York Chiller

[N.Lewis]

Hi Guy's.
Any help here most welcome, i'll try and give as much info in one hit as poss!!
Air cooled water chiller Mod:ycaj55. Ref 407C
Unit keeps tripping on low suction:
Suc press 3.65B
Diss press 15.7B
Chilled liq 31.7degC
Water flow temp 6.1degC
Oil press 6B
Oil temp 34.0degC
On checking unit found two leaks, one on comp diss stem, and other on core drier service valve, repaired both, also replaced X2 core driers in case of blockage, but unit still only runs for aprox 20mins then trips again:confused:

[nike123]

What is setting of low pressure switch or what is reading of low pressure probe? Does low pressure control circuit have any other safety device?
Am I reading correct, that chilled liquid outlet is 25,6°C?

[N.Lewis]

Hi nike123.
Low press switch is small electronic one attached to suc valve, don't know if you can obtain a reading for setting off of these!! I got chilled temp reading off digital display on unit, as far as i am aware this only safety devise, so far unit is still running, don't you find that all readings i gave sound o.k, V.puzzling!! I know it sounds odd, but i have come accross this prob before and found just changing water temp probe solved prob:eek:

[nike123]

If outlet water temperature is 25,6°C than your suction saturation temperature is low (0,6°C). It should be around 10°C. Then again, that suction pressure (3,6Bar) should not trigger low pressure alarm.

[lalthomas]

Have u topped any gas after rectifying the leakages? Your chiller may require some topping to compensate the gas leaked out.
cheers..
Lal Thomas

[N.Lewis]

Hi lal, yes mate topped unit up, and it's still running, been two hours now:).

Cheers Nick.

[nike123]

Hi lal, yes mate topped unit up, and it's still running, been two hours now:).

Cheers Nick.

Now, you should check subcooling! That temperatures don't look OK to me! Maybe your gauges needs adjusting.

[philjd26]

hi,
407c guys.. you cant be topping you must reclaim gas and charge up with a fresh one....you could be getting ok suction presssure but evap temparture would be very low due to a component from blend lacking causing a 410a symtoms..

rgrds phil

[nike123]

Hi, philjd26!

You are partialy right! That also depends where leak is occurred and how big is it.
Here we have two leak points, one is at "good" point (compressor discharge stem) and other is at "bad" point "core drier service valve".
It is possibility that composition is not significantly changed and with toping small amount (5-10%) he could regain to normal operating conditions.
If that amount is larger than that, I will recover all refrigerant, pressure test chiller and then charge by weight.

It is not necessary to always be in "panic mode" and change all refrigerant when ever is leak at R407C system.

My practice is based at this study ( http://tinyurl.com/2mqydb )and I did not have any problems with this approach.

This is part of conclusion of that study:

8.2 RECOMMENDATIONS FOR FUTURE WORK
This research work focused on the effect of leak on the system performance and system
reliability as well as its adverse effect on system maintenance and cost associated with
tackling complexity of leak in the systems charged with zeoptropic refrigerant blend. As
these systems, in the event of leak, can not be simply topped up with refrigerant, it
introduces major challenges to the industry dealing with this issue. The chiller systems
contain significant amount of refrigerant due to its shear size and capacity. Any
complete refrigerant replacement would be a costly exercise. This work showed that,
depending on the system and efficiency and safety sensitivity, leaks up to about 10-20%
can be tolerated by just topping up the system charge with R407C. This is due to the
fact that the efficiency and characteristic change of the system would be minimal.

Best regards,

Nike.

[narkom]

The compressor on this chiller has 4 stages of loading. So if on the first stage everything is OK, on the fourth stage the system may trip on low suction. You should check the ref. charge on all the stages. What is the low suction trip point ?

[jason09]

where u say Chilled liq 31.7degC , i assume thats the liquid line temp out of condenser is that right? and 6degc leaving chilled water temp? whats the entering chilled water temp? and suction temp? how many stages are loaded i imagine your trying to maintain 6deg leaving water temp? are you sure the system is nt just cycling, you said it trips do you need to resset it or does it just time out and restart

[al]

hi

It looks as if you have a faulty leaving water temp sensor, if actual temp is 6c and panel thinks its 31c it will try to cool to it to 6c and consequently trip on low suction pressure which is 3.3B for non glycol setting.

Is it electronic or standard txv?

regards

alec

[Grizzly]

Guys have you noticed Nick himself says he sorted the problem on the 4-2-08 by topping the system up with refrigerant.
But may I just agree with Alec York LWT Probes sometimes leave a lot to be desired and it is not unknown for them to fail.
I have seen a system where various engineers had diagnosed a refrigerant shortage due to LP Cutouts.
When the system was later found to be overcharged by 20kg. A faulty LWT Probe was the culprit.
Grizzly

[frank]

Hi Guy's.
Any help here most welcome, i'll try and give as much info in one hit as poss!!
Air cooled water chiller Mod:ycaj55. Ref 407C
Unit keeps tripping on low suction:
Suc press 3.65B
Diss press 15.7B
Chilled liq 31.7degC
Water flow temp 6.1degC
Oil press 6B
Oil temp 34.0degC
On checking unit found two leaks, one on comp diss stem, and other on core drier service valve, repaired both, also replaced X2 core driers in case of blockage, but unit still only runs for aprox 20mins then trips again:confused:
My advice here Nick would be to disable the existing LP switch and put in a temporary Ranco or similar with a small capillary connection and see if the chiller still trips.

It sounds like it could be a d!cky LP switch.

I had a YCAC lose a compressor because of a faulty MOP tev. It would close down intermittently - especially when I wasn't on site - and the result would be a low suction pressure, just above the LP setting leading to the compressor overheating.

Was talking to the customer one day at the machine and scratching my head thinking what the elusive problem was when all of a sudden the suction began serious frosting. Changed the TEV and it's been running OK since.