Internal Compressor Issue?

[Shooter Trouble]

I am working on a Trane rooftop condensing unit. I found the oil pressure switch jumpered out (no by me). The switch was bad, so I replaced. At the same time, I saw no oil in the site glass, but this system is know for its "oil traps", due to poor piping installation. I went ahead and added almost a half gallon of oil, just to be safe. There are no apparent leaks in the system, so the oil should be "out there somewhere".

Refrigerant pressures look fine as well, but the compressor locks out after 10-15 seconds, on amperage overload. It runs about 100-115 amps at startup w/a lockout of 107.

I'm guessing that I have some mechanical issues inside the compressor, but I am stumped. Is there an internal oil pump? Would the high amperage be a result from this if there is one?

Any advice is greatly appreciated.


Specs:
Trane
M# RAUCD104BC032BD1
RLA = 77 amps

[Lowrider]

What model compressor is in there?

A recip has an internal oil pump running off the crank.

If the oil diff switch has been tempered with it's possible the oil has gone to the evap and left the compressor running without oil.

Why, when it's a known issue, haven't there been any measures taken too correct the piping problems? Or is the piping correct but is the txv at fault or is the machine left running in low load for extended time?

[Shooter Trouble]

It is a recip.

As for why the piping has not been corrected....
I am just an underpaid tech working for a University that never "has any money" and will take someone elses opinion that DOES make more money (unless it costs them money to fix it). I'm sure you've heard that story.
ha!

I'm sure it has been starved of oil and the bearings have been damaged. You can hear the difference between the 2 compressors and the amperage draw is the topper.

I just hate to "call in the crane" if it can be salvaged (by someone that gets paid more than I do, of course).

Thanks for your response.

[Lowrider]

Just call Trane and let them have a look and see if the compressor can be overhauled or if they can get an overhauled compressor fitted. Let them also do a complete diagnostic of the machine to get a decend status from the guys who kno these machines!

[taz24]

I am working on a Trane rooftop condensing unit. I found the oil pressure switch jumpered out (no by me). The switch was bad, so I replaced. At the same time, I saw no oil in the site glass, but this system is know for its "oil traps", due to poor piping installation. I went ahead and added almost a half gallon of oil, just to be safe. There are no apparent leaks in the system, so the oil should be "out there somewhere".

Refrigerant pressures look fine as well, but the compressor locks out after 10-15 seconds, on amperage overload. It runs about 100-115 amps at startup w/a lockout of 107.

I'm guessing that I have some mechanical issues inside the compressor, but I am stumped. Is there an internal oil pump? Would the high amperage be a result from this if there is one?

Any advice is greatly appreciated.


Specs:
Trane
M# RAUCD104BC032BD1
RLA = 77 amps

Hello.

if it has an oil switch it will have an oil pump.
The switch needs a posative oil pressure to keep the comp running. If the oil is not in the comp the pump can't pump it and the oil pressure switch measures the difference and stops the comp from running therby protecting it. Sombody shorts out the switch rather than sorting the problem then allows the comp to run with no oil.
If this happens for long enough the comp will fail.
Maybe it is pure coincidence that it has siezed up at just the same time as you looked at it.

Cheers taz.

[Grizzly]

I am working on a Trane rooftop condensing unit. I found the oil pressure switch jumpered out (no by me). The switch was bad, so I replaced. At the same time, I saw no oil in the site glass, but this system is know for its "oil traps", due to poor piping installation. I went ahead and added almost a half gallon of oil, just to be safe. There are no apparent leaks in the system, so the oil should be "out there somewhere".

Refrigerant pressures look fine as well, but the compressor locks out after 10-15 seconds, on amperage overload. It runs about 100-115 amps at startup w/a lockout of 107.

I'm guessing that I have some mechanical issues inside the compressor, but I am stumped. Is there an internal oil pump? Would the high amperage be a result from this if there is one?

Any advice is greatly appreciated.


Specs:
Trane
M# RAUCD104BC032BD1
RLA = 77 amps

ER Something does not ring true here.
Unless the Model number is incorrect (read the attached data sheet)

According to Trane they are Scroll with internal oil pumps.

Shooter trouble may I suggest you get a Fridge Engineer in to look at it.

Because although the data gives lots of info.
I am reluctant to "talk you through it"
Sorry
Grizzly

[Lowrider]

You're right about the compressors, they are scroll's, but they don't have an oil pump!

A known issue with these machine's is loss off oil due to undercharge. If the pipes are not designed correct, ie no oil taps and the machine is left running in part load (just 1 compressor) for a long time the oil accumelates in the evap and will block the refrigirant flow back to the compressor and cause low pressure alarms.

My guess is the pressure switch that was replaced is the suction pressure switch.

Locked rotor amps for the smaller compressors is 117 A, for the larger ones 178 A. Rated load amps for the small ones 18,1 A, the larger 26,3. So 77 Amps is too much anyway!

Just Call Trane and ask for a new compressor, it's not that much work, about 2 or 3 days!

[Grizzly]

Lowrider.
You may be correct it's just that I read the description 2/3 the way down on the middle column.
Of the middle atttachment.


Have I read it incorrectly?
That aside I agree entirely!
Cheers Grizzly

ps That is quite a common fault with lots of chillers at low load, is it not?

[Shooter Trouble]

It may be a scroll, I agree, but the switch that I replaced was the oil pressure switch, for sure. A low pessure switch isn't labeled "suction & lube". I have no idea how long it's been jumpered out, but I'm sure it was for all of the wrong reasons.

I am a controls man, I'm just not confident once I get into the compressor itself.

At the right end of the compressor there seems to be a "bell" where there may be an oil "slinger" or pump, I'm not sure. It may be too late to even investigate this?

[monkey spanners]

What does the compessor look like?

Big smooth vertical tube with a couple of pipes connected=scroll (unless its one of those huge copeland dual scroll which are cast iron, unlikely)
Big cast iron job with a lot of bolted on inspection plates, cylinder head/s, cooling fins=semihermetic piston compressor, the type that would have an oil diff switch.

Jon

[Lowrider]

Lowrider.
You may be correct it's just that I read the description 2/3 the way down on the middle column.
Of the middle atttachment.


Have I read it incorrectly?
That aside I agree entirely!
Cheers Grizzly

ps That is quite a common fault with lots of chillers at low load, is it not?

Low load is indeed a common way to lose the oil. In this case even more because it's known that calculating the pipe sizes and the need for oil traps still is difficult for a lot of people.

Attached an drawing of an open scroll, an old one and a new one!