High Discharge Temperature!!! Very Critical

[MayankBhatia]

Hey friends

I am on a site where we have J&E hall Screw Compressor we do some Retrofit with chiller,And add only 40kg Gas R22(But Labeled 70Kg) and started MAchine. But Machine going in very high discharge Temperature.Which is not good for compressor Life.Below are the parameters for the same.Please Suggest What is wrong.Its a 4 circuit Chiller.


For refrence I am attaching Log in form of Image.

[Brian_UK]

What type of condenser do you have fitted?

Was a good vacuum achieved before regassing?

[Tesla]

What are your water in/out temps? Is this just after initial pull down of load. Just wondering if there was too much load on pull down, not that I know much about screws. Please include ambient temp and humidity too.

[MayankBhatia]

Condenser is Air Cooled.and yes we achieved 400 Micron in all circuts.

OAT: 42 °C Set Point:5.5 °C EWT: 11.6°C LWT: 6.1°C

[Magoo]

High oil temps and or low flow rates will effect discharge temps.

[moideen]

What is the chiller model No. and you said only charged 40 kg from total charged 70 kg gas. Then you have got the temperature entering and leaving is 11 and 6!! .be sure it is correct, and your suction super heat is not much high. Considering the all readings your gas charging is full and sufficient. What are the full load compressor amps to compare RLA. Restricted oil flow to the compressor will cause high discharge temperature. Check for main injection valve, oil orifice or filter blockage. Has your compressor oil cooling system?

[HVACRsaurus]

Looking at the condensing pressures & outside air temperatures - those discharge temperatures are probably to be expected..

[passandscore]

I am thinking the same thing! You can make improvements but I would except higher than normal discharge temperatures. What is your cutout point? 120c?

[MayankBhatia]

High oil temps and or low flow rates will effect discharge temps.

High Oil temperature?But what making oil Temp High.?At the start of Compressor at full load it shows 29 DSH but slowly slowly Discharge temp Increases.

And Can you little explain How flow Rate Will Effect?

[MayankBhatia]

What is the chiller model No. and you said only charged 40 kg from total charged 70 kg gas. Then you have got the temperature entering and leaving is 11 and 6!! .be sure it is correct, and your suction super heat is not much high. Considering the all readings your gas charging is full and sufficient. What are the full load compressor amps to compare RLA. Restricted oil flow to the compressor will cause high discharge temperature. Check for main injection valve, oil orifice or filter blockage. Has your compressor oil cooling system?

Its a Mcquay ALS Chiller.FLA was 160 Amps.

[MayankBhatia]

I am thinking the same thing! You can make improvements but I would except higher than normal discharge temperatures. What is your cutout point? 120c?

Cut point for Discharge temperature is 110 degree Celcius.

[Josip]

Hi, MayankBhatia :)


Hey friends

I am on a site where we have J&E hall Screw Compressor we do some Retrofit with chiller,And add only 40kg Gas R22(But Labeled 70Kg) and started MAchine. But Machine going in very high discharge Temperature.Which is not good for compressor Life.Below are the parameters for the same.Please Suggest What is wrong.Its a 4 circuit Chiller.


For refrence I am attaching Log in form of Image.

I have to admit have no experience with J&E Hall screws, but ... compressor like compressor or almost the same ...

discharge temp in single stage screw compressor for ammonia can go up to 105*C but with R 22 only up to 90*C ... maybe with air cooled condensers those value are higher ... anyhow problem is within oil temperature for bearings ... must not be over 75*C ...

seems your discharge temp is very high ... what is cause ....

suction superheat is quite low (what is good) ....

discharge superheat is very high, too high .. above 25K ... you have 36,3 to 39,5 K

oil pressure difference is OK from 0,7 to 1,0 bar ... permissible oil drop pressure can be max about 1,75 bar (0,35 bar g for clean filter + 1,4 bar)

seems your liquid refrigerant injection for oil cooling is not enough (I assume you start up your plant sometime in the winter period thus you did not have the same OAT like now ...maybe I'm wrong) thus you need to install small external oil cooler for additional oil cooling... no other way, sorry ...

with refrigerant injection for oil cooling discharge temperature above 75*C is not possible to maintain .... in your case discharge temperature are from 99,8 to 104,9*C (oil has the same temperature)

Hope this will be of some help to you.

Best regards, Josip :)

[MayankBhatia]

Hi, MayankBhatia :)



I have to admit have no experience with J&E Hall screws, but ... compressor like compressor or almost the same ...

discharge temp in single stage screw compressor for ammonia can go up to 105*C but with R 22 only up to 90*C ... maybe with air cooled condensers those value are higher ... anyhow problem is within oil temperature for bearings ... must not be over 75*C ...

seems your discharge temp is very high ... what is cause ....

suction superheat is quite low (what is good) ....

discharge superheat is very high, too high .. above 25K ... you have 36,3 to 39,5 K

oil pressure difference is OK from 0,7 to 1,0 bar ... permissible oil drop pressure can be max about 1,75 bar (0,35 bar g for clean filter + 1,4 bar)

seems your liquid refrigerant injection for oil cooling is not enough (I assume you start up your plant sometime in the winter period thus you did not have the same OAT like now ...maybe I'm wrong) thus you need to install small external oil cooler for additional oil cooling... no other way, sorry ...

with refrigerant injection for oil cooling discharge temperature above 75*C is not possible to maintain .... in your case discharge temperature are from 99,8 to 104,9*C (oil has the same temperature)

Hope this will be of some help to you.

Best regards, Josip :)

Do you mean i need to Increase orifice of Liquid injection?

[Josip]

Hi, MayankBhatia :)


Do you mean i need to Increase orifice of Liquid injection?


Actually no ... it is not allowed to you to alternate injection ports ... not your job ... it is installed by manufacturer to protect compressor ...

but, you can try, there is a big danger to have too much refrigerant within oil i.e. lack of lubrication what is not good either ...

... anyhow you can try to increase amount of injected refrigerant for oil cooling, but ... do it carefully and check oil pressure and discharge temperature ... and if need install additional external oil cooler ...

Did you check you liquid refrigerant line ... to injection port ... no lack of refrigerant in that line-pipe ...

Best regards, Josip :)

[RANGER1]

MayankBhatia,
What type of oil cooling do you have, as I can't find it in any of your above posts!

I have seen in one case with liquid injection that refrigerant injection tubes entering slide valves were worn & nearly all liquid leaked into suction & star wheel chamber. Maybe this is not relevant but worth mentioning.

Also how old are these compressors & have they performed with lower discharge temps in the past.

Discharge pressures seem excessive in all systems even for ambient of 42 C
From what I can find max dt 100C normal comp & 120C special max oil temp 80C
Max dp 27bar with it being on border of using liquid injection cooling.

[MayankBhatia]

MayankBhatia,
What type of oil cooling do you have, as I can't find it in any of your above posts!

I have seen in one case with liquid injection that refrigerant injection tubes entering slide valves were worn & nearly all liquid leaked into suction & star wheel chamber. Maybe this is not relevant but worth mentioning.

Also how old are these compressors & have they performed with lower discharge temps in the past.

Discharge pressures seem excessive in all systems even for ambient of 42 C
From what I can find max dt 100C normal comp & 120C special max oil temp 80C
Max dp 27bar with it being on border of using liquid injection cooling.

Compressors are Just brand New,as I told We retrofitted it.Oil is refregerant cooled.Its J&E Hall HSS Series3100 Compressor.

[moideen]

Compressors are Just brand New,as I told We retrofitted it.Oil is refregerant cooled.Its J&E Hall HSS Series3100 Compressor.
hi mayan

again let me confirm,you replaced only compressor.may i know before which compressor was used.is it same Mcquay?and give me chiller full model no.

regards
moideen-dubai

[MayankBhatia]

Yes it was Same Mcquay Screw Compressor, ALS294A.Please help?Could it be related to Flow anyhow?

[moideen]

Yes mayan, for screw compressors oil has multipurpose. Such
as lubrication, sealing of gas leakage and reducing the discharge temperature. And also your chiller has equipped with liquid injection. So you have to check two main things. Check the oil temperature, any restriction in oil flow and the liquid injection is working properly.

[MayankBhatia]

Yes mayan, for screw compressors oil has multipurpose. Such
as lubrication, sealing of gas leakage and reducing the discharge temperature. And also your chiller has equipped with liquid injection. So you have to check two main things. Check the oil temperature, any restriction in oil flow and the liquid injection is working properly.

The oil Temp is same as Discharge Temp.And Liquid Injection is working Fine.

And With flow mean Water Flow,As i am having only 3 PSi Pressure Drop across Evaporator.

[RANGER1]

Oil & discharge temp should be 90deg C so either liquid injection is not quite working 100% lack of refrigerant or needs adjustment

http://www.jehall.com/library/docs/hss-3200-app-iss-2.3-07-11.pdf

You may have information like this with new machines?

[MayankBhatia]

Oil & discharge temp should be 90deg C so either liquid injection is not quite working 100% lack of refrigerant or needs adjustment

http://www.jehall.com/library/docs/hss-3200-app-iss-2.3-07-11.pdf

You may have information like this with new machines?
Yes i am aware of that.I have set Liquid Injection solenoid coil to energize at 80 degree .And System doesnt show any sign of lack of refrigerant like Sub cooling is fine and Sight glass also clear.

[RusBuka]

Too high a pressure of condensation. Motor winding give much more heat, well it turns out DSH above norms.
For r-22 30-35 K OK

[nike123]

As RusBuka mentioned, too high condensation temperature (for that ambient temperature) is on these records. Compressors are overloaded. High discharge temperature is result of that overload. Condenser split (TD) is 21,5K to 23K (according to records) which is excessive to me. I would expect, in that climate, to use high efficiency condensers with split of 10K, no more! What if ambient temperature go higher?

So I will be first checking if condenser is clean, fans are rotating in right direction and at proper rpm-s. If you have condensation control, than I would try to run fans at full speed with bypassing condensation control circuit. If you have condenser air-flow design data, then it is best to measure actual condenser air flow.
I would expect there to have condensers with at least 300m3/h air flow per 1kW of chiller cooling capacity.
I am not pulling these numbers from my head. They are numbers from technical data of McQuay chillers ALS “E” XE ST (HFC 134a)

http://www.mcquay.ru/downloads/ALS%20E_tm_en.pdf

XE in designation means that it is high efficiency heat exchanger (condenser) which is able to run up to 48°C ambient temperature, which should be used in your area.


Also, these data will let you know if it is problem with design (to small condenser) or with function of condenser.
To me, in this case, condenser is starting point.

Also, I would measure condenser air exit temperature to be able to calculate condenser approach!

When you lower that split to 10K-12K, I expect you will have no more problems with high DSH, if everything else is OK.

[desA]

How certain is the OP that the refrigerant provided is in fact R22?

Certain Chinese blends - marked as R22 - can create all kinds of havoc in a system. I've seen this with refrigerant marked R134a, for instance. The difference in performance figures between DuPont R134a & Chinese 'R134a' is shocking!

[moideen]

As RusBuka mentioned, too high condensation temperature (for that ambient temperature) is on these records. Compressors are overloaded. High discharge temperature is result of that overload. Condenser split (TD) is 21,5K to 23K (according to records) which is excessive to me. I would expect, in that climate, to use high efficiency condensers with split of 10K, no more! What if ambient temperature go higher?

So I will be first checking if condenser is clean, fans are rotating in right direction and at proper rpm-s. If you have condensation control, than I would try to run fans at full speed with bypassing condensation control circuit. If you have condenser air-flow design data, then it is best to measure actual condenser air flow.
I would expect there to have condensers with at least 300m3/h air flow per 1kW of chiller cooling capacity.
I am not pulling these numbers from my head. They are numbers from technical data of McQuay chillers ALS “E” XE ST (HFC 134a)

http://www.mcquay.ru/downloads/ALS%20E_tm_en.pdf

XE in designation means that it is high efficiency heat exchanger (condenser) which is able to run up to 48°C ambient temperature, which should be used in your area.


Also, these data will let you know if it is problem with design (to small condenser) or with function of condenser.
To me, in this case, condenser is starting point.

Also, I would measure condenser air exit temperature to be able to calculate condenser approach!

When you lower that split to 10K-12K, I expect you will have no more problems with high DSH, if everything else is OK.
hi, nike .your observations are correct to me. Yes td is high. But in hot climate in dubai used td is maximum 17k.so the maximum condensing temperature should reach to 59c(331psig) at 42 ambient. Here discharge is high and check the subcooling is 12.therefore reducing gas charge to 8k sub cooling, can control discharge pressure and bring back the compressor amps to below compressor RLA 160 Amps. mayan Bhatia has to provide the readings of air entering and leaving temperature.

[RusBuka]

Place the liquid receiver. Fill up To 2-3 subcool.
Without economizer does not make sense.

[MayankBhatia]

As RusBuka mentioned, too high condensation temperature (for that ambient temperature) is on these records. Compressors are overloaded. High discharge temperature is result of that overload. Condenser split (TD) is 21,5K to 23K (according to records) which is excessive to me. I would expect, in that climate, to use high efficiency condensers with split of 10K, no more! What if ambient temperature go higher?

So I will be first checking if condenser is clean, fans are rotating in right direction and at proper rpm-s. If you have condensation control, than I would try to run fans at full speed with bypassing condensation control circuit. If you have condenser air-flow design data, then it is best to measure actual condenser air flow.
I would expect there to have condensers with at least 300m3/h air flow per 1kW of chiller cooling capacity.
I am not pulling these numbers from my head. They are numbers from technical data of McQuay chillers ALS “E” XE ST (HFC 134a)

http://www.mcquay.ru/downloads/ALS%20E_tm_en.pdf

XE in designation means that it is high efficiency heat exchanger (condenser) which is able to run up to 48°C ambient temperature, which should be used in your area.


Also, these data will let you know if it is problem with design (to small condenser) or with function of condenser.
To me, in this case, condenser is starting point.

Also, I would measure condenser air exit temperature to be able to calculate condenser approach!

When you lower that split to 10K-12K, I expect you will have no more problems with high DSH, if everything else is OK.


Thanks Nike for your detailed Observation.Condenser air Inlet and Outlet Difference is About 20-25Degree Celcius.

And is Condenser Split the same as of difference bw Condenser air and Out Temp?

[MayankBhatia]

hi, nike .your observations are correct to me. Yes td is high. But in hot climate in dubai used td is maximum 17k.so the maximum condensing temperature should reach to 59c(331psig) at 42 ambient. Here discharge is high and check the subcooling is 12.therefore reducing gas charge to 8k sub cooling, can control discharge pressure and bring back the compressor amps to below compressor RLA 160 Amps. mayan Bhatia has to provide the readings of air entering and leaving temperature.

i also Tried Taking out Some GAs From System so to have Subcooling Near about 8 but still no more effect.
But the thing is the refregeerant which need to be charge i didnot charge that much.as on name plate we should charge approx 70Kg but i charge near 40 Kg.

[RusBuka]

Can you post photo of info about chiller?

[moideen]

Thanks Nike for your detailed Observation.Condenser air Inlet and Outlet Difference is About 20-25Degree Celcius.

And is Condenser Split the same as of difference bw Condenser air and Out Temp?

25c is very high. It is tell us very clearly the air flow is not sufficient. No test is valid if the air flow is not correct. The condenser air delta temperature has to bring to the level of between 8c to10c

[MayankBhatia]

25c is very high. It is tell us very clearly the air flow is not sufficient. No test is valid if the air flow is not correct. The condenser air delta temperature has to bring to the level of between 8c to10c
Ok I will Measure the Air Flow and will revert. 1 thing what is correct method of measuring Air Flow in Air cooled Condenser? I mean i have Aneemometer i should place it near tip of fan then measure its velocity?

[Brian_UK]

Measure the size of the condenser coil face and use your anemometer on the coil face.