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Thread: Great problem........
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23-05-2010, 06:59 AM #1
Great problem........
We are using HITACHI chiller Model No.: RCUP-46AUZ,
To day when we run the system we find some abnormality, no cooling at all! chilled water inlet & outlet temp. is same. we measure subcool temp. its less then one & compare with previous discharge temp. it decrease nearly half (from 340PSI to 175PSI), then we try to measure suction pressure but we found lots of oil mixing with refrigerent like detergent shop bubble. We stop the chiller, what should be our steps now?
Note: Two days ago we change the chiller position and we run the unit today.
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23-05-2010, 11:39 AM #2
Re: Great problem........
hi,
water is short cycling.you hve to ope up the barrel and c the partiton gasket is broken.
thanks,
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23-05-2010, 11:50 AM #3
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24-05-2010, 07:42 AM #4
Re: Great problem........
Not enough readings to help you properly. If it's like soap: liquid refrigerant has entered you oil and this is foaming up when you start up. Crankcase heater switched on long enough?
Evacuate once you compressor body with a recuperation station and pump it to the receiver. Measure crankcase temperature while pumping out and see if it drops in temperature, then you know if there was liquid.
If you worked on the machine and problems started afterwards, you must find reason what went wrong when you worked on that machine.It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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25-05-2010, 07:01 AM #5
Re: Great problem........
Sir,
Our compressor model is semi-hermetic screw compressor 50ASCP-Z, I don’t think soap forming inside the line, its the compressor oil mixing with the refrigerant.
I am giving you all the data whatever i have:
Evap. Entering Water Pr. 48 PSIG
Evap. Leaving Water Pr. 30 PSIG
Ref. Discharge Pr. 1.20 MPa.
Ref. Suction Pr. 0.53 MPa.
Discharge Gas Temp. 43 deg. C
Suction Gas Temp. 11 deg. C
Water cooler inlet ref. gas temp. 8 deg C
Liquid ref. Temp. 320deg C
Chilled water inlet and outlet temp. 11 deg. C
Setting water temp. 7 deg. C
ON/OFF diff. 2 deg. C
Ambient temp. 30 deg. C
Note: All the data I found from the panel board and parallely there are another two chiller in that system.
Now I giving you the data I measured,
Suction pr. 80 PSI, Discharge pr. 175 PSI, Subcooling temp. 0.5 deg C.
Condenser inlet and outlet air temp. 30 and 31 deg. C
Compressor amp. 50.3, no fault showing in the panel what so ever!
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25-05-2010, 09:04 AM #6
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Re: Great problem........
Pressures don't mean anything without knowing refrigerant in unit.
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25-05-2010, 09:35 AM #7
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25-05-2010, 07:59 PM #8
Re: Great problem........
check water filter (blocked) ??
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26-05-2010, 03:19 AM #9
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26-05-2010, 03:55 AM #10
Re: Great problem........
Hi there,
With the figures you gave, it seems that you have liquid flood back.
At suction pressure R407C 's dew point is around 10°C and your suction gas temp. is 11°C. This means liquid flood back. When this happens then you get a lot of foaming in the crankcase.
Check if you have enough water flow.Even Einstein Asked Questions
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26-05-2010, 09:50 AM #11
Re: Great problem........
Today I observe:
Water cooler inlet ref. gas temp. 1.5 to 2.5 deg C
Comp. Suction temp. 5.2 Deg C
Why this temp. is so low? Still no cooling effect!
Measured Value:
Suction Pressure55PSISuction Temperature5.2CDischarge Pressure190PSIDischarge Temp33.5CPressure after TEV 88PSITemperature after TEV1.5 to 2.5CTempe. After compressor (Discharge line)58CTemp. of exhaust temp.39.3C
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01-06-2010, 08:16 AM #12
Re: Great problem........
Model Hitachi RCUP46AU(Z)
Date: 01.06.10
Parameters at 12:30 PM ,12:40 PM, 12:50 PM, 1:00 PM
Suction Pressure (Mpa): 0.55, 0.44, 0.41, 0.43
Discharge Pressure MPa: 1.72, 1.83, 1.84, 1.38
Discharge Temp Deg C: 73, 80, 79, 79
Liquid ref. temp. Deg C: 46, 48, 48, 49
Water cooler inlet Rfgt. Gas temp Deg C: 11, 8, 7, 6
Suction Temperature Deg C: 18,13,9,7
Chilled water inlet temp. Deg C:25,22,20,18
Chilled water outlet temp. Deg C: 24,21,19,17
Amp. taken by Chiller: 68 amp,67.8,67.5,68
Environmental temp. Deg C: 36,35,35,36
Note: Rated Chiller Amp. 76 & Refrigerent use R407C
Every time chiller is tripping arrived this condition with the fault of 13 13, it indicate that cmpressor is stop on freeze protection thermostat, we check all the temp. & presser sensor, solenoid valve of comp. thermistor, chilled water flow, air in water ckt. all are ok.
Any Help?Last edited by Bashir01219; 02-06-2010 at 03:38 AM.
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02-06-2010, 06:29 PM #13
Re: Great problem........
what type of evaporator is it? Plate heat exchanger or shell and tube?
It would appear that there is a lack of heat exchange occuring, if it is a shell and tube it is possible that the refrigerant is bypassing the evaporator via. a split end gasket, allowing low pressure liquid refrigerant through to the suction. I have had a similar problem in the past but my concern was with the low superheat. The compressor turned out to have the wrong oil, mineral instead of synthetic. This caused waxing on the evaporator tubes which reduced the heat exchange and superheat.
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03-06-2010, 08:21 AM #14
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Re: Great problem........
Last edited by nike123; 03-06-2010 at 11:03 AM.
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03-06-2010, 02:08 PM #15
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03-06-2010, 02:23 PM #16
Re: Great problem........
Yes Sir, You are right, but the previous position was so congested for the chiller that condenser air flow was terribly bad.
Now we charge the system, as supplier told us to do that, now Discharge pressure avg. is 1.84 MPa, Suction Pr. avg. is 0.38 MPa. Discharge gas temp. 65 C, Suction gas temp. 12 C, Water cooler inlet ref. gas temp. 5 C, Liquid ref. temp. 48 C, Chilled water in and out temp 17 & 16, ambient temp. 28 C. Not sufficient cooling is not it?
Sir, Second & third step of Result, I did not understand?
Actually we have three Hitachi chillers all are in parallel, others are running ok, so i thought water flow is ok! All water inlet pressure is same.
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03-06-2010, 04:11 PM #17
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Re: Great problem........
We need full readings. Your measurements are incomplete!
Evap air/water in temp
Evap air/water out temp
Low side pressure or saturation temp
Suction line temp at evap outlet!!!
Suction line temp at compressor inlet
Cond air/water in temp
Cond air/water out temp!!!
High side pressure or saturation temp
Liquid line temp at receiver or condenser outlet!!!
Liquid line temp at TXV inlet!!!
The more information provided the more accurate the diagnosis.
Check fan rotation direction.
You still don't have enough subcooling.
Without knowing condenser air on and off temperatures we cannot see what condenser is doing!
TD of evaporator is evaporator water in temperature minus R407 mean evaporation saturation temperature (because of temperature glide it is used mean evaporation temperature). For example:
Twi= 17°C
(R407C at 0,38Mpa has 1,5°C dew point and -5°C bubble point therefore mean evaporation temperature is -5°C +1/2 od 6,5°C glide = -1,75°C)
Te=-2°C
Twi-Te=17 - (-2)= 19K
Evaporator aproach is difference between evaporator water leaving temperature and evaporation saturation mean temperature.
A higher than normal evaporator approach can indicate an undercharge.
Similar is for condenser side.
Condenser TD is condenser mean saturation temperature minus condenser air in temperature
Condenser aproach is is condenser mean saturation temperature minus condenser air off temperature.
High condenser approach mean dirty condenser. High condenser delta t mean low air flow.
I made some mistakes in my table. Now it is corrected.
Your lack of any subcooling and high evaporator approach indicate that you are still short of refrigerant.
recover and charge by weight, then take a new full set of readings as listed above.
I asked what is this:
Water cooler inlet Rfgt. Gas temp Deg C
You did not answered.
If it is what is written than that reading is useless.
We cannot conclude anything from reading temperature of pipe between TXV and evaporator.
What we need is temperature and pressure of pipe 10-15 cm before expansion valve. That tell us if we have subcooled liquid before TXV.
Your evaporator water flow should be measured with flow meter. Pressure at inlet doesn't mean anything.Last edited by nike123; 03-06-2010 at 06:31 PM.
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04-06-2010, 05:36 AM #18
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04-06-2010, 06:04 AM #19
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Re: Great problem........
At the enter of HE is liquid gas mixture after TXV and that temperature is of no use (it is not saturated temperature) because gas is not there because of evaporation but because of pressure drop at TXV.
We need liquid line temperature 15 cm before expansion valve (to see if there is pure liquid refrigerant at TXV inlet) and we need pipe temperature after HE where TXV bulb is placed (to find evaporator superheat and proper TXV operation).
Take your measurement with accurate calibrated service instrument and not with unit sensors. You could give unit sensor readings only when you check wit accurate service instrument that their readings are accurate.
Take your reading only when capacity control is at 100%Last edited by nike123; 04-06-2010 at 06:22 AM.
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07-06-2010, 08:52 AM #20
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07-06-2010, 08:59 PM #21
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Re: Great problem........
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09-06-2010, 03:16 AM #22
Re: Great problem........
Sir,
Following data I measured, we check all the pr. & temp. sensor so you can trust on my data.
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09-06-2010, 07:47 AM #23
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Re: Great problem........
What did you done on chiller between last posted measurements and this measurements? Your discharge pressure and amperage is significantly dropped with same ambient temperatures since last measurement.
Do not "throw" data at us without explaining what is done between measurements. Remember, we are not there.
I see now that condenser is doing OK! That mean that evaporator is picking some heat. It looks like evaporator having some serious overflow!
Edit: I made some mistakes in calculation for above sentence. It does not look OK and it does not picking much heat.
Did you measured water flow?
Your results are not good. Formulas are wrong. Upload your excel file in order to see what is wrong with formulas.Last edited by nike123; 10-06-2010 at 06:51 AM.
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09-06-2010, 08:35 AM #24
Re: Great problem........
hi basheer,what is comp.RLA AND current running ampere.you are sure compressor is full load.this is screw,so it may work under 10% capacity.have you check the loading unloading.waiting your replay.
Moideen-dubai
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09-06-2010, 09:02 AM #25
Re: Great problem........
Dear Sir,
After that measurement we recharge the chiller and after that we observe compressor is taking more then 100 amp (but its actually 76 amp rated), we discharge some refrigerant and its still taking more then 90 amp, then we need to close for that day (office time closed). And again next morning we measured the value and find the attached file data.
In-between this we checked all the sensors, valve and chilled water flow rate of evaporator (approximately 30 m3/hr).
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09-06-2010, 09:05 AM #26
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09-06-2010, 10:49 AM #27
Re: Great problem........
Your txv orifice is fixed or replaceable? Your evaporator approach temp. Is very high. this clear evidence that there is not take place heat transfer. I think your evaporator is fouled. check your evaporator individually.
Moideen-Dubai
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09-06-2010, 11:16 AM #28
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09-06-2010, 11:51 PM #29
Re: Great problem........
Are u sure u have flow through the evap? Flow and pressure not the sane thing.
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10-06-2010, 02:58 AM #30
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10-06-2010, 06:24 AM #31
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Re: Great problem........
Check that you have correct water flow direction. It must be counter flow with refrigerant.
Chiller.zip
Last edited by nike123; 10-06-2010 at 07:17 AM.
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10-06-2010, 07:04 AM #32
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10-06-2010, 07:17 AM #33
Re: Great problem........
Sir, If possible correct my formulas in the attached file, and how can I use it for fault finding?
Its difficult for me, because of my little knowledge, I have all the charts, tables collecting from this forum but some data is not matching with your given table and most of the data I am not finding from the chart, in one wards it’s not clear to me (result column of your chart).
I understand you are too busy and sometimes you may angry with my questions!
I will love to thanks you again……..
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10-06-2010, 07:19 AM #34
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10-06-2010, 07:24 AM #35
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Re: Great problem........
I made correct table and attached in my previous post.
Read carefully what I described how to get results in my previous posts in this thread and check formulas in that excel file result fields. Than ask what is not clear to you.
Check this page:
http://www.air-conditioning-and-refr...er-system.htmlLast edited by nike123; 10-06-2010 at 08:36 AM.
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10-06-2010, 07:31 AM #36
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10-06-2010, 07:58 AM #37
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Re: Great problem........
Here it is not clear what you done. If you removed refrigerant and measured 90A than closed for that day, how than that next measurements of current are with low amperage from 45 to 60 A and not 90A as you measured day before, without fiddling with refrigerant charge again or with unloading and loading of compressor. Since that chiller is with continuous capacity control, how did you force it to stay at full loading?
If you done something in between 9 and 12 hr when these measurements in excel table are taken, than you should say what is done in what time.Last edited by nike123; 10-06-2010 at 08:10 AM.
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10-06-2010, 08:02 AM #38
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Re: Great problem........
With that method you are not taking in account all restrictions in system since you changed water path to measure flow. Therefore, measured flow doesn't represent actual flow. You need ultrasonic flow meter or pressure differential meter on flow measuring valve with known kv.
Is that flow constant or you having regulating devices which my change flow?Last edited by nike123; 10-06-2010 at 08:08 AM.
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10-06-2010, 08:27 AM #39
Re: Great problem........
Can the OP stop the chiller & open the evaporator? Take some pictures of the evap & let us have a look.
Your evap is clearly not picking up heat, for some reason. I've seen comments regarding either water, or refrigerant bypassing - or, incorrect pipework.
Do you have an idea of what the correct refrigerant charge is for your system? If so, what is your present charge?Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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10-06-2010, 08:45 AM #40
Re: Great problem........
When we measured 90Amp. then we only ran one chiller for total system, its a closed loop and nearly 3000 ltr water in the ckt, and again in the next morning when we measured the data another chiller of 90 ton was running with the system, may be its a cause or we have a leakage in the system that causes leaking of refrigerant which causes low amp. of the compressor in the next morning.
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10-06-2010, 09:03 AM #41
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10-06-2010, 09:18 AM #42
Re: Great problem........
The system was charged 3 and half years ago when I was in another plant. From previous commissioning data temp. Difference through HE always 1-2 C.
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10-06-2010, 09:26 AM #43
Re: Great problem........
Amperage measured at compressor power connections.
& compressor did not trip for high amp. even its amp. reached 103 amp.
One of our engineer checked and replay us it will trip after a certain period of time. Only the chiller tripped for freezing fault for several times. Whenever HE inlet ref. temp. reached at 3 deg. C.
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10-06-2010, 10:53 AM #44
Re: Great problem........
This caught my eye.
The thought occurred to me that if the water were to have frozen & deformed the inside of the PHE - without rupturing the plates - that perhaps the water is simply bypassing the rest of the evap?
What are the real refrigerant-side pressure drops like in the evap, I wonder? I'll go back through your measurements again, before I comment further.Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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10-06-2010, 02:08 PM #45
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10-06-2010, 03:09 PM #46
Re: Great problem........
@Bashir,
I'm looking to see what you have mentioned about your air-cooled condenser. To me, the air is heating up a lot, considering that the evap is hardly operating.
What is happening to the condenser fan? What is the air velocity entering the condenser face? I'd expect it to be in the range ~ 1.8 - 3.6 m/s. What have you got?Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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10-06-2010, 04:51 PM #47
Re: Great problem........
Are there any head-pressure control valves, or hot-gas bypass circuits in this system?
I have to also wonder if someone has not perhaps worked on the system & topped up with the incorrect gas, or oil? Something weird seems to be going on.
Perhaps it would be an idea to reclaim the refrigerant, drain the oil, flush the system, replace filter-drier/s, clean/check TXV orifice, add new oil charge, pressure test with N2, purge with N2/vacuum x3, add fresh refrigerant to manufacturer's recommendations? I'm concerned that something may has occurred in the system that is not obvious from the data we are seeing. At least then you will have a firm base to work from.Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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11-06-2010, 05:32 AM #48
Re: Great problem........
No Head-pressure control valves or hot-gas bypass circuits in this system, or filter-drier(all inside the compressor).
Ok, I am clearing you, its a three and half years old system, as per our maintenance history book we never topped up the system only we clean the evaporator for six time (in last one year), and clean the condenser fin as outside environment is quite dirty.
And recently we changed the chiller position and find not sufficient or no cooling, and then we charge/topped up the system (we charge slowly as by weight & also monitor comp. amp).
One thing is common that previously chiller was tripped due to frizzing fault and still that problem present, we check all the thermocouples (chilled water in/out, freeze protection), find no problem.
We are already asked for spare parts to the supplier, but if the problem present inside HE then what happen if we change EEV, charge the system properly, still system will act as present. I think management will not forgot or forgive us!
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11-06-2010, 03:14 PM #49
Re: Great problem........
I agree recover charge and oil and start fresh. Any way to measure pressure drop accross evap? Check agains design op.
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12-06-2010, 03:12 AM #50
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