Great problem........

[Bashir01219]

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.

[bmundoorkote]

hi,
water is short cycling.you hve to ope up the barrel and c the partiton gasket is broken.
thanks,

[Bashir01219]

hi,
water is short cycling.you hve to ope up the barrel and c the partiton gasket is broken.
thanks,
no water in the line, its oil!

[Peter_1]

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.

[Bashir01219]

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.
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!

[nike123]

Pressures don't mean anything without knowing refrigerant in unit.

[Bashir01219]

Pressures don't mean anything without knowing refrigerant in unit.
Sorry, I just miss.....
Its R407C

[frederik79]

check water filter (blocked) ??

[Bashir01219]

check water filter (blocked) ??
We checked it at first......

[lana]

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.

[Bashir01219]

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.
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 Temperature5.2C Discharge Pressure190PSIDischarge Temp33.5C Pressure after TEV 88PSITemperature after TEV1.5 to 2.5C Tempe. After compressor (Discharge line)58CTemp. of exhaust temp.39.3C

[Bashir01219]

Pressures don't mean anything without knowing refrigerant in unit.
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?

[mgtet]

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.

[nike123]

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?

What is this marked with red?
Is this relocated chiller which run fine before relocation?
How did you checked water flow? Did you actually measured flow? How much is it?

From numbers, you have no subcooling at all. It look like you are short of gas!


http://i45.tinypic.com/wgqixz.jpg

[Bashir01219]

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.
No its a plate type heat exchanger.

[Bashir01219]

What is this marked with red?
Is this relocated chiller which run fine before relocation?
How did you checked water flow? Did you actually measured flow? How much is it?

From numbers, you have no subcooling at all. It look like you are short of gas!


http://i45.tinypic.com/wgqixz.jpg
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.

[nike123]

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.

http://i49.tinypic.com/17v4hw.jpg

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.

[Bashir01219]

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.

http://i49.tinypic.com/17v4hw.jpg

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.
Sir, I am out of plant for two days training program. I will gave you all the data on 06/06/2o1o.
Water cooler inlet temp. ? its the liquid ref. temp enter into the HE.

[nike123]

Sir, I am out of plant for two days training program. I will gave you all the data on 06/06/2o1o.
Water cooler inlet temp. ? its the liquid ref. temp enter into the HE.

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%

[Bashir01219]

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%.

Sir,
How can I attach a Excel paper? or give me your mail ID that I can mail you!

[nike123]

http://www.refrigeration-engineer.com/forums/faq.php?faq=vb3_reading_posting#faq_vb3_attachments

[Bashir01219]

Sir,
Following data I measured, we check all the pr. & temp. sensor so you can trust on my data.

[nike123]

Sir,
Following data I measured, we check all the pr. & temp. sensor so you can trust on my data.


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.

[moideen]

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:)

[Bashir01219]

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).

[Bashir01219]

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:)
Yes, we check loading/unloading of compressor.

[moideen]

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.:confused:
Moideen-Dubai

[Bashir01219]

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.:confused:
Moideen-Dubai
Its an Electronic Expansion Valve with modulating control.
If the problem with HE then we are in big trouble because just few days ago we clean the water line.

[ktm]

Are u sure u have flow through the evap? Flow and pressure not the sane thing.

[Bashir01219]

Are u sure u have flow through the evap? Flow and pressure not the sane thing.
Yes, we measured the flowrate before and after HE.

[nike123]

Check that you have correct water flow direction. It must be counter flow with refrigerant.

3554

http://i46.tinypic.com/2cmt201.jpg

[Bashir01219]

Check that you have correct water flow direction. It must be counter flow with refrigerant.
But Sir, it’s installed correctly as we installed othr chiller and as per manual.

[Bashir01219]

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).
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……..

[nike123]

But Sir, it’s installed correctly as we installed othr chiller and as per manual.
Describe how did you measured water flow?!

[nike123]

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……..


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.

http://i46.tinypic.com/rmp4yf.jpg
[/URL]

Check this page:
[URL]http://www.air-conditioning-and-refrigeration-guide.com/water-chiller-system.html (http://www.refrigeration-engineer.com/forums/showpost.php?p=92775&postcount=5)

[Bashir01219]

Describe how did you measured water flow?!
Oh! Sorry when I am writing my next question you already answer it.

For measuring the flow rate we use raw method, Q= volume/time, as we have no flow meter for this purpose.

Take a drum with known volume and we take time to fill it.

[nike123]

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).


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.

[nike123]

Oh! Sorry when I am writing my next question you already answer it.

For measuring the flow rate we use raw method, Q= volume/time, as we have no flow meter for this purpose.

Take a drum with known volume and we take time to fill it.


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?

[desA]

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?

[Bashir01219]

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.
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.

[nike123]

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.

So question is where did you measured amperage, since 100A or 90A will trip compressor safety devices?
Amperage should be checked at compressor power conections.

[Bashir01219]

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.

[Bashir01219]

So question is where did you measured amperage, since 100A or 90A will trip compressor safety devices?
Amperage should be checked at compressor power conections.
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.

[desA]

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.

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.

[Bashir01219]

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.
Thanks Sir, I am waiting for ur replay.

[desA]

@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?

[desA]

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.

[Bashir01219]

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.
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!

[ktm]

I agree recover charge and oil and start fresh. Any way to measure pressure drop accross evap? Check agains design op.

[Bashir01219]

I agree recover charge and oil and start fresh. Any way to measure pressure drop accross evap? Check agains design op.
Sometime I can no believe my luck! Wherever I go, whatever I see, I always found problems………..
Pressure drop across Evaporator 1.2 bar,
Read properly before answer.

[nike123]

Whenever HE inlet ref. temp. reached at 3 deg. C.

If your HE has Δt of 0K or 1K as measured and stated in your data than freezing fault mean that your set point is set to low or you have some changes in water flow during operation that can lead to high Δt. Or you have faulty temperature sensors.

Also, alarm of 3°C should be triggered by water outlet temperature.

According to our previous discussion (http://www.refrigeration-engineer.com/forums/showthread.php?t=24961) I think that main problem there is incorrect water flow which probably varies as other circuits on that network closes or opens for regulation and by that action changes balance of flows. That can be connected with reading of evaporation temperature at 9:10, 10:30, 11:30. So you should first ensure steady and corect water flow at that chiller. Where did you measuring water outlet temperature. Is that measured at common pipe of other chillers, or at evaporator outlet?

Next what can be read from your data is that you still have lack of any subcooling. Ether it is short of refrigerant, incorrect or contaminated refrigerant or your air flow is incorrect or your heat exchanger need cleaning.
So you should measure airflow, clean condenser and recover portion of refrigerant in drum and check its correct PT ratio.

Also, according to your data, you have negative approach at condenser in amount which is possible only when there is no saturated refrigerant there.
If there is no liquid refrigerant at enter of EEV than there is no liquid refrigerant that evaporate and that is why other data looks like that in your table.

No subcooling at condenser outlet
No subcooling at EEV inlet
Low amperage
High evaporator approach
Negative condenser approach (no saturation)

[moideen]

everybody confirm that PHE is in trouble.so better to overhaul or replace PHE.please go to this link.you can down load PHE maintenance manual
http://www.schaufcompany.com/v3/owner/alfalaval.html:)moideen-dubai

[Bashir01219]

Sir,
Thanks, we will do what you suggest.
We measured chilled water temperature just after the HE, actually we provide two temperature gauges in the chilled water inlet & outlet, and we calibrate it several times with the testo apparatus. And we can check it through inlet outlet sensors.

[Bashir01219]

Thanks Sir,
@moideen
It will help us lot.

Thanking You,
Bashir

[eghbali]

It explained that the density of subcooling on refrigeration for correctly making the expansion valve is necessary saturation temperature of 15 degrees Fahrenheit above the temperature cycle is good.
Better characteristics for proper charging system is suctionsuperheat saturation temperature above 10 degrees Fahrenheit is good.If this rate is higher undercharge system. If this amount was less overcharge system</SPAN>

[nike123]

It explained that the density of subcooling on refrigeration for correctly making the expansion valve is necessary saturation temperature of 15 degrees Fahrenheit above the temperature cycle is good.
Better characteristics for proper charging system is suctionsuperheat saturation temperature above 10 degrees Fahrenheit is good.If this rate is higher undercharge system. If this amount was less overcharge system</SPAN>

To use superheat or subcooling as indication of charge depend on used metering device. Since here is EEV which maintin programed superheat, correct is charging by subcooling.

[Bachuss]

Have you checked that the evaporator is clean and clear on the water wide, in many places even supposedly clean water can leave scale which creates a restriction in the water lines and insulation from the refrigerant both of which will stop your water from chilling.

[Bachuss]

To use superheat or subcooling as indication of charge depend on used metering device. Since here is EEV which maintin programed superheat, correct is charging by subcooling.

Personally I don't think you can use only sub cooling or super heat to charge a system, you should also be watching the motor running amps of the compressor and your sight glass.

[Bachuss]

Sometime I can no believe my luck! Wherever I go, whatever I see, I always found problems………..
Pressure drop across Evaporator 1.2 bar,
Read properly before answer.


No offence intended but is hard to read properly when English is so obviously not your first language. :rolleyes:

[Bashir01219]

No offence intended but is hard to read properly when English is so obviously not your first language. :rolleyes:
What does it mean?
Maybe I just miss a "T", no=not; when you are busy this might happen.

[Bashir01219]

Have you checked that the evaporator is clean and clear on the water wide, in many places even supposedly clean water can leave scale which creates a restriction in the water lines and insulation from the refrigerant both of which will stop your water from chilling.
Yes, we clean as described by the HE supplier, SWEP.

[Bashir01219]

To use superheat or subcooling as indication of charge depend on used metering device. Since here is EEV which maintin programed superheat, correct is charging by subcooling.
Sir,
After cleaning the HE, and adjusting the chilled water inlet and outlet flow we are getting improved result (I mentioned improve result only the basis of chilled water inlet and outlet temp. diff. previously it was 1 or 0 but now it consistently 2 or 3). We close 70% chilled water inlet line & 10% chilled water outlet line (valves r butterfly). What is the logic? If i want to set up a logic. We yet not charged the system as refrigerant is not available, it will take some time.

[nike123]

Sir,
After cleaning the HE, and adjusting the chilled water inlet and outlet flow we are getting improved result (I mentioned improve result only the basis of chilled water inlet and outlet temp. diff. previously it was 1 or 0 but now it consistently 2 or 3). We close 70% chilled water inlet line & 10% chilled water outlet line (valves r butterfly). What is the logic? If i want to set up a logic. We yet not charged the system as refrigerant is not available, it will take some time.

OK good! You need now to take whole set of measurements again. Try to provide all data as asked before. It is essential to cover all data for proper evaluation.

[nike123]

Personally I don't think you can use only sub cooling or super heat to charge a system, you should also be watching the motor running amps of the compressor and your sight glass.

Motor running amperes are dependent on mechanical state of compressor and compression ratio. With corect charge and various temperatures of evaporation and condensation (which depends on many things) you have various current reading. Therefore, current of compressor is not clear indication of correct charge, but it should be monitored in case if something other is wrong, or to be sure that you are not grossly overcharged.
Sight glass could be misleading especially with blends because they represent difference in flow resistance (therefore pressure change) and liquid refrigerant could flash in sight glass and collapse again after sight glass when flow restriction become same as before sight glass.

Proper subcooling and proper superheat along with proper air/water flows and cleanliness of heat exchangers will tell you that you have balanced and properly charged system.

[icecube51]

how has this story ended??? ore is the problem still on??

Ice

[garethjones10]

Hello

This is Gareth Jones

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.

Gareth
CNM ONLINE

[Bashir01219]

sometnhing may happen with the page, I can not replay

[Bashir01219]

@ICE: This is really frustrating for all of us, our knowledge is limited but we tried all the possible ways. It seems that the problem with the beginning or commissioning period nearly two & half years ago (and that time I worked in another Cement plant), we did not have the commissioning report, and if we analysis last one and half year’s operation log sheet we found some interesting observation:

[Bashir01219]

We open the LC for some spare parts and offer help from local HITACHI supplier, hoping that they will fill & understand what they have done with the system two years ago!

[moideen]

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%

hi nike,trane RTAA,chilers have installed suction saturation thermistor after exv ,before reaching HE.
could you clear me
moideen

[nike123]

hi nike,trane RTAA,chilers have installed suction saturation thermistor after exv ,before reaching HE.
could you clear me
moideen

Maybe I am wrong in my thinking that flash gas and liquid refrigerant mixture at exit of EXV is not in saturated state. Maybe someone could clear that for both of us.

Here is some thread with that thematic:
http://www.refrigeration-engineer.com/forums/showthread.php?t=888

[moideen]

We open the LC for some spare parts and offer help from local HITACHI supplier, hoping that they will fill & understand what they have done with the system two years ago!
hi bashir,why u r silent?what is the status your chiler?problem solved..............;)
moideen

[Bashir01219]

hi bashir,why u r silent?what is the status your chiler?problem solved..............;)
moideen
No, we are waiting for the spare and HITACHI local suppliers, they need some time.

[nike123]

Spare evaporator perhaps?

[icecube51]

spare complete unit (LOL)

Ice

[Bashir01219]

spare complete unit (LOL)

Ice
Hummmmmmmmmm........
Lets see what they (HITACHi) do!

[nike123]

I am sure that are so many China made chillers of better quality than Hitachi.:rolleyes:

[dgt]

check if you dont mixed two kind of oil

[Bashir01219]

I am sure that are so many China made chillers of better quality than Hitachi.:rolleyes:
Sir,

They provide us lots of papers and ask for data, now we are waiting, waiting, & waiting..............

@dgt: We did nothing with the compressor ever

[lma]

Hi..

I am new to the site and this is my first post. Not sure what the update is at present ... the post being close to two months now.

I have followed with interest your discussion above and I am curious to know the outcome ... and what made you believe there was a problem in the first place. You mentioned no cooling ... what was the temperature of the medium being cooled ?

What made you believe there was a problem with the chiller ?

Regards

[Bashir01219]

Thanks for your curious....
At present the unit is under servicing of Hitachi personeel, they are not only slow but also boring.
The main problem is with the evaporator, pressure difference too high........any way lets see what r they doing?

[Bachuss]

Motor running amperes are dependent on mechanical state of compressor and compression ratio. With corect charge and various temperatures of evaporation and condensation (which depends on many things) you have various current reading. Therefore, current of compressor is not clear indication of correct charge, but it should be monitored in case if something other is wrong, or to be sure that you are not grossly overcharged.
Sight glass could be misleading especially with blends because they represent difference in flow resistance (therefore pressure change) and liquid refrigerant could flash in sight glass and collapse again after sight glass when flow restriction become same as before sight glass.

Proper subcooling and proper superheat along with proper air/water flows and cleanliness of heat exchangers will tell you that you have balanced and properly charged system.

Thank you nike, as usual your posts are very informative and help me greatly in my learning.

[Bashir01219]

Dear Sir,
How r U?
After long time and collecting data they decide to clean the HE and install a flow control valve in chilled water inlet line. Now the pressure diff. between chilled water in and out is 0.5 bar which is recommended by HITACHI.
I am also attaching a data sheet with this mail (after their work).
Note: Still suppliers are working.
If possible analyze the data sheet and give your suggestion.

[nike123]

From quick look I see your evaporator dT is still small (1-2K).
Did you, or did you not confirmed correct flow of water at all times. It should be around 0,15-0,20 m^3/h per kW of chiller capacity.
Also I see high dT on condenser which mean low air circulation at condenser. Are you sure that fan is spinning in correct direction (suction from outside across fins and than at fan blades then exhaust at outside)

[Bashir01219]

Also I see high dT on condenser which mean low air circulation at condenser. Are you sure that fan is spinning in correct direction (suction from outside across fins and than at fan blades then exhaust at outside)[/QUOTE

Yes Sir your idea is correct, previously chiller unit installed in ground floor and beside the unit there was a garments, that's why condenser fines are blogged with cotton type dust, its acting like glass wool insulator inside the condenser fines. we tried to clean the fines with pressurized water and soap water but it didn't work. The cotton dust are also not visible to us or we can not open the side cover of the condenser (plate & condenser pipe lapping each other, if we want to open side cover we need to cut the condenser pipe, which is difficult and risky).

Any suggestion?

[nike123]

Only what comes to my mind is to change condenser.

[Bashir01219]

Thanks, Its the best way to overcome the problems........