Hot head, low charge? Ship refridge system out of tune

[StrongPenguin]

Hi all, first post here. I've posted a bunch of data on the pictures, in hope to make the problem at bit more clear.

I am an engineer on a ship with a dual system (as is used on many ships here), with walk-in cooler and freezer running on the same compressor. The system seems to run fine, the cycles are short'ish and the daily run time is down from 15 hours, to 10. But the head is still very hot, and I am afraid of burning the compressor.

Pressure/data:

• HP : 10,8 bar
• LP : 0,5 (would like this to be 1,5 bar..I guess)
• Walk in freezer setpoint : -7 F
• Walk in cooler : 40 F (should be set lower)

The system runs about 10 hours a day, which is a great improvement from 15 hours, but it is still very hot. It was 250F on the head before I started messing with it, and now It's 230F, so a small improvement, but not much.

I have a suspicion that it's under charged, but the sight glass is totally clear (not empty) and the glass on the bottom of the receiver is also full.

Any suggestions for the hot head? I simply don't understand it, because on a sister ship, the LP is 0,25 and the head is 160 and no visible liquid in the bottom of the receiver. They are using R404A.

We recently had out evap replaced by professionals due to a serious leak, and had to change over to R407F. Now it runs hot, with even more charge than before. Could it be full of air? I have tried to purge it on the head, when it is stopped, only gas seems to escape.

[StrongPenguin]

I just opened into the cooler evap, and the TXV valve was totally frozen, just a big lump of ice. I defrosted the ice with a hot gun and noticed while defrosting, the pipes were ice cold and kept freezing, as soon as I removed the gun. The door was open, so the compressor is not supposed to start, but it seemed as if liquid kept flowing through the shut off valve and into the TXV. I also heard a hiss from the valve.

I did the same thing in the freezing room, and during the defrost with my gun, the pipes remained luke warm and did not freeze anywhere.

Smells like a leaky shut off valve.

[TechmanTerry]

What is the evap SuperHeat on both evaps? What is SH 6" before the comp? What is the Discharge Line temp 6" away from the comp? And is the SightGlassMoistureIndicator(SGMI) full while the comp is running? Is this a Pumpdown setup?

[StrongPenguin]

What is the evap SuperHeat on both evaps? What is SH 6" before the comp? What is the Discharge Line temp 6" away from the comp? And is the SightGlassMoistureIndicator(SGMI) full while the comp is running? Is this a Pumpdown setup?

The only measuring point for pressure is on the freezer evac, right before the TXV bulb. The pressure reads 0,9 bars there, which equals -43 F gas temperature. I had to use a thermometer to measure the various temperatures. I hope it can be used to tell something.

The discharge pipe 6" away from the compressor is -0,4 F

Freezer

-Pipe right after TXV: -29,2 F
-Pipe right before TXV bulb: -13,7 F
-Pipe 6" away: -16,3 F

Chiller (already frozen TXV again)

-Pipe right after TXV: 9,5 F
-Pipe right before TXV bulb: 18,5 F
-Pipe 6" away: 4,3 F

The sight glass is totally full, not a bubble in sight, and so is the bottom of the receiver. If you are referring to the hoses, that is because we fixed a leak on the upper compressor on the receiver and pumped it down afterwards. Then transferred a bit of R407F from the top receiver to the suction side of the compressor. It seemed to work fine, but you can't move a lot at a time, because the pressure drops drastically in the top receiver.

I also noticed that the suction pressure is 0,9 at the compressor, if the chill room evac is not running. When both are running, the LP side is 0,4 bar.

[pecmsg]

I'll guess the SH 6" from the pump is well above 40°F. If correct lowering that number will lower the discharge temperature.

Discharge temp is measures 6" after the discharge valve. 175°F is fine 175 - 200°F caution but still acceptable. 250°F and the oil is being baked!

[StrongPenguin]

I'll guess the SH 6" from the pump is well above 40°F. If correct lowering that number will lower the discharge temperature.

Discharge temp is measures 6" after the discharge valve. 175°F is fine 175 - 200°F caution but still acceptable. 250°F and the oil is being baked!

I don't understand what you mean by 6" from the pump. Is it 6" from the compressor suction intake? Still trying to learn HVAC talk.

The compressor discharge discharge line is about 160F measured on the copper pipe, before the condenser. But the head is 230F.

There is also a small amount of frost on the pipe just before the suction valve on the compressor, on the large pipe nut.

[pecmsg]

I don't understand what you mean by 6" from the pump. Is it 6" from the compressor suction intake? Still trying to learn HVAC talk.

The compressor discharge discharge line is about 160F measured on the copper pipe, before the condenser. But the head is 230F.

There is also a small amount of frost on the pipe just before the suction valve on the compressor, on the large pipe nut.

Suction line 6" before it enters the compressor.

Discharge line 6" after it leaves the compressor.

[StrongPenguin]

I also did an experiment by switching off the cooler evac. This resulted in an increase in the suction pipe close to the compressor, from 14F up to 40F. So no icing on the pipe, but head was still 230F. LP was 0,4 bar and HP 10,5 bar.

[Poodle Head Mikey]

What is the suction superheat at both evaporator outlets?

What is the suction superheat at the compressor?

What is the discharge superheat at the compressor?

PHM
--------

I just opened into the cooler evap, and the TXV valve was totally frozen, just a big lump of ice. I defrosted the ice with a hot gun and noticed while defrosting, the pipes were ice cold and kept freezing, as soon as I removed the gun. The door was open, so the compressor is not supposed to start, but it seemed as if liquid kept flowing through the shut off valve and into the TXV. I also heard a hiss from the valve.

I did the same thing in the freezing room, and during the defrost with my gun, the pipes remained luke warm and did not freeze anywhere.

Smells like a leaky shut off valve.

[StrongPenguin]

Suction line 6" before it enters the compressor.

Discharge line 6" after it leaves the compressor.

Suction line 6" before compressor: -1 F

Discharge line 6" after it leaves compressor: 167 F

This is measured on the outside of the copper pipe, since there are very few measuring points on this system.

[VTP99]

-1° f at the compressor suction 😲

[StrongPenguin]

What is the suction superheat at both evaporator outlets?

What is the suction superheat at the compressor?

What is the discharge superheat at the compressor?

PHM
--------

Sorry for being such an amateur, but how do I find these values? Could you give a brief description? The only place I can mount an actual manometer is right after the freezer evap. There are no measuring points in the cooler room. That's why I keep supplying these pipe measures

I was at home when the new freezer evap was installed, I have no idea which TXV is installed, or setting, or anything for that matter.

[pecmsg]

Suction line 6" before compressor: -1 F

Discharge line 6" after it leaves compressor: 167 F

This is measured on the outside of the copper pipe, since there are very few measuring points on this system.

What’s the suction pressure?
Box temperature?
167* is fine.

[StrongPenguin]

What’s the suction pressure?
Box temperature?
167* is fine.

Suction pressure: 0,4 to 0,8 bar. It depends on if both evacs are open. It is 0,4 bar if only the freezer is running, it seems.

What is box temperature? I can't find the lingo for box.

[pecmsg]

Suction pressure: 0,4 to 0,8 bar. It depends on if both evacs are open. It is 0,4 bar if only the freezer is running, it seems.

What is box temperature? I can't find the lingo for box.

The operating temperature?
With -1f the box should be -15 or -20*!

[StrongPenguin]

Oh, the box. The freezer is -6f and chiller is 48f.

Could it be the Txv is not adjusted? The guys only installed the freezer evac and left. No tuning as we did not have any R407F onboard.

[pecmsg]

Oh, the box. The freezer is -6f and chiller is 48f.

Could it be the Txv is not adjusted? The guys only installed the freezer evac and left. No tuning as we did not have any R407F onboard.

I’m confused
-6* box yet -1* 6” from the compressor?

Please
Temperature and pressure 6” from the pump.

[StrongPenguin]

I’m confused
-6* box yet -1* 6” from the compressor?

Please
Temperature and pressure 6” from the pump.

Like I said, this system is not fun to work on. I cant measure pressure 6" from the comp, because there are not any points. All I can provide is measurements of the pipe, which is -1f.

I will check if there are more measure valves tomorrow, but I doubt it.

IIRC the pipe right after the freezer evac measured -7f.

[VTP99]

O.6 bar = 8.7 psig
Approximately -33°f for R404a

[VTP99]

Suction pressure: 0,4 to 0,8 bar. It depends on if both evacs are open. It is 0,4 bar if only the freezer is running, it seems.

What is box temperature?

.