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dogma
31-01-2010, 04:25 AM
Hey guys, wondering if I could get some advice about a situation I have at the moment....I have a tecumseh 3 Phase recipricating Compressor Model Tagp2516z which was a replacement for a Copeland Scroll Model ZF13K-TSV-556. I changed from the Copeland to the Tecumseh as the Copeland had been running inefficiently. Upon connection of the Tecumseh Compressor I noticed the Phase Rotation was incorrect(for the Copeland Scroll). I performed acid tests for the oil, no acid was present, tripple vacced the system and charged with R404A. The compressor ran fine until it reached -17 degrees then struggled to hold that temperature. Suction pressure was -35 degrees C, ambient teperatures were 38 degrees C, and condensing pressure was at 52 degees C. The coldroom ran for 1 week and the new compressor has now failed resistence betwwen L1 and L3 and has failed to earth.

Upon further inspection, a newly commissioned 3 Phase generator was auto swiching on mains power failure and was noticed to be switching phases(L2, L3 - opposite to incoming power supply) with a delay time of no more than 30 seconds.

Has this caused my compressor failure??? Please help as this is URGENT!!!

Chillin4alivin
31-01-2010, 10:23 AM
Not sure if i can help but running a generator instead of mains power can often cause problems with compressors on start up...is it possible to isolate the generator from your kit until you replace comp and have it running on trial?

glenn1340
31-01-2010, 11:42 AM
Just and idea here. If the genny had kicked in automatically on power failure maybe the high and low pressures in the compressor hadn`t had time to equalise (or any where near equalisation) thus causing it to overload. Was the overload matched to the new comp?
I seem to remember that scroll comps are more tolerant of reverse running but I wouldn`t like to put a tenner on it.
If there is a danger of this happening again with a power outage maybe fitting an auto restart with a timer to allow equalisation would be an idea.

Regards,
Glenn

Yuri B.
31-01-2010, 12:06 PM
Was the direction of rotation of the oil pump correct ? Oil pressure diff relay set correct ?

chemi-cool
31-01-2010, 04:50 PM
Tagp2516z is a small hermetic compressor.

There is no way you can tell the rotation direction. Only after start up. There is no arrow to indicate the rotation.

Therefore the sequence of the phases has absolutely no importance.

NoNickName
31-01-2010, 04:56 PM
Infact no matter what is the rotation, hermetic and semihermetic compressors can operate in both directions. Scrolls are different story altogether.
But, the genset surely spikes when kicks in, and a high voltage transient can pierce the insulation laquer.

VRVIII
31-01-2010, 05:43 PM
Hi,

Iíve heard of previous scroll compressor failure due to back up generators being wired with a different phase sequence (but never a recip compressor). Units with scroll compressors have reverse phase protection devices, however the reaction time of the protection device wasnít quick enough to detect the change in phase sequence. The generators will kick in fairly quick and most devices only check phase sequence when power is applied but will detect a phase failure.

This raises an interesting question,
How would a reciprocating compressor react to a phase sequence change during operation?
Obviously if the compressor stopped it would then be attempting to start against high pressure (no time to equalise).

chemi-cool
31-01-2010, 05:52 PM
When rotation direction is critical, a phase sequence relay must be installed to protect the compressor.

chemi-cool
31-01-2010, 05:56 PM
This raises an interesting question,
How would a reciprocating compressor react to a phase sequence change during operation?

It Will break into small pieces......

VRVIII
31-01-2010, 06:03 PM
When rotation direction is critical, a phase sequence relay must be installed to protect the compressor.
I agree, but as I said most reverse phase protection devices will not detect a change in phase sequence during operation.
Example: back up generator kicking in during operation, power on/off/on is quicker than reaction time of protection device.

glenn1340
31-01-2010, 06:11 PM
Hi,


This raises an interesting question,
How would a reciprocating compressor react to a phase sequence change during operation?
Obviously if the compressor stopped it would then be attempting to start against high pressure (no time to equalise).

Well, on a large recip you could have the problems with trying to reverse a large rotating mass ie massive strain on a coupling or shredded belts.
On a small recip I`d have though an overload relay should protect the motor
This why I`d suggest a auto restart facillity if power outage could cause problems on a critical system.

VRVIII
31-01-2010, 06:21 PM
Well, on a large recip you could have the problems with trying to reverse a large rotating mass ie massive strain on a coupling or shredded belts.
On a small recip I`d have though an overload relay should protect the motor
This why I`d suggest a auto restart facillity if power outage could cause problems on a critical system.

Cheers Glen, I totally agree :D:D:D
BTW if a scroll compressor is operated in reverse it will rapidly overheat and kill compressor ;)

cadwaladr
31-01-2010, 06:57 PM
when you replaced the compressor,did you replace contactor and o/load, what reason for initial compessor failure mechanical/electrical,seen many second failures due to contactors so i always change em also seen a lot of guys change single phase hermetics and never fit the new electrics that are supplied with em?

monkey spanners
31-01-2010, 08:53 PM
A lot of hermetic compressor run around 2900rpm, i wonder how quickly the changeover is and if its gone from clockwise to anti clockwise a few times and snapped something, nearly a 6000rpm difference!
I wonder as the scroll has an orbiting motion if it would have as much inertia, also the tend to want to spin backwards when they stop so this would help in a way.

chemi-cool
31-01-2010, 09:19 PM
There must be a simple way to protect the electrical system and the other components from turning back wards when a generator comes in.

I am seeing tomorrow a person from the national electric company for connecting a 5 MW solar system and I will ask him about that protection.

VRVIII
31-01-2010, 10:07 PM
There must be a simple way to protect the electrical system and the other components from turning back wards when a generator comes in.

I am seeing tomorrow a person from the national electric company for connecting a 5 MW solar system and I will ask him about that protection.
The generator out put should be tested and ensure this has the same phase sequence as mains supply.

NoNickName
01-02-2010, 08:43 AM
It shouldn't kick in at once. Generally, a bank of batteries connected to a three phase UPS should provide seconds to minutes of back up, while generator settles.

dogma
01-02-2010, 10:05 AM
Tagp2516z is a small hermetic compressor.

There is no way you can tell the rotation direction. Only after start up. There is no arrow to indicate the rotation.

Therefore the sequence of the phases has absolutely no importance.

Hi mate. I have a rotation analyzer and it does have a little arrow :). It's placed across the incoming phases to indicate clockwise or anti clockwise direction.

...But the real issue I face is, if the compressor stops, for 30secs to 1 min, then starts with reverse rotation, then instantaneously reverses back to correct rotation whilst still running, when the genset drops out, will this have a dramatic effect as I've seen in this instance?????

BTW there is no battery bank on the genset.

lowcool
01-02-2010, 12:33 PM
its poor windings,apart from that my opinion is that they should work in a bucket of water

dogma
01-02-2010, 02:03 PM
...... More info........... When the motor grounded, most of the oil blew out of the compressor back up the suction line. the contamination has been localized to the compressor sump, suction line and accumulator. No acid.

chemi-cool
01-02-2010, 05:30 PM
We had a long discussion about that issue.

What they do is very simple,
After the main switch, [Isolator in UK] there is a sequence relay that operating a control relay or a small contactor.
If mains falls and generator kicks in, there is momentary cut out of the electricity, when it comes back from the generator, it goes through the same control circuit and it takes for that sequence relay Ms to check the phase sequence. If all OK, it will start the control circuit.

And therefore there no way the compressor will change its rotation direction.

I hope you all understand what I mean.

imran ansari
01-02-2010, 05:56 PM
you not mention there is timer or no?
in three phase less chane compare to single phase

dogma
03-02-2010, 02:58 AM
We had a long discussion about that issue.

What they do is very simple,
After the main switch, [Isolator in UK] there is a sequence relay that operating a control relay or a small contactor.
If mains falls and generator kicks in, there is momentary cut out of the electricity, when it comes back from the generator, it goes through the same control circuit and it takes for that sequence relay Ms to check the phase sequence. If all OK, it will start the control circuit.

And therefore there no way the compressor will change its rotation direction.

I hope you all understand what I mean.

I understand what you are saying chemi-cool, but the the situation remains that when the genset was commissioned, it wasn't commissioned correctly. We had a call out to a cold room at the same location as the phases had been reversed and therefore the compressor on that system was running loud and inefficient. once the generator power dropped out, the compressor began working again... this was a scroll type. After this was noticed the commissioning electrician returned to correct the phase issue with the genset.... 3 days later the reciprocating compressor grounded.