oil amount in mobile refrigeration system

[freezingfan]

Dear techs:

I have some background in commercial refrigeration systems as well as in domestic automotive air conditioning, but when it comes to tranpsort refrigeration I´m still in diapers.
I´ve been required to perform a compressor replacement job in a Thermo King CB max unit. The unit has both a engine-driven compressor as well as a electrically driven stand-by compressor. As I´m getting ready to pull out the old engine-driven compressor, two questions come to my mind: 1) why should the existing SELTEC TM-15 compressor be replaced with a TM-16 (as suggested by our senior technician), and 2) in regards to the oil amount required by this system, what should be the proper amount of oil for such dual-compressor/long hose system? We have no TK maintenace manual in our shop reference library, but I can figure out the oil required by each compressor from the compressor manufacturer´s data. Is this information of any use?. Thank you in advance for any helpful hints.

[absolute-zero]

Dear techs:

I have some background in commercial refrigeration systems as well as in domestic automotive air conditioning, but when it comes to transport refrigeration I´m still in diapers.
I´ve been required to perform a compressor replacement job in a Thermo King CB max unit. The unit has both a engine-driven compressor as well as a electrically driven stand-by compressor. As I´m getting ready to pull out the old engine-driven compressor, two questions come to my mind: 1) why should the existing SELTEC TM-15 compressor be replaced with a TM-16 (as suggested by our senior technician), and 2) in regards to the oil amount required by this system, what should be the proper amount of oil for such dual-compressor/long hose system? We have no TK maintenace manual in our shop reference library, but I can figure out the oil required by each compressor from the compressor manufacturer´s data. Is this information of any use?. Thank you in advance for any helpful hints.

When replacing the compressor you should record the amount you removed, and only put that amount back in. CB with electric standby systems take much more oil than a system that does not so, oil charging varies. But if you look at CB yellow maintenance manual spec section, It will give you instructions on how much oil is to be added to the Roadside compressor and also the standby compressor as well the additional amount to be added to receiver tank.

Seltec swash plate TM16 compressor is larger capacity than a TM15, however engine type that drives the compressor should determine compressor, as diesel engines typically run lower peak RPMs compared to a gas engine that can exceed 5000 rpms. Selecting the compressor for the application and give the unit best capacity and life is what your after. Ask your supervisor for a RPM sheet that clearly shows all the rpms for designed compressors.:)

[abbsnowman]

Gotta go with AZ on that one.
Also, if I am not mistaken, there is likely an oil seperator on that unit. Check that too. I have seen them plug and cause compressor failure. (It is also a filter)
Some other causes are condenser fan cycling switch not closing. Low refrigerant, (this realy plays a roll on the over the road system as high rpm of engine causes unit to run in a vac. and therefore pushes oil out and pulls moisture in.
Just some food for thought.
Please let us know what you find!:)

[absolute-zero]

Gotta go with AZ on that one.
Also, if I am not mistaken, there is likely an oil seperator on that unit. Check that too. I have seen them plug and cause compressor failure. (It is also a filter)
Some other causes are condenser fan cycling switch not closing. Low refrigerant, (this realy plays a roll on the over the road system as high rpm of engine causes unit to run in a vac. and therefore pushes oil out and pulls moisture in.
Just some food for thought.
Please let us know what you find!:)

Oh and dont forget to replace liquid injection orifice, that attaches to suction line at compressor. If system is a 134a it wont be present, but all max units will have it. If you fail to service or not install it, you will lose a compressor due to excessive liquid entering the compressor in high ambients.

[o5g]

Go with the TM16. Not sure how easy the condensing unit is to get to but if the old compressore cratered or the oil is black (make sure to also check the txv screen) and you don't have a VanSteenburgh or similiar unit to clean system up install a suction filter to clean up system. I have done alot of these and have installed the TM16 and they really improve performance. Road compressor is 11.5 oz and standby is 5.7oz. I am sure some will disagree but having abit too much oil is better than not enough with this type of system.

[abbsnowman]

Oh and dont forget to replace liquid injection orifice, that attaches to suction line at compressor. If system is a 134a it wont be present, but all max units will have it. If you fail to service or not install it, you will lose a compressor due to excessive liquid entering the compressor in high ambients.
Do you have High ambients were you are AZ? Hehehehe:D

[abbsnowman]

Go with the TM16. Not sure how easy the condensing unit is to get to but if the old compressore cratered or the oil is black (make sure to also check the txv screen) and you don't have a VanSteenburgh or similiar unit to clean system up install a suction filter to clean up system. I have done alot of these and have installed the TM16 and they really improve performance. Road compressor is 11.5 oz and standby is 5.7oz. I am sure some will disagree but having abit too much oil is better than not enough with this type of system.
You are part right but I have also seen too much oil in a system and it was very difficult to cure! Be careful!;)

[absolute-zero]

Do you have High ambients were you are AZ? Hehehehe:D

Abbs, we have extreme weather where I am from, thats right from one extreme to the next, and if you dont like it just wait 1 hour and it will change. The winter can be -20 degrees f, and the summer it can get over 100 degrees f, and because I live in great lakes along with finger lake region, the humidity can be just as high. We expiernce both situations here.

Units break in the summer just as much in the winter.:D

Now thats cash in wallet.

[abbsnowman]

Units break in the summer just as much in the winter.:D

Now thats cash in wallet.[/quote]
Love the way you think buddy!;)
3 peas in a pod

[absolute-zero]

Units break in the summer just as much in the winter.:D

Now thats cash in wallet.
Love the way you think buddy!;)
3 peas in a pod[/quote]

I knew you could appreciate that.:D