Compressor acting strange refrig/freezer

Update. The unit tried starting after the thermostat warmed up again but this time stayed at 8.6Amps and then the thermal protection device tripped. So it seems like the compressor can start some of the time but not everytime. Why don't I see the LRA of 20Amps if the rotor is locked? All I see is 8.6Amps, a starting current but not a frozen rotor current yet it does appear to be frozen right now. I'll put a fan on it and try once its cooled off then keep you posted.

OK After 10 minutes with a small muffin fan blowing on it, it started OK and is now running. Is this just a nearly worn out compressor and an unfixable situation or is there something else I should do?

First thing you need to do is get more beer.

Yes, did that and have them in the back up fridge.

Hey John,

What type of thermal protection device is tripping? On the unit I assume? Could this be defective?

Are you sure about the capacitor value?

What ever you do, don't let those 4 beers go to waste

When the compressor is started after a long off period the pressure of the refrigerant is balanced and presents only a moderate load to the compressor motor. Once it starts cycling on and off the pressures are not balanced and the compressor now has the additional load caused by the high-side pressure. This causes the motor to stall due to lack of starting torque. Apparently this motor has no starting capacitor so the next thing to check is the R-134 charge and the high and low side pressures. Sounds to me like there could be a restriction in the refrigerant loop, expansion valve, the drier, or an improper refrigerant charge.

ps- the coiled line is the capillary tube that senses the temperature on the low side of the expansion valve and controls the refrigerant flow though it. If none of this makes sense then it's time to get a qualified refrigeration mechanic in there.

I understand all of this. This motor does have a starting capacitor which checked out OK using a Fluke 189 DMM in the cap scale. It reads 315 microfarads and the value stamped on the body is 270-324 from 110VAC to 127VAC The only thing the Fluke tester doesn't verify is breakdown voltage but at least the value reads promising as opposed to open or short or a hugely different value.

The thermal trip device has the name "COMPELA" stamped on it and is made in Brazil. It's cyclindrical in shape about 1" in diameter and 3/4" long and has a threaded screw in the center with a squared off head that looks like it could be adjusted. I haven't tampered with this yet. Should I tweak it upwards if it is adjustable?

I've been reading a lot of A/C tech notes and noticed that they use a special capacitor for hard to start compressors. Should I get one of these capacitors? What value do I need? I have a lot of capacitors in my shop so should be able to find one. Also, many of them say that unless the gas has leaked out from something like a knife in the evaporator its almost never a gas problem. Since this unit has never been touched since new and no apparent leaks have ocurred I tend to think it isn't a gas related problem.

I'm going to check the thermal device which is tripping at 8.6Amps although I feel it is working correctly. The thermal trip device has the name "COMPELA" stamped on it and is made in Brazil. It's cyclindrical in shape about 1" in diameter and 3/4" long and has a threaded screw in the center with a squared off head that looks like it could be adjusted. I haven't tampered with this yet. Should I tweak it upwards if it is adjustable?

Sitting in front of the compressor and observing a normal start up I see 9 to 10 Amps starting current then it runs. On failed start attempts it thermally trips and I see the 8.6Amps steady for 3 or 4 seconds then a trip ocurrs which I think is correct operation since the compressor seems stalled and needs to be disconnected or it will burn up. Since the inside of the refrigerator is cold it takes about half an hour or more between start attempts. Shouldn't this be enough time for the gas pressures to nearly equalize?

Ever since placing the fan yesterday it ran normally all afternoon so the conclusion for now is that the compressor needs to be cool for the restart to happen. It's the WHY I don't understand. It was off last night so I'm going to try it again right now and I keep everybody posted.

Regards

John

John,

I can't advise you on adjusting the existing thermal overload. I am not familiar with this particular brand. I did a Google search and was not able to find anything informative as far as adjustment.

If you know or if the amperage is stamped on the body of the overload somewhere, personally, I would replace it. To me, this is the simplest, least expensive place to start.

Next I would look at the capacitor.

I am by no means a refrigerant tech but if I was trouble shooting this for myself, I would take this route.

Keep us updated with the results!

Latest input: The freezer/refrigerator is 166litres, a small unit. The inside and outside temperatures today were 75F. Using the Fluke 189 and the amprobe I started the unit seeing only 5.5Amps start up current (all night off so refrigerant equalized). Using the Fluke 80T-IR temperature probe and a thermometer inside the box and a stop watch I collected the following data.

At 7 minutes IT (Inside Temp)= 55F, OP (Output tube from compressor)=122F, IP (Input tube into compressor from evaporator)= 84F, CB (compressor body around center)= 95F

At 10 minutes IT= 50F, OP=131F, IP= 87F CB= 113F

At 20 minutes IT= 42F, OP=145F, IP= 95F CB= 125F

At 25 minutes IT= 35F, OP=154F, IP= 97F CB= 135F

At 30 minutes IT= 33F, OP=159F, IP= 99F CB= 138F

At 32 minutes IT= 30F thermostat shut unit down.

At this point I turned on the muffin fan to start cooling the compressor body. I'll check the next start up and get the data.

For you experts out there how do those temperatures look??

Thanks (the beer will now get frosty and here in the Dominican Republic they call a frosty beer "vestida de novia" which means dressed in white like a bride, hehehe) I just hope I don't get too S--- Faced for the next data collecting session.

John

John,

Check out this web site:

http://www.tecumseh.com.br/pdf/TH345GS-et-01.pdf

Regards - KJK

CR4 Admin: updated website address 12/28/2018

Thanks. The first site was good but didn't have the 115V model I have. Estimates required. I'm having trouble opening the 2nd site.

The second one is a Google search with 598 results.

Some are in a language other than English but most non-English site have a "translate" option next to the link that will translate the site to English for you.

That is all I have for you on this my friend, I'm out.

Good Luck!

Thank you. I've concluded its an overheating issue. It's been running fine all day now with the muffin fan. Hope somebody might say a bit about the special capacitor and the temperatures I recorded.

Best Regards and Thanks to all

John

Something that hasn't been mentioned is voltage at the motor terminals during the failed starts. If the motor is fed through a long extension cord or there is corrosion in any of the electrical connections from the supply panel to the motor you could have sufficient voltage drop to reduce the starting torque to too low a value. If not then the "hard to start" capacitor may be your answer.

Thanks RAM. The voltage is good. I build my own extension cords using 3-12AWG and nice hefty Leviton plugs but I checked the voltage anyway with the Fluke and it only drops to 116 on start ups. What size capacitor is used for hard to start situations?

John

Hi John,

Glad to see that you have checked out the obvious so I did some more checking. It turns out that you have a PTCSIR motor. Look at this article

http://onecool-refrigerationservice.blogspot.com/2010_04_01_archive.html

and then look down for the the PTCSIR motor connection diagram. You will see that the motor type doesn't have a capacitor but others in this series do. Also the diagrams will assist you in further troubleshooting. In particular check the start winding (CS) for continuity and the PTC (Positive Temperature Coefficient) relay for proper action. I suspect that if the start winding is ok then the PTC relay may be releasing to soon; i.e., once it gets hot then it may open the starting winding connection before the motor develops enough torque to overcome the refrigerant back pressure. Hope this helps.

Alan

Ok, Thanks Alan, I'll check out that site. I took a picture of my wiring diagram and am trying to attach it here. You will see the capacitor called "capacitor de arranque" which is spanish for Starting Capacitor. Now lets see if I can figure out how to attach the diagram.

I was unable to attach. Sorry

John

John,

After you check out the site let me know which of the diagrams reflects what you actually have since there seems to be a discrepancy between the part number and your unit.

Alan