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Thread: Those Chillers are Rubbish!
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18-09-2009, 10:19 PM #1
Those Chillers are Rubbish!
Ever had it said?
OK.
Now I am going to tell you a story!
I hope you are sitting comfortably?
Recently I arrive on-site to carry out what I believe is a scheduled Maintenance Visit.
On 2 Modern Chillers mounted on a large Office Block roof. These are connected to the Trane BMS via the normal remote run signals.
On arrival I notice several vehicles from the Facilities Company that "we" are contracted to.
( Normally the site is only visited by 1 of their engineers once a week.
And we are contracted to 4 visits a year.)
So I contact the Office Block representative who is responsible for any Contractor whilst they are on-site.
I am met at the door by this young lady.
Who says "Oh Good, have you come to fix the Chillers?
They have become a real pain as they are always breaking down lately.
This comes as somewhat of a surprise to me!
Because although the chillers are made by a rival company.
They are non the less very good and reliable.
I also knew from my previous visits that they are well over sized and therefore more than capable of handling any loads required of them.
In fact normally only 1 of the 2 chillers ever ran at any given time!
So I answered.
That although i was only supposed to be carrying out a "Maintenance Log".
I would be more than happy to investigate their problem further.
When i get to the rooftop Plant room.
Which houses the Boilers, Air Handling Units, Chilled Water Pumps etc.
With the 2 chillers Just outside through a pair of double doors.
I meet a Controls Engineer from the Facilities Company with his laptop connected via the Trane Outstation.
We will call him Dave ( because I cannot remember his real name.) Dave turns out to be one clued up guy and helpful with it.
So we get to talking:-
The initial diagnosis is that periodically an engineer will be called to site to investigate loss of cooling to the 3 floors of offices.
He normally would find the Chiller Flow Fault alarm illuminated on the Main Control panel within this plant room.
This control panel controls every thing other than the chillers. Which it just sends a run signal to or indicates an alarm condition.
Resulting in a manual restart of the chillers followed by a reset within the main control panel.
Apparently one-time whilst resetting the system the engineer observed the whole of the main control panel lit up like a set of Christmas Tree Lights!
With all the indication lamps switching on and off before the panel locking out on Chilled Water Flow Fault.
My first action was to interrogate the chiller alarm history. I drew a blank sure enough flow switch failure was observed. but when checked the flow switch operated as it should.
I go back to Dave, who in the meantime has discovered that Trend is programmed so that once a week.
The running Chilled Water Pump is stopped and the 2nd one starts up. To balance the running hours.... Acceptable standard practise!
Only when he triggers the change over nothing happens. So I investigate further, only to find that the 2nd pump has tripped its MCB/Overload. Not sure how their engineers missed that one? The pump metered out perfectly?
Having reset everything Dave and I agree to go for another test run of the Pump changeover.
Pump changes over!
Suddenly the panel lights start flashing with cont actors chattering, it's the Christmas tree Lights all over again. pretty scary it is too!
Whilst all this is happening I noticed that over in the far corner of the plant room.
The small chilled water pressurisation unit was switching it's pump on and off. in unison with the Main Panel Lights and Contacts.
Eureka!
This unit had 2 circuits each with a pressure gauge and it's own pressure switch to operate the "top-up" pump.
Further investigation revealed that when the r/h circuit (which has a small leak) dropped to 1bar the pump switched on.
When the pump rose above 1bar it switched off!
No differential (factory set and unable to adjust without a major strip down).
So this tiny little pressurisation unit was causing the chilled water circuit pressure to fluctuate sufficiently.
That when the system pressure was low enough the flow switch paddle would flick back-wards and for-wards.
In time with it's pump which in turn was switching the main control panel and pumps on and off!
Hence the Christmas Tree Lights.
And Everyone said " THOSE CHILLERS ARE RUBBISH!"
"Thanks to Dave"
Him and I walked out of there feeling pretty happy with ourselves that day
GrizzlyLast edited by Grizzly; 18-09-2009 at 10:26 PM.
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18-09-2009, 10:49 PM #2
Re: Those Chillers are Rubbish!
Only goes to show that time spent fault finding is never wasted.
Passing the buck is so much easier though if "It's not my job mate."Brian - Newton Abbot, Devon, UK
Retired March 2015
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19-09-2009, 01:14 AM #3
Re: Those Chillers are Rubbish!
Well done to Grizzly & Dave. You can be proud of your achievements & off your professionalism.
Hat tip to you sirs...Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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19-09-2009, 08:15 AM #4
Re: Those Chillers are Rubbish!
Seems to become SOP to blame the chillers, or AHU's or whatever else instead of investegating what the real problem is.
We have a job site where we have a 6MW heating and cooling plant. In heat mode one chiller is running and satisfies the heat load of about 700 kW. Suddenly the chilled water entering temperature drops from 12 dgr C to 8. The chilled water valve opens to 100% and the pump speeds up to 100% but still the water keeps dropping. So the warm water temperature drops below setpoint. The systems will start a second chiller to satisfy the load, but no load is comming from the wells. So after an hour or so all four chillers are running and they all run at minimum load. Then all of a sudden the wells kick in and produce so much heat at once that all four chillers kick out.
They blame the chillers and the control panel that controls them for the problems and not the panels that control the wells, a third party, which causes the problem!
Ignorance is bliss!If it ain't broke, don't fix it!
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19-09-2009, 11:13 AM #5
Re: Those Chillers are Rubbish!
Thanks Lowrider, Brian and Desa.
My post is not to "Big Up" Myself.
Much as you imply Lowrider, it was mearly a good example of that old engineers problem.
Where the end user or those between are all to ready to blame your perfectly good equipment.
Often expressing total innocence on their part.
Yours is an interesting post and I can relate to it having had similar situations.
Usually involving independently controlled Variable speed pumps on the chilled water circuit.
Chillers Hate variable loads (fast response ones that is!)
In most cases we have had to resort to bespoke control software.
Anyway I hope it has been of interest to some?
Grizzly
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19-09-2009, 11:37 AM #6
Re: Those Chillers are Rubbish!
Well done Grizzly.
Remained me the stories of an RE engineer in an old British refrigeration magazine. Les something......was his name.
Its all comes down to the patients and common sense of the engineer.
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19-09-2009, 12:22 PM #7
Re: Those Chillers are Rubbish!
Understanding hydraulic layouts and controls of multiple chiller systems and the effects of load and flow variations are becoming more and more a problem because most people just don't understand. This trend will continue for years to come because most people are not able to see the bigger picture or willing to learn how.
I'm glad I'm not the only one dealing with these kind of things!
Good Engineers, in refridgeration, controls or both are getting harder to find each day!If it ain't broke, don't fix it!
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19-09-2009, 12:40 PM #8
Re: Those Chillers are Rubbish!
Good job. über par diagnostic abilities.
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19-09-2009, 01:25 PM #9
Re: Those Chillers are Rubbish!
Nice one! I attend a group of sites where a "consultant" advised fitting VSD's on all the chilled water pumps, after several months of nuisance trips the client finally agreed to get them back in and program them to run at full load all of the time, problem solved, but in those few months, I got all the grief, those chillers again etc.etc.
It seems that Bull**** baffles brains with a lot of these people.
CheersTutto il Mondo e un Paese
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20-09-2009, 12:31 AM #10
Re: Those Chillers are Rubbish!
Welcome to my world. and yes Trane chillers are ****e.
Takes a licking, keeps on ticking.
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20-09-2009, 09:24 AM #11
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20-09-2009, 10:43 AM #12
Re: Those Chillers are Rubbish!
Takes me back years ago to a problem I had on a screw air compressor that overheated off load, on load it was fine as you`d expect. The repair history was a parts suppliers dream, right down to the air end being overhauled. The switching thermometer had capillary tube had even been cut by some one so as not to give an indication of the compressors temp.
On thinking there must be a restriction in the oil circuit I removed the flexible pipes (on several oassions I`ve found the inner walls breaking up). All the pipes were ok but what I did find was the internal flashing on a cast 1" BSP fitting hadn`t been removed when the m/c had been built. The result was that when on load the pressure was enough to ensure adequate oil flow but off load the flow dropped enough to cause the compressor to trip. The flashing being removed the compressor ran fine.
As Grizzly states allways expect the unexpected.
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25-09-2009, 11:10 AM #13
Re: Those Chillers are Rubbish!
Any of you guys worked on any LG VRF ?
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25-09-2009, 11:31 AM #14
Re: Those Chillers are Rubbish!
Any Comments on LG VRF equipment
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25-09-2009, 05:49 PM #15
Re: Those Chillers are Rubbish!
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25-09-2009, 10:47 PM #16
Re: Those Chillers are Rubbish!
Also Welder, please learn a little patience.
Brian - Newton Abbot, Devon, UK
Retired March 2015
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26-09-2009, 02:12 PM #17
Re: Those Chillers are Rubbish!
Top effort Grizzly, it gives a greta sense of satisfaction finding long standing issues like those.
...and she said "give it to me you big fridgie"
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26-09-2009, 03:50 PM #18
Re: Those Chillers are Rubbish!
Thanks 750 valve.
Interestingly enough as the required repair need has yet to be authorised Via the facilities Co. We work for and then to the Building owners.
Myself and Colleagues are still getting periodically called out for Chiller flow alarms!
Never mind eh!
Cheers Grizzly
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30-09-2009, 06:50 PM #19
Re: Those Chillers are Rubbish!
as said before welcome to my world this is so familiar
allways blame the hardware never the operator!!
no such thing as bad units just a problem of bad techs!(mostly)
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05-10-2009, 02:03 AM #20
Re: Those Chillers are Rubbish!
HI all,
New here, I am a BMS engineer and Grizzly, we both live in Somerset if you ever need a hand with BMS.
The man you met Dave, was he old by an chance?
What building was it, I may just know him.
Cheers
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05-10-2009, 07:33 PM #21
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06-10-2009, 03:04 PM #22
Re: Those Chillers are Rubbish!
Good stories chaps.
Here's one I had recently - we lost the maintenance contract so it's back with the co. who installed the below :
This site apparently has a history of losing compressors. So badly, that the solution was to fit oil separators (R22 A/C designed plant, so theoretically no need if the velocities were ok afaik) and every safety kown to mankind. Plus EEV's in place of the original TEV's. Plus Innotech control system.
Now, as far as any of us could make out, a lot of the new Innotech system (NOT done by innotech, who I've always found helpful & useful) seems to duplicate stuff that's been left in the original control panel. No wiring diagrams of course, and the new stuff is in it's own MSB, making tracing cable even more of a nightmare. (Why you'd want or need 2 relays for everything is beyond me.) Additionally, the EEV's are controlled locally & are not effectively interlocked with the control system.
Packs are Bitzer tandem with G6 comps.
Main problem is that the Innotech isn't monitoring compressor faults, so the end result of any lockout fault with the compressors is wide open EEV's, and liquid refrigerant pooled in the evaporator.
Naturally it was all political, so no, I didn't get it fixed.
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06-10-2009, 07:16 PM #23
Re: Those Chillers are Rubbish!
Sounds a nightmare FreezerGeezer.
You definitely lost me somewhere around Innotech System.
Is this an Oz based company?
Or is it because I have led a sheltered life?
Cheers Grizzly
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06-10-2009, 10:03 PM #24
Re: Those Chillers are Rubbish!
Sorry Grizzly. Yes, they're a local BMS firm. Very successful, the local answer to Trend.
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03-11-2009, 06:59 AM #25
Re: Those Chillers are Rubbish!
I've got a better one. AT&T in USA..."chillers don't work reliably or efficienty". Further investigation found DP switches inop as well as a pair of welders goggles clogging the chilled water line.
Here is another. Smardt chillers shipped to site with Nitrogen charge for field install of contractor supplied R134A. Chiller could never meet full load on real hot days. The leaving chilled water would creep up to 50 degrees and higher. Owner was furious thought the chillers were junk. Factory called in and refrigerant tested; problem was contaminated refrigerant. Removed and replaced refrigerant and chiller is now the best thing to hit this industry since global warming.
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