YVAA 1700 chiller. Condenser drain valve (EEV) control system

[Nemoralis]

Hello everybody,
I am a new member and this is my fisrt participation.
I appreciate if someone could explain or send information about the way that the condenser drain valve works in this type of chiller.
I guess that its control is based on the subcooling temperature (measured with the pressure transtucter and the probe, downstream the condenser (phase liquid refrigerant) but I think that the position of the valve depends on other parameters.
The Danfoss EEV (condenser drain valve) is connected to the Danfoss controller and the controller is connected directly to the main control board so I can not see the instrumentation involved in it.
Thanks in advance.

[stanbyyourword]

lots of posts about this on forum if you do search , will be clearer. yes It is on a subcooling value I an 90% sure.

[Nemoralis]

Thanks for your comments!
I was looking for a post about this issue but, unfortunately, I did not find anything about it.
I know the position of the valve depends on the subcooling temperature but I think that it depends on another parameter because being the subcooling setpoint 5ºC, the real subcooling can be between 8ºC and 11ºC with the position of the valve between 60% and 75% in estable position. For example subcoooling 9.8ºC and condenser drain valve 67%: the subcooling is not close to its setpoing and the valve does not move but the valve was checked and it works properly.
We have check everything and everything is right. We have several YVAA 1700 chillers and all of them are in similar situation. We think that something is not working properly but neither us nor the manufacturer know what is happening.
I think that the key of this issue is to know exactly how the EEV works.

[jayguy]

the main controller uses the liquid line pressure and temperature as inputs to a PID loop. the main controller then sends a 0-10 VDC signal to the Danfoss controller which then adjusts the valve accordingly. the condenser fans are also on a variable speed drive. if you look at that process, there are a lot of computers making a lot of decisions. add to it the chiller uses a microchannel coil. the microchannel coil is much more efficient and stores less refrigerant than a standard tube and fin coil. all of this can cause larger swings in the subcooled temperature. as long as you have some subcooled temperature, the swings aren't that big of a deal.

as always double check that your actual pressure measurements match the chillers display.

is there an issue with the chiller or are you just noticing the swings in subcooling?

[Nemoralis]

Thanks for your comments!
The condensation control in our chillers is very simple because they do not have VSD. They have the VSD only in the compressors; as you know YVAA 1700 has 2 system connected with an only one evaporator. So, when one system is working at full speed of hte compressor and all fans are working, the fans begin to stop if the compressor discharge pressure drops to 6.8barg; the fans will work again (all of them) if the discharge pressure reaches 11.5barg.
We are sure all transducters and probes are working properly because we checked them and, you know, it is easy to check them.
I think that the main control board considers other parameters in addition to the pressure transtucter and the temperature probe, downstream the condenser (phase liquid refrigerant) because after checking the instrumentation mentioned and the EEV with the resulf that everything is right, having a subcooling setpoint at 5ºC, the real subcooling can be, for example, 9,8ºC and the position of the EEV can be 67%. This does not make sense because the EEV should be opening to reach the setpoint (we checked the EEV and it is not stuck).
Are you sure that the only 2 parameters involved in the EEV control are liquid line pressure and temperatura?
Thank you very much!

[stanbyyourword]

the main controller uses the liquid line pressure and temperature as inputs to a PID loop. the main controller then sends a 0-10 VDC signal to the Danfoss controller which then adjusts the valve accordingly. the condenser fans are also on a variable speed drive. if you look at that process, there are a lot of computers making a lot of decisions. add to it the chiller uses a microchannel coil. the microchannel coil is much more efficient and stores less refrigerant than a standard tube and fin coil. all of this can cause larger swings in the subcooled temperature. as long as you have some subcooled temperature, the swings aren't that big of a deal.

as always double check that your actual pressure measurements match the chillers display.

is there an issue with the chiller or are you just noticing the swings in subcooling?

YVAA is the new RTAA?? haha hope youre well

[Nemoralis]

The manufacturer of the YVAA is Jonhson Controls / Roca and the manufacturer of the RTAA, I am not sure but I think that it is Trane.
Do you know anything about how the EEV of the YVAA chillers works?

[Chev5372]

As Jay said iOS looking at the two points for sub-cooling. The fans should stage up in pairs or be on a VFD and run together. Are the settings in the fan VFD correct. It gets a 0-10 VDC to drive the speed.


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[jayguy]

Thanks for your comments!
The condensation control in our chillers is very simple because they do not have VSD. They have the VSD only in the compressors; as you know YVAA 1700 has 2 system connected with an only one evaporator. So, when one system is working at full speed of hte compressor and all fans are working, the fans begin to stop if the compressor discharge pressure drops to 6.8barg; the fans will work again (all of them) if the discharge pressure reaches 11.5barg.
We are sure all transducters and probes are working properly because we checked them and, you know, it is easy to check them.
I think that the main control board considers other parameters in addition to the pressure transtucter and the temperature probe, downstream the condenser (phase liquid refrigerant) because after checking the instrumentation mentioned and the EEV with the resulf that everything is right, having a subcooling setpoint at 5ºC, the real subcooling can be, for example, 9,8ºC and the position of the EEV can be 67%. This does not make sense because the EEV should be opening to reach the setpoint (we checked the EEV and it is not stuck).
Are you sure that the only 2 parameters involved in the EEV control are liquid line pressure and temperatura?
Thank you very much!

those are the only 2 parameters that it should be looking at. you sat that you do not have vsd fan control. if that is true, it may look at ambient temperature or other pressures before it asks for the valve to move knowing that the subcooling is going to change when it changes the fans...but that is a big assumption.

[jayguy]

i checked the first software version and they do look at compressor VSD speed when making a decision to output to the drain valve as part of the PID loop. keep in mind that they are only controlling the valve...not the subcooling. the goal is that the subcooling will get inline. if you are having issues, your valve may WORK but not as fast as the PID loop is expecting it to work.

of course, there is a lot more logic behind all of this if the system is ramping up or down or bringing another compressor online or taking 1 offline.

[stanbyyourword]

Hi Jay do you have the sequence of operation for the staging and control logic of the valves and outputs etc? With actual values of temperatures and pressures? That would be super good resource to have as a reference if possible?

I was looking through the "service manual" thats pretty good I actually thought this was the IOM when I saved it

[Nemoralis]

Thank you very much for your help and comments.
It would be really interesting to have what you asking for. I do not have it but if anyboby can share it, that would be perfect!

[stanbyyourword]

if you email me i will send it

[Nemoralis]

Thank you very much Stanbyyourword.
I have just sent you an email.

[Nemoralis]

Does anyone have the control loop of the "condenser drain valve"? I would appreciate if anyone could send it to me.

[jayguy]

i am probably not supposed to have the software notes either, so i will not share them. sorry. i can look to confirm or deny specific issues like this if they arise if i know what software is being used and if i have those notes. i don't have notes of all software versions.

[Chillmac]

Some of the earlier vintage of YVAA did not have the VSD fan motors. They were either on or off. They had an extra two electrical enclosures on the side of the chiller, crammed with contractors. Typically two speed I think.
Make sure the valve is opening and closing correctly by driving it in service mode. Re-check all sensors and do you have a full charge of refrigerant?

[Nemoralis]

Hello jayguy,
Our software versión is "C.A03.23.00" and our VSD software versión is "C.V02.91.00"

[Nemoralis]

Hello Chillmac, thanks for your comments. We are really exhasted to check the temperatura probes and pression transductors and the condenser drain valve and all is right. On the other hand, to be sure the quantity of refrigerant (R134a) and oil (Suniso SL120) are right, we drained the system and we charged the system again, with 184kg of refrigerant (weighing it) and 19.7 liters of oil; those quantities are according to the manufacturer manual. After that, the behavior of the system is the same.

[Chillmac]

When you removed the refrigerant did you manually open the drain valve and economiser valves from the chiller control panel?
Is there any history of other work done on this machine?
Isn't your oil York 'L' oil?
Is your chiller tripping out on any particular faults?
Are both systems doing the same thing and do both system have the same pressure/temperatures etc when running? They won't be exactly the same but should be pretty close.