YORK suction limiting

[AlexG]

Hi.
I have York YAES0465 screw chiller running with Suction limiting message. LP setpoint is 1.5 bar, freeze setpoint is -7C (glycol), leavig water T setpoint is 7C. Message appeares when evaporating temperature is about 0C (LWT is about 9C)
***** R407C.Suction superheat is 6K, Cond Pressure about 16 bar.
Compressor doesn't load (47% current). Customer feels nervous.
What is the reason of limiting?

Alex

[Grizzly]

check your flow through your evaporator.
I surmise the comp software is limiting the suction because the load is inefficient.
IE poor flow through the evap!
If the lwt is only 2c off setpoint why load the comp further?
Or to put it another way the saturated suction temperature is to low and if it were to drop any further damage to the evaporator tubes is likely to occur. (Ice build upon tubes)
Grizzly

[yorkman_gr]

Alexander look at the manuals i have send it some time ago, just look at the options, it should say GLYCOL OPERATION, if not the unit is running as normal water chiller, if you read the manual you will see that water and glycol operation having a different LP cutting points and also different antifreeze point, if you need more ask Peter and i will cal you, for long time now i have troubles with my gmail and i need time to found out why, like i said ask Peter to give you my phone number

[Grizzly]

The original question is why is it suction limiting?
Grizzly

[yorkman_gr]

because when the chiller is working on water the low suction cut out is higher then is in glycol mode
All York chillers they work up to -9C but on glycol, if you forget to change the settings on glycol mode the chiller it will think that is working on normal water mode 12-6C and when the suction get near to the cutting set point the microprocessor it will try to prevent the unit of cutting off by unloading the compressors, also that it will happened if the discharge pressure is to high, it will limited the compressors to prevent cutting off. Also we have two different suction and antifreeze cutting points depends in which mode are you running. Of course i will not disagree with your point of view, everything is possible
PS: Also the set point on the chiller depends on the mode you running, normal water mode the set point it will never go under the antifreeze but when you running on glycol you can adjust your set point, antifreeze and low suction cut out

[yorkman_gr]

If everything is by the book i will think about flow, but also the unit contain two screw compressors what happen to the second one? same suction limiting? the LP cut off is 150Kpa which is -16C, the glycol freezing point is -7C and that to my opinion is to high, actually you should have the glycol freezing point about 4 degrees under your LP cut out point, 0C evaporating temperature is round 350Kpa suction pressure on 407c.Also i don't understand the set point is +7 or -7? Superheat of 6K is very good so enough refrigerant on the system, also i don't understand why on 0 evaporating temperature and with LWT +9 why the limiting,and with 6K superheat how more i read the details how more confused i get,

[Grizzly]

System 1 Suction limiting
System 2 Suction limiting


The message indicates that saturated suction
temperature on a system has dropped to a point where
any further temperature reduction could cause some
icing of the evaporator tubes. Saturated suction
temperature is calculated by the microprocessor by
converting suction pressure to temperature.

As quoted by York.
Alex you don't actually tell us what your suction pressure is?
What's the Liquid line sub cooling temp?
Also what is the Pressure diff across the evap?
Grizzly

[yorkman_gr]

Grizzly that is correct i have read the manual my self and is absolute correct, but the details that is given is confusing, hi said that the evaporating temperature is 0C so looking at the chart is equal to about 350Kpa, i am thinking that this units maybe they have a sensor to monitor the expansion temperature and maybe this sensor is out of range, also u said very correctly we don't know the DP across the evaporator, and the DT on the temperature, i hope it will give more details

[al]

Yorkman_gr

he wouldn't have been able to set the lower suction pressure unless it was switched to glycol setting, i'm with Grizzly on this, flow faults or expansion valve troubles, blocked driers etc..

alec

[yorkman_gr]

i said that before that you cant go lower on a set point if you don't change the deep switch 1 to glycol mode

[yorkman_gr]

also if you get blocked filter you will not have a superheat from 6K, txv defect also cant give you 6K superheat,that is at least what i have read on his post

[AlexG]

Hi Costas. Robin Peters sent me yoyr phone number. I will call you next week. This week I'm fighting with CIAT chillers, next week I will fight with York.
In my chiller in Option is glycol. It gives me to set negative antifreeze setpoint. All parameters are ok. It seams like somehting wrong with software.
Thanks in advannce.
Alex

[yorkman_gr]

Alex please make a running report and send it to my e-mail yorkman_gr@yahoo.com, it will help me a lot if i know more details about this trouble

[Grizzly]

It would be nice for all of us to know what is happening.
Grizzly

[yorkman_gr]

Grizzly dont worry i will inform you any way, if i get the running report from alex i will post it so we can look it together, I respect your knowledge about refrigeration like every body else, so don't worry i was planing to do so,regardless the company we work for bottom line we are all techs , only i hope i will get soon

[yorkman_gr]

Also the best thing is if you can find a serial to usb adaptor, to connected to RS 232 port, so you can use the hyper terminal to download all the details, and only if you got XP windows, the serial adaptor should be 9 pins, is like Robin doing with the PRIVA, if you will be able to find such an adaptor i will guide you how to connected on the chiller

Alex please make a running report and send it to my e-mail yorkman_gr@yahoo.com, it will help me a lot if i know more details about this trouble

[Grizzly]

Grizzly dont worry i will inform you any way, if i get the running report from alex i will post it so we can look it together, I respect your knowledge about refrigeration like every body else, so don't worry i was planing to do so,regardless the company we work for bottom line we are all techs , only i hope i will get soon

Thanks.
Then everyone can learn.
Grizzly