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dave hammo
24-12-2008, 09:38 AM
gday folks,having problem with proper loading of mcdaikinscrew comps high ambients(43c) panel says comps fully loaded 100% drawing170amps but fla 280 only4-5c td across evap 16c chw in 12chw out hp ok suction superheat 5c ex valve only open 550 steps out of possible 2600 would slide valve positioning require recalibration also happening to 2 adjacent machines any assistance would be much appreciated

ptsac
24-12-2008, 07:02 PM
Hi Dave,
Is the 170 Amp draw a measurement taken at the contactors. If this unit is star delta any single measurement on the six cables will need to be divided by 0.58 to give true motor current. 170 Amps would equate to 293 A.

GHAZ
24-12-2008, 10:01 PM
Hello Dave Hammo give us the compressor model and chiller model numbers and i,ll see if i got the full info on them to help, i assume it is slic frame two screw compressors.

dave hammo
25-12-2008, 12:19 AM
gday ghaz the current is taken from the display panel from a current transformer on incoming supply

dave hammo
25-12-2008, 12:26 AM
gday ghaz im heading up where the units r on mon after holidays 9middle of desert in central aust gas fields but from memory the model nos are 81.2 als ha(high ambient) frame 4 compressors with microtech 2 controllers

nike123
25-12-2008, 08:46 AM
gday ghaz the current is taken from the display panel from a current transformer on incoming supply
Check you current measurements with True RMS clamp ampermeter.
You must be sure in your data before taking actions upon them.

dave hammo
25-12-2008, 01:57 PM
thanks nike 123 these amps have been verified by clamp meter on all 3 units

psycho
11-01-2009, 08:53 AM
hello dave,
Its allways wise to take actual suction line temps to calculate superheat as the suction sensors are pretty useless,generally 6c split over the evap is bout all you can get anyway. Theres a manuall exv setting thats ussually 500 steps but its unlikely to be set for manual.At 500 steps open at 100 percent i'd expect the superheat to be way high ,and theres probably a high, discharge temp safety (s.p 110c in uk,not sure about hi ambiant models) that may not be breached if you got liquid injection.
definately compare displayed suction temps with actual.

dave hammo
11-01-2009, 11:03 AM
thanks 4 that psycho wwhen i went to site i found precoolers being incorperated at35c had those reset to come in to play when ambient temp hit 45c this increased amps drawn significantly however still have problem with holding chilled water temps on start up machines pull down but efficiently with evx valves opening and closing accordingly to maintain 5c superheat however during the day(normally ambients over 36c) the leaving chilled water wanders to 12c with slide valve position supposedly at 97% but evx once again at 400 steps out of 2600 and amp draw only 140a also having low press faults and low press ratio faults its got me bamboozeled evx valve still maintaining 5c superheat checked waterflows thru chillers all seems ok

GHAZ
11-01-2009, 11:17 AM
Hello Dave hav,nt worked on frame 4 but the older screws had a check valve in the suction cover and when stuck it caused low suction pressure .

dave hammo
11-01-2009, 11:22 AM
dont fret psycho i also sit back at home with my flip flops on knocking the froth off a cold one writing jibberish

psycho
11-01-2009, 11:29 AM
im not even sure that the machines you have are simmillar to here.those sub cooling heat echanger's have a software controlled s.p to operate the solenoid coil but i dont remember it being an adjustable parameter on the software that ive seen.you could probably explain to me how sub coolers affect head pressure and hence run amps!definately if you havent checked actuall pressure transducer and thermister readings with displayed its a good idea too,there is mbe a max pull down rate (c/min)that u could look at,wasnt sure iff you meant machines pull down efficiently or in- efficiently.
did you check water flow or p.d across evap?actually sounds a bit like low load on the evap.?

dave hammo
11-01-2009, 11:57 AM
gday psyco,these machines have aftermarket precoolers that is large evapcooler pads installed infront of air cooled condenser coils i take on board thr issue with the the suction temp probes giving false superhest readings all 6 comps of 3 chillers having same problem ito would think it was a system fault(water flow issues) however ive checked pd across evap vessel and they are well within design parameters the machines at inital start up perform well ie efficently but after several hours they cant hold chilled water temp(6c) but no fault present lp220 hp1050 all these readings ive mentioned are from display panel next time im heading up there i will manually take press temps etc the chillers are 4yrs old at least but only now getting commisioned fully does anybody know if there were eprom problems with chillers of this vintage