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Chiller Operation with 365kVA Genset

04/13/2014 8:25 AM

Hello Everyone,

We are having an operational issue while running the chiller on genset. The chiller in question is a 200 ton Mcquay PFS 200.2. Voltage Supply is 380V-415V,3Phase,50Hz. The genset is a CAT 365KVA Model number (C15 ATAAC, I-6, 4-Stroke Water-Cooled Diesel). Initially when the chiller was set up it ran flawlessly on both utility and genset supply. The chiller has two compressors each having a 60KW motor. In the beginning compressor one starts and draws about 322.3Amps and running current is about 98Amps. After sometime the second compressor kicks in. About 10 days ago the chiller developed a fault related to one of its oil switches after clearing the fault the chiller ran successfully on utility supply but as the compressor kicks in on genset supply the unit shuts off giving "Phase Monitor Alarm" on its LCD.

Phase Monitor on chiller panel has following settings

Upper threshold Voltage = 440V

Lower threshold Voltage = 370V

ASYM% = 8%

t = 0sec

time delay switch turned off.

When the compressor kicks in on genset supply the voltages at chiller terminals are as follows, L1 = 361V, L2 = 337V, L3 = 353V. While the voltages measured at the genset are L1 = 444V, L2 = 434, L3 = 360V. The voltages return to normal range of 404V, 402V and 407V in 2 seconds.

On second attempt following are the results,

Voltages at the chiller terminals - L1 = 325V, L2=349V and L3 =335V and the voltages at the genset are L1 = 361V, L2 = 362V, L3 = 368V. Same as before the chiller failed to run and gave a Phase monitor alarm.

However we turned on the time delay dip switch of the phase monitor with following settings and the chiller ran on genset.

Upper threshold Voltage = 440V

Lower threshold Voltage = 370V

ASYM% = 15%

t = 2sec

time delay switch turned On

However the chiller reps say that they have not even touched the phase monitor settings and the chiller was running on genset with default settings.

We are aware that during start-up voltage dip does occur and is more in a genset as compare to a utility source as it is more robust. However at the time when compressor kicks in the genset frequency goes down to 45Hz and sometimes to 44.6Hz. The chiller reps illustrates that the issue is with genset while the genset people states that there gesnet is perfectly fine. The chiller reps say that they will not change the settings of the phase monitor until they receive an approval from their manufacturers in china. The claim that the genset for some reason is not able to able to provide sufficient output voltage for the motor so that it can develop adequate torque to accelerate the load to rated speed.

I know the material is very long but any suggestions would be highly appreciative.

Regards,

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#1

Re: Chiller operation with 365KVA Genset

04/13/2014 8:55 AM

it sounds like your chiller controls are doing exactly what they're designed to do. they are protecting the unit from "dirty voltage". I'd look closer at getting your supply (genset)to hold a tighter band on frequency output being supplied to your load(chiller) as the frequency changes so will your net voltage

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#2

Re: Chiiler operation with 365KVA Genset

04/13/2014 9:09 AM

I go with Fredski, find out why your frequency drops 10%, fix that, and your problems will most likely be solved. As an aid to that, learn what the exact parameters are that cause your Phase Monitor to trip, and also check the settings on your governor/speed control.

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#3

Re: Chiiler operation with 365KVA Genset

04/13/2014 9:51 AM

My apology in advance. From the testing and commissioning point of view of your Genset voltages does seem to show variation a little. I think it must remain between 5%? But it does seem to operate fine. There could be many many issues, starting from the cable run to the chiller unit. A voltage drop could be a factor at start up. We must calculate Vt at start up. I may be very wrong to assume that there could be a problem with the chiller, but then again a mechanical engineer could better figure it. Sorry! Check the earthing and the neutral system as well by testing it. etc.

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#4

Re: Chiiler operation with 365KVA Genset

04/13/2014 9:53 AM

Thanks Fredski and RAMConsult.

When this problem first appeared a technician from CAT visited the site and he said that there seems to be a mechanical issue with the genset as when he tested the genset by increasing the load from 135Amps to 250Amps the frequency dropped to 48.9Hz and at 135Amps it was 49.3Hz. He said the frequency should be close to 50Hz like should be 49.9Hz or 49.8Hz. However when the mechanical technicians visited the genset during my lunch time he concluded that the genset is flawless and its the phase monitor settings which are too sensitive.

About 5days ago when the chiller was out of order due to the oil switch problem. The genset was supplying power to the building when suddenly there was a major drop in voltage and the pumps started making abnormal noises while few of the pumps tripped. By the time we reached the LT room everything was normal. We asked the genset people and they said it was nothing.


The genset technicians are visiting the site tomorrow and will get back with more details.

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#5
In reply to #4

Re: Chiiler operation with 365KVA Genset

04/13/2014 11:10 AM

Has your genset been tested with load bank prior to delivery to your site? What is the length between the source (genset) and the chiller unit? If not the cable size? I would like to calculate, if I could, the ideal theoretical voltages at your chiller compressor/motor terminal and possibly compare to your tested and measured voltages recorded above? Thanks!

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#6
In reply to #5

Re: Chiiler operation with 365KVA Genset

04/13/2014 12:05 PM

Thanks abasins. We did asked them if the genset has been subject to full load test and unfortunately the reply was no we did not. In their defense they said its a CAT made generator not much can go wrong with it. :-0. The distance from the genset to LT Panel is about 100 meters. Sorry I dont remeber the cable size though. The distance from LT panel supplying to MCC1 in plant room is about 45m and cable size is 185sqmm. Distance from MCC1 to chiller panel is 20m and cable size is 185sqmm.

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#8
In reply to #6

Re: Chiiler operation with 365KVA Genset

04/13/2014 1:29 PM

My apology again! I found all your data within the allowable calculated values. Everything seems fine. I am having no idea whatsoever where the problem would lie, in fact when the voltage at the chiller's compressor terminals during starting to be calculated 320 V. That's what almost your data is having. I found your cable size to be a little over sized though but that should not be a factor though? Good luck buddy. If you want I could put up the lengthy calculations I did for you but I suggest not to for the sake of saving bandwidth...Hahahaha...

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#7

Re: Chiiler operation with 365KVA Genset

04/13/2014 1:13 PM

The frequency drop suggests a possible governor or fuel delivery issue. Check for plugged fuel filter, water in fuel, or air being sucked into fuel line.

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#9
In reply to #7

Re: Chiiler operation with 365KVA Genset

04/13/2014 1:30 PM

Thanks Tornado! That might be it?

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#11
In reply to #9

Re: Chiiler operation with 365KVA Genset

04/13/2014 10:03 PM

Maybe, but I am still wondering about the voltage imbalances and drops between the genset and the motor terminals. Bigg may also be right.

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#10
In reply to #7

Re: Chiiler operation with 365KVA Genset

04/13/2014 1:31 PM

He might also check the air cleaner/filter.

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#12
In reply to #7

Re: Chiiler operation with 365KVA Genset

04/14/2014 12:58 AM

When Op mentioned the other subnominal manifestation (complaining pumps) that's where my thoughts were wandering to as well.

A subsequent poster has mentioned a possible blocked air filter....something may have taken up residence in the can.

A turbo charger may be on the blink too.

But yeh, donk problem not electrical.

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#13

Re: Chiller Operation with 365kVA Genset

04/14/2014 9:09 AM

Yes, the pump problem gave us the clue that its not a chiller problem, its a genset problem. 185mm^2 cable seems ok sized. A 365KVA genset should be able to supply 560A/3φ at 220/380v at 100% pf. Why cant the generator hold its frequency? Clearly the generator isnt doing what it should.

Ok so what are the possible solutions?

1. fix the generator, 2. go with the the 2 second time delay, or 3. soft start.

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#14
In reply to #13

Re: Chiller Operation with 365kVA Genset

04/14/2014 9:38 AM

Start easy.

Check the service records for the donk. If they exist. Yeh, you get that.

Start checking the filters. That's easy enough.....then....

Visually and aurally (maybe tactile as well with care) observe the genset when the chiller tries to start..it may give a clue. The turbos should be whistling. The donk should roar to life not fart and falter. Have someone observe the stack for black smoke puffs as well. If you are in low light a slight turboglow is a good sign.

It does have oil, right?

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#15

Re: Chiller Operation with 365kVA Genset

04/16/2014 5:37 AM

Hello everyone,

Sorry for the late reply. I was down with fever. Secondly thank you very much for your valuable suggestions. The genset people inspected their unit on Monday and found out some issues with their engine governor. After some tweaking we switched the chiller on but unfortunately it failed to start with time delay switched off. The voltages at genset were 389V 386V and 383V (During Torque Load) while the voltages at chiller terminal were 362V, 382V and 375V. However when we turn ON the time delay it works. The difference is that the ASYM value has come down from 15% to 8% on the Phase Monitor. The frequency at torque load was 49.1Hz.

We are still investigating the matter and will let you know as more information pools in. In the meantime we are open to suggestions.

Regards,

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#16
In reply to #15

Re: Chiller Operation with 365kVA Genset

04/16/2014 6:27 AM

....In their defense they said its a CAT made generator not much can go wrong with it...

Seems they, the genset folk, were wrong then.

To their credit they seem to be responding proactively.

Watch them real carefully and learn as they learn.

Take lots of photos and video with audio....

I'd be asking the genset folk to perform a full (re)commissioning.

Do you still owe them money?

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1capybara (1); abasins (4); bigg (1); Fredski (1); RAMConsult (1); Rookieengg (3); Tornado (2); Wal (3)

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