True Reach in Cooler

[The_chief]

I have a question about a unit I was working on.

I responded to a call about a unit that was making a smooshing noise every 5 min or so while the unit was running. I get there and first thought was internal relief valve. I throw some guages on...

Low side 45 psi (10 degrees)
High side 330 psi (125 degrees).
Cap tube with subcooling of 50 degrees?? Liquid line was 75 degrees.

Every time the swooshing noise starts the High side opens the relief at 330 psi it and closes at about 250ish.

The part I dont understand. There is a suction dryer installed. The first time I took temp split across the drier I had 14 degrees differance. I assumed this would cause a restriction and make refrigerant back up in the condensor. A few minutes later I checked again and it was only a 1.5 degree diff across the suction dryer.

This is where I am stuck. Any thoughts?

[invisiblecollar]

What kind of refrigerant?

[craig1]

There was probably liquid refrigerant sitting in the evap, which got sucked out and collected in the suction line dryer when the comp started. As this liquid evaporated it created the temp drop you saw.

[The_chief]

What kind of refrigerant?

Unit is 404a

[The_chief]

There was probably liquid refrigerant sitting in the evap, which got sucked out and collected in the suction line dryer when the comp started. As this liquid evaporated it created the temp drop you saw.

If that is true then I am really at a loss of what this could be..

[craig1]

is the condenser clean?

[The_chief]

is the condenser clean?

Yes the condensor is clean.

[DDDpope]

Without hands on this is only a guess but should be checked. POE oil breaks down under high condensing temperatures to a very fine powder that will go through driers, screens and cap tubes, causing partial restrictions. It will also coat the inside of the condenser and evaporator. If you find this fine black/gray powder in the system, that is the problem. The fix is to flush the system and replace the cap tube or tubes. Also don't forget to replace any driers and the cap tube strainer. Last of all, be aware that the problem could have caused damage to the compressor. This could become an expensive fix. I hate/love POE oil.

[VTP99]

Is that a suction dryer or a suction accumulator ?

[cmclifton]

Sure it's a cooler and not a freezer? I haven't seen a True cooler that had 404a in it, usually they're charged with 134a.

More often than not a restriction in the system doesn't cause high head pressure unless it's before the condenser, in the compressor discharge line. Look for the obvious, of course. Kinked copper or whatever. Some of those things have steel discharge lines, someone may have got a little bit crazy with the 56% silver brazing in a new compressor and partially filled the discharge line.

Condenser fan spinning the right way? IIRC those things use the little shaded pole motors you can pick up at any supply house, someone may have put the wrong one in.

[The_chief]

Is that a suction dryer or a suction accumulator ?

Suction Dryer

[The_chief]

Sure it's a cooler and not a freezer? I haven't seen a True cooler that had 404a in it, usually they're charged with 134a.

More often than not a restriction in the system doesn't cause high head pressure unless it's before the condenser, in the compressor discharge line. Look for the obvious, of course. Kinked copper or whatever. Some of those things have steel discharge lines, someone may have got a little bit crazy with the 56% silver brazing in a new compressor and partially filled the discharge line.

Condenser fan spinning the right way? IIRC those things use the little shaded pole motors you can pick up at any supply house, someone may have put the wrong one in.


I mispoke and it is a McCall Freezer/Refrigerator according to name plate.

As far as kinks and bends I did not see any. No frosting on liquid line.

Fan is going the right way.

[icemeister]

I mispoke and it is a McCall Freezer/Refrigerator according to name plate.

As far as kinks and bends I did not see any. No frosting on liquid line.

Fan is going the right way.

A refrigerator/freezer is a horse of a different color. ;)

If it's a single compressor model, that whooshing you describe may be from a liquid solenoid valve to the refrigerator section cycling on and off. If that's the case you appear to be overcharged when running only on the freezer section.

If you do have a restricted cap tube, the system may have been overcharged to get the suction pressure up...resulting in the high head pressure and high subcooling.

If you do replace the cap tube, it's imperative that you also change the compressor oil. If you don't, you'll be back fairly soon because the crap that plugged it up is still lurking in that dirty oil.

[The_chief]

A refrigerator/freezer is a horse of a different color. ;)

If it's a single compressor model, that whooshing you describe may be from a liquid solenoid valve to the refrigerator section cycling on and off. If that's the case you appear to be overcharged when running only on the freezer section.

If you do have a restricted cap tube, the system may have been overcharged to get the suction pressure up...resulting in the high head pressure and high subcooling.

If you do replace the cap tube, it's imperative that you also change the compressor oil. If you don't, you'll be back fairly soon because the crap that plugged it up is still lurking in that dirty oil.


I wasnt very clear on the the refrigerator/freezer. It is a refrigerator OR freezer.


If there was a restriction in liquid line wouldnt there be frosting?

[VTP99]

I wasnt very clear on the the refrigerator/freezer. It is a refrigerator OR freezer.


If there was a restriction in liquid line wouldnt there be frosting?

Chief,
Is it a refrigerator on one side and a freezer the other or top & bottom ?
Or is it one box bilt for one or the other app. ?
Just to be clear.

[pdrake65]

How about a model # so we can see what you are looking at? Very confusing!

[The_chief]

Sorry guys I will get some info.

[VTP99]

I mispoke and it is a McCall Freezer/Refrigerator according to name plate.

As far as kinks and bends I did not see any. No frosting on liquid line.

Fan is going the right way.

Was at a Arby's today working on a Bunn coffee machine when i noticed that they had a McCall. Opened the top door of a top & bottom door unit and what did i read on the tag (Refrigerator or Freezer) . This one was a freezer top & bottom. On a side note the Bunn had a bad inline thermal fuse for the heater. ;)

[cmclifton]

If there was a restriction in liquid line wouldnt there be frosting?

A partial restriction in the liquid line would usually cause frost or condensation, yes. It would also usually cause the pressures to drop, making it look like it's low on refrigerant. Then someone might be confused and add refrigerant to it, at which point it could eventually start bringing the pressures up once they've flooded the condenser with liquid to the point that there's just not enough room in the system to hold all the gas.