Refrigeration system possibly overcharged...???

[Typhoon]

A sight glass positioned close to the the Thermostatic Expansion Valve (TXV/TEV) is the best way to be sure of a proper charge . Mounting it horizontally gives the best results .

Regards John.

https://www.youtube.com/watch?v=ACaS7Cavt-k

[Locquatious]

Seems like you have competent advice.
In the past we found that the start relay was not in the correct orientation. Sometimes they are gravity helped for proper contact engagement.

[Jammer]

I agree that the problem is unrelated to the sealed system. Have a look at the clutch and belt.

First of all, measure the belt tension. Get a Krikit belt tension tester (small and $15 or less) if you don't have one. Not sure what tension to use? There's a chart here:

http://www.daycoproducts.com/stuff/c...._4.18.13_.pdf

If the tension is wrong, fix it.

Next move is to measure the clutch voltage at the compressor being sure to get an accurate measurement, while the compressor is running. Connect your test lead on the clutch side of any connectors or terminals. Many if not most clutches are two-wire and so you want to measure between the two wires rather than the voltage to ground. You should observe at least 12 volts.

If the voltage is low, you have an electrical problem to trace, probably a bad connector or switch. Many systems have cutoff switches for low and high refrigerant pressure, and these can fail, as can the connections to them.

If the voltage is OK, you need to overhaul the clutch. Whether the problem is the bearing, the friction surfaces, or the magnetic coil is sort of beside the point since if you go to the trouble to take the thing apart you'll want to replace all those components. You may find problems getting service parts that will fit properly. I've had to replace entire compre$$ors due to unavailability of clutch parts. Good luck.

If you end up with parts availability problems you may be better off replacing the compressor and motor with a single sealed unit.

[Rorzech]

Your compressor could be slugging liquid, which doesn't compress. Could be over charged. Your expansion valve could be stuck partly open. Once it's running look to see how far the frost back is on the suction line. If it's a capillary system maybe the cap and suction line are separated the full length of the lines. Lots of things can contribute to the problem.

[stormalong]

I am curious. I had an electric drive holding plate system - replaced about ten years ago with dual BD50's.

Why is there a clutch at all. Mine just turned the motor on and off - no need for a clutch.

[MoonlightSailor]

Thanks Senormechanico for your 2 cents...makes complete sense. Can bearings be bought and replaced without having to replace the entire clutch?

I don't think the bearings are the source of the problem for the clutch slipping when engaged. Would I be right?

The system ran for 2-3 hours.
Low pressure got down to 3
High pressure stayed at 100

I can't explain the clutch operating the way it is...just weird...

Here is how the powering down went last night when gauges were attached to compressor:

I closed the in-line valve above the sight glass. (I was taught by the prior refer specialist that worked on the system that closing the valve is beneficial and will move the freon to one side of the system)

1. The low side pressure switch turned off the clutch at about -8.
2. Turned off compressor.
3. Closed valves on gauges
4. Disconnected the low side gauge hose at compressor
5. Back seated the high side rota lock
6. Disconnected the high side pressure gauge hose as quickly as possible. When I disconnected the high side I was blasted with about a tablespoon of oil along with refrigerant. I believe this was due to more pressure in the high side because I closed that valve to get the clutch to turn off via the low pressure switch. Thinking back...I would not have closed that valve but would have left it open, turned off system and then removed the gauges from compressor. That has always been my shut down procedure and I didn't think of the effect it would cause when I removed the high pressure hose.
7. The ice box got down to sub zero temperatures!

Only question I have is did I lose too much oil when I removed the high pressure gauge hose from the compressor? I'm thinking probably not.

So....just now I turned on genset and powered up the clutch to the compressor.

Compressor clutch engaged without any sqeaking. Didn't act like it was under too much of a load on start-up.
The head of the compressor started to frost up and I turned off the clutch and waited for it to defrost.
After it defrosted, engaged clutch and compressor. Frost didn't go below the rotalock onto the compressor head.
This has been typical of past operation and rarely does the frost go below the rotalock to the head. Frost on rotalock eventually disappears after a few minutes.

[Richard Kollmann]

The picture shows a York aluminum compressor and a twin pulley standard clutch. If you Google (York AC compressor clutch removal ) there is a good explanations of clutch bearing replacement there. If the clutch bearing were bad on this model clutch your movie picture would show a wobble and it does not.

Like I reported before your refrigerant pressures are almost normal for that configuration of your systems design. Bad information circulated in print thirty years ago convinced boaters to run these automobile compressors at too high a speed. What complicates your system more is the electrical motor driving compressor’s fast start up speed. In a refrigerator compressor start up there is a pump down phase where refrigerant is removed from the low pressure side of system and restricted only by the refrigerant flow control device expansion valve and maybe a suction line liquid accumulator. The previous owner must have had compressor freeze up failures before to develop the procedure of storing liquid refrigerant in high pressure side of system. On engine driven systems similar to yours I recommend engine is operated a few minutes at idle when clutch in engaged. I have to assume the overload start problem you experienced was refrigerant trapped in high pressure side of system you opened red refrigerant valve.

The frost build up on start you describe of suction line frosting on fitting at compressor is pretty much normal but not when frost forms of compressor head. High suction pressure in the beginning confirms expansion valve orifice is oversized. Once TXV valve temperature sense tube cut valve flow down to the right size system performs normal dropping low side pressure slowly to five psi.

There is one thing I would not recommend that is to add refrigerant. I would recommend setting high pressure switch set low to maybe 125 psi.

Most refrigeration engineers will recommend setting low pressure switch to prevent compressor shaft seal from seeing a vacuum and drawing in air.

[MoonlightSailor]

Thanks everyone for your input. I have not had the time to work on the system again yet since last week.

Will this belt tension gauge from Amazon work?
ABN Belt Tension Gauge - Universal, 10 lbs specification, Easy to Read https://www.amazon.com/dp/B01M2ZHHNX..._yPttAb5JJA42W

The electromagnetic clutch model that I have is Ogura ma-6a. Does anyone have any suggestions for the correct spanner wrench to purchase for removing the clutch from the compressor? I also have a call out to the manufacture of the clutch for suggestions regarding the spanner wrench and the bearings.

[MoonlightSailor]

Jammer, thanks for your product suggestions. I found this belt tension gauge on Amazon after re-reading your post. Will this one work ?

Gates 91107 Belt Tension Tester https://www.amazon.com/dp/B000MUTAGS/ref=cm_sw_r_cp_api_uautAbTHEVMFB

[Jammer]

The Gates 91107 tester is very similar to the one I have. Works by measuring the angle of deflection produced by the application of a known amount of force -- you push on it slowly and firmly until it clicks to tell you you've reached the required level of force. Then the little plastic wedge shows the angle but is calibrated in pounds of belt tension. They work very well and can be used in cluttered engine bays, and don't use up much room in your toolkit.

The ABN tester is larger and will measure the deflection distance when a 10 pound force is applied. It is useful for situations where the engine (or car) manufacturer specifies the tension that way. They are somewhat larger and require more clearance to use. You can convert between pounds of belt tension and the 10# deflection distance using some trigonometry if you know the length of the belt runs between the two pulleys.

[MoonlightSailor]

OK. Sounds good. I will order the belt tensioner gauge by Gates 91107

Any suggestions on the correct spanner wrench for the Ogura clutch model MA-6A?

[OzePete]

Originally Posted by MoonlightSailor

Greetings,

History of situation:
Tarawa - System developed a leak at the small copper tubing that connects to the high/low pressure switch. That was fixed and we recharged the system. I can't remember exactly how much R12 we put in the system but it was close to what we left San Diego with.

We returned to Hawaii and stopped using the system.

Upon trying to use the system to go on an interisland cruise, I found that the compressor (belt driven from a 3HP electric motor) seemed to be bogged down and the clutch on the compressor was slipping. I thought the clutch was bad but that was not the case because I switched clutches.

The compressor obviously seems like it has too much of a load on startup.

However, I am albe to engage the clutch and it will spin a few revolutions before the clutch starts to slip. I found that if I engage the clutch for a few revolutions and then turn it off when it starts to slip and repeat this process, I'm eventually able to keep the compressor running without slipping.

I'm suspicious that it is over charged. Suggestions are appreciated.

All refrigeration systems consist of a closed circuit within which the refrigerant travels / lives. Always, some of the refrigerant is in liquid form while some is vapour. Now during normal continuous use, the system is running and then off etc and the off cycle sees the refrigerant pressures 'balance out'. Unless a 'pump down' system, the liquid will mostly occupy the evaporator as that is usually the coldest area and unlikely to lay in the compressor as it is usually warm. (The refrigerant will settle as liquid in the coldest areas and vapour in warmer areas)
Your system's compressor locking up issue, having been off for a while, may
be the result of liquid laying in the compressor, specially if it is in a cooler place than the evaporator (cabinet). The real test of this possibility is to feel the suction pipe near the compressor (Largest pipe) as it tries to start. If after some revolutions you feel that the pipe is chilling then your poor old compressor is trying to compress liquid and they don't like that!
If you confirm that this is the problem, try warming the compressor especially the base. If this was the issue it should be ok once your cabinet is down to temperature and the refrigerant behaves itself as normal provided the refrigerant charge is correct and the TX valve is not faulty or stuck open. . Also, don't tighten belt until you are sure that there is no liquid being pumped otherwise you will only contribute to possibly destroying the compressor, and set your HP control cut out at at least 160PSI.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems