid to the freezer liquid line, you could also add a low side pressure switch and operate as a pump down system eliminating any possibility of liquid accumulating in the compressor. The thermostat would then function the solenoid and the low (and high) pressure switches would switch the compressor. Set low PS to off at say 2PSIG and on at 25PSIG. A pump down system is best for oil retention in compressor, a concern if liquid is accumulating in there.

Attachment 237851

One other thing.

With freezer only running, so fridge solenoid OFF because t-stat is not calling for cooling, Compressor operates in vacuum. About 5 inches. It gets to vacuum fairly early within 10 minutes of startup. Once fridge loop opens, suction goes up to 5-10-PSI. So how would i set the LP switch?

We opened the freezer TXV about 3 quarter turns CCW. at the first startup a week ago. I have not touched it since. I did that because at the time I thought it needed a "kick" and the hope was to get out of vacuum when freezer only loop is flowing. But in retrospect, im not sure It did anything for me. Sight glass is green, but i have 3 spare dryer/filters. Should i replace it? Its really easy with the packless valves there.

[OzeLouie]

Originally Posted by phorvati

One other thing.

With freezer only running, so fridge solenoid OFF because t-stat is not calling for cooling, Compressor operates in vacuum. About 5 inches. It gets to vacuum fairly early within 10 minutes of startup. Once fridge loop opens, suction goes up to 5-10-PSI. So how would i set the LP switch?

We opened the freezer TXV about 3 quarter turns CCW. at the first startup a week ago. I have not touched it since. I did that because at the time I thought it needed a "kick" and the hope was to get out of vacuum when freezer only loop is flowing. But in retrospect, im not sure It did anything for me. Sight glass is green, but i have 3 spare dryer/filters. Should i replace it? Its really easy with the packless valves there.

Great information.
Now to find where the liquid is coming from to cause the comp lock up.

With gauges connected, close off hand valve 2 and run the system down on a deep vacuum. Switch off and monitor gauge pressure changes. You may need to do this consecutively several times but ideally the suction pressure should only rise very slowly, a little when switched off then not at all with B shut and if the comps discharge valve is ok, then we can determine if the flood is via the low or high side.

[Coolerking]

Again, you said that you changed out the txv on the freezer to a "C" charge.
You need a "Z" in there to have it run in a freezer range.
It won't get to temp with the wrong txv as it will close down far too early.

[Richard Kollmann]

There is to be only one restriction in the refrigerant loop and that is the TXV flow control. You report compressor overload and very low suction pressure. You also report sight glass bubbles. The TXV when purchased was set to mid range that would not cause the flow restriction and compressor overload you are describing. The lack of full sight glass would indicate if it is installed before TXV the over load restriction condition is between compressor and sight glass. If sight glass is installed after TXV then it may be a clogged screen in valves orifice restricting flow.
Based on what we know now I have to ask again is king valve wide open? Having gauge on king valve is OK but valve needs to be in the full open as far as it will go position. Your low reading at king valve of less than 100 psi and a vacuum of 5 inches problem is between king valve and compressor. If restriction is not the King valve it will be a solder joint in high pressure side of system because if restriction is in low pressure side of system there would be a cold spot there or even frost.

[phorvati]

Originally Posted by Coolerking

Again, you said that you changed out the txv on the freezer to a "C" charge.
You need a "Z" in there to have it run in a freezer range.
It won't get to temp with the wrong txv as it will close down far too early.

It appears that z is not available for r134a in the type I have FJ-1/4