Frick Quantum LX Compressor control panel: Capacity Control Screen

Hi All
I have been looking at Frick Quantum LX compressor control panel's operation service manual. In its Capacity control Screen description, they have the following parameters:

Setpoint : 20 PSIG (just example numbers used in manual)

HIGH LOW
Proportional Band: 15 PSIG 15 PSIG
Dead Band : 0.5 PSIG 0.5 PSIG
Cycle Time : 3 SEC 3 SEC

Channel: Suction Pressure

According to the description of each field and the numbers they used, i am a little confused here. Do these numbers mean as follows:

if my sp is at 20 PSI then the dead band high would be set at 20+0.5 = 20.5 PSIG and the Proportional band high would be set at 20.5+15 = 35.5 PSIG (set above the dead band high). Also if lets say my suction pressure actual reading is 40 PSI (assume) which would be beyond my proportional band high value(35.5) , i have to energize my load solenoid all the time. Also what does that cyle time mean?

After reading the description on their service manual, i am really confused how actually loading and unloading works in their control panels. If someone can explain to me within the context of the numbers they have used in their service manual, i will really appreciate it. Here is the their service manual number S90-022 O

It didn't let me post the link to above manual, but if you google the above number, you will be able to find that manual.





Thanks in advance

Hi Screw Geek,

I'm not an expert on these controls but have had a quick look at the manual, link here...
http://www.frickcold.com/documents/library/1275.pdf

Looking at page 11 the unload description seems to go like this, I think :)

If the master compressor’s Suction Pressure is above
the Capacity Control setpoint, the master calculates
the increase in capacity that is required. The
calculation is as follows:
Difference = Suction Pressure – (Capacity
Control Setpoint + Upper Dead Band)

Using your figures...
Difference = 40psi - (20psi + 0.5psi)
= 40 - 20.5
= 19.5
Diff is greater than Upper Band

If the Difference is less than the Upper Proportional
Band:

Capacity Change = (Difference / Upper
Proportional Band) * Upper Cycle Time

Therefore
Change = (19.5 / 15 ) * 3secs
= 3.9

If the Difference is greater than the Upper
Proportional Band:

Capacity Change = Upper Cycle Time
= 3secs

And it appears that depending on the exact model being used the Capacity Change is added to the compressor(s) loading or a direct Load Pulse is given.

I hope this helps a little.

Quote:

---

Originally Posted by Brian_UK

Hi Screw Geek,

Looking at page 11 the unload description seems to go like this, I think :)

If the master compressor’s Suction Pressure is above
the Capacity Control setpoint, the master calculates
the increase in capacity that is required. The
calculation is as follows:
Difference = Suction Pressure – (Capacity
Control Setpoint + Upper Dead Band)

Using your figures...
Difference = 40psi - (20psi + 0.5psi)
= 40 - 20.5
= 19.5
Diff is greater than Upper Band

If the Difference is less than the Upper Proportional
Band:
Capacity Change = (Difference / Upper
Proportional Band) * Upper Cycle Time

Therefore
Change = (19.5 / 15 ) * 3secs
= 3.9

If the Difference is greater than the Upper
Proportional Band:

Capacity Change = Upper Cycle Time
= 3secs

And it appears that depending on the exact model being used the Capacity Change is added to the compressor(s) loading or a direct Load Pulse is given.

I hope this helps a little.

---

Thanks
Also if u have some time and if u take a look on page 24 of this manual, they talked abt a Cyle Time. Do they mean to capture a suction value for the calculations after every cyle time is complete? that's the confusing part. If you guys can elaborate this, it helps a lot.

Regards

Let me try. Frick panels are a bit complicated in comparison to some.
Forgive me if I do not get this exactly, as I have not worked on a Quantum in a while.

Dead band is a range during which the compressor will not load or unload. if set at 0.5 it will not load or unload the compressor unless suction pressure goes above or below the suction setpoint by this much.

Cycle time is the amount of time that the load/unload solenoids are energized within the Proportional Band.

Proportional band is the area in which the panel sends short pulses to the solenoids. Outside the proportional band the solenoids are energized all the time, until the suction moves within the proportional band. It serves to keep the suction pressure stable, rater than rapid unneeded loading/unloading.

Clear as mud?:)

This is the link. There are a couple of other manuals on the panels in there you might want to look at as well.
http://www.frickcold.com/documents/library/1275.pdf

Hi, Screw_geek :)

Quote:

---

Originally Posted by screw_geek

....
Setpoint : 20 PSIG (just example numbers used in manual)

HIGH LOW
Proportional Band: 15 PSIG 15 PSIG
Dead Band : 0.5 PSIG 0.5 PSIG
Cycle Time : 3 SEC 3 SEC

Channel: Suction Pressure

According to the description of each field and the numbers they used, i am a little confused here. Do these numbers mean as follows:

if my sp is at 20 PSI then the dead band high would be set at 20+0.5 = 20.5 PSIG and the Proportional band high would be set at 20.5+15 = 35.5 PSIG (set above the dead band high). Also if lets say my suction pressure actual reading is 40 PSI (assume) which would be beyond my proportional band high value(35.5) , i have to energize my load solenoid all the time. Also what does that cyle time mean?

Thanks in advance

---

According to your values:

SP=20 psig
NZ= 0.5 psig 0.5 psig
PB= 15 psig 15 psig
Cycle time 3 sec 3 sec

Seems you can set you NZ as you like around SP and the same is for PB. Time to engage solenoids you can also change up maybe from 0.5 sec up to 3 sec both for up and down.
You must play with those values but you can try

SP=20
NZ= 0.5 psig 0.5 psig
PB= 5 psig 5 psig
time down 3 sec time up 2 sec

Once you set your NZ and PB it will come along with any SP you set.

Please take a look at attached file:

Best regards, Josip :)

Josip;
Nice PDF. A picture can be better than a thousand words!
Did you make that up?

Thanks a lot guys, just one final thought to discuss:

So the cycle time up means total load time for the compressor, for example If cycle time up and other parameters set as follows:

Cycle time up = 3 sec
Proportional Band = 15 Psi
NZ = 0.5 Psi
SP = 20 Psi
Actual value = 35 Psi

Then Difference = Actual Value – (SP+NZ) = 35-(20+0.5)= 14.5 Psi (for loading)

If Diff < PB Then
Capacity change = (14.5/15) x 3 = 2.89 sec


Therefore, the load solenoid will be ON for 2.89 sec and off for (3-2.89) = 0.1 sec. Is it correct? The above calculation will be valid for 3 sec. Once the 3 seconds elapsed, a new value of suction pressure will be captured and the above calculation will be generated, is it correct also? Or the above calculation will be taking place continuously until the suction pressure meets the SP. The way i understood cycle time is that,there is a cycle time up or down timer that will be resetting automatically once the .acc value becomes equal to .pre value (3 sec in this case), and from the start of the new cycle it will reevaluate the response and actual value.

Regards

Hi, NH3LVR :)

Quote:

---

Originally Posted by NH3LVR

Josip;
Nice PDF. A picture can be better than a thousand words!
Did you make that up?

---

Thanks.

Yes, agree with you we have to use drawings whenever is possible.

Partially, lines and letters within are copy-paste;) , but letters under picture are mine to describe the drawing.

Best regards, Josip :)

Hi, Screw_geek :)

Quote:

---

Originally Posted by screw_geek

Thanks a lot guys, just one final thought to discuss:

So the cycle time up means total load time for the compressor, for example If cycle time up and other parameters set as follows:

Cycle time up = 3 sec
Proportional Band = 15 Psi
NZ = 0.5 Psi
SP = 20 Psi
Actual value = 35 Psi

Then Difference = Actual Value – (SP+NZ) = 35-(20+0.5)= 14.5 Psi (for loading)

If Diff < PB Then
Capacity change = (14.5/15) x 3 = 2.89 sec


Therefore, the load solenoid will be ON for 2.89 sec and off for (3-2.89) = 0.1 sec. Is it correct? The above calculation will be valid for 3 sec. Once the 3 seconds elapsed, a new value of suction pressure will be captured and the above calculation will be generated, is it correct also? Or the above calculation will be taking place continuously until the suction pressure meets the SP. The way i understood cycle time is that,there is a cycle time up or down timer that will be resetting automatically once the .acc value becomes equal to .pre value (3 sec in this case), and from the start of the new cycle it will reevaluate the response and actual value.

Regards

---

About this I do not know because I am not familiar with Quantum controller. My previous picture is from another controller.

For me it seems something here is missing (we call that step delay=time to measure actual set point) and then to issue another signal (to engage solenoid) which can be now to reduce the capacity.

This must be PID controller with P-proportional, I-integral and D-derivative functions with feedback signal. The algorithm is different for different controllers.

You should check that in manual for that controller

,but as per my experience you must run your plant and see what happen and for sure you must make some fine tunning either for P,I or D values. Otherwise your compressor you can set to be a "hunter". This is more like a game do not be afraid;)

Best regards, Josip :)

Quote:

---

Originally Posted by Josip

Hi, Screw_geek :)


About this I do not know because I am not familiar with Quantum controller. My previous picture is from another controller.

For me it seems something here is missing (we call that step delay=time to measure actual set point) and then to issue another signal (to engage solenoid) which can be now to reduce the capacity.

This must be PID controller with P-proportional, I-integral and D-derivative functions with feedback signal. The algorithm is different for different controllers.

You should check that in manual for that controller

,but as per my experience you must run your plant and see what happen and for sure you must make some fine tunning either for P,I or D values. Otherwise your compressor you can set to be a "hunter". This is more like a game do not be afraid;)

Best regards, Josip :)

---

Hi Guys
Sorry for the late reply. Well for Josip comments, if i have two discrete outputs to control, how can i use PID controller to control outputs, as for as i know you can only control analog outputs out of PID controller

Hi, screw_geek :)

Quote:

---

Originally Posted by screw_geek

Hi Guys
Sorry for the late reply. Well for Josip comments, if i have two discrete outputs to control, how can i use PID controller to control outputs, as for as i know you can only control analog outputs out of PID controller

---

I'm sorry I do not understand what you mean;) (maybe due to my english;) )

Why you need to control outputs from PID controler:confused:

Best regards, Josip :)

Quote:

---

Originally Posted by Josip

Hi, screw_geek :)



I'm sorry I do not understand what you mean;) (maybe due to my english;) )

Why you need to control outputs from PID controler:confused:

Best regards, Josip :)

---

Well what i meant to say is that, i have two discrete outputs to control: Load solenoid and unload solenoid. The method you suggested in your last msg was to develop some sort of PID controller to control loading or unloading sequence. thats why i asked this. Hope that clears......

Hi, screw_geek :)

Quote:

---

Originally Posted by screw_geek

Well what i meant to say is that, i have two discrete outputs to control: Load solenoid and unload solenoid. The method you suggested in your last msg was to develop some sort of PID controller to control loading or unloading sequence. thats why i asked this. Hope that clears......

---

No, you have your set point (pressure, temp) and you have to instruct your PLC how to reach that point, thus tell him about proportional bad, I-time meaning time to come to your set point, slower or faster response and controller will issue needed signal for loading/unloading accordingly. Derivative function we use to smooth output regulating signal.

We have to set one good proportional band not too wide nor narrow, some good sample time (means when repeat to read actual point and then issue an regulating signal up/down, usually I-time is bigger if system response is slower and vice versa, and we have derivative function to shape output signal meaning as reading/input signal is close to set point regulating/output signal will be smaller and within dead band there will be no signal.

You have nothing to control, for that you have your controller which must be programed good.

Hope this give some picture;)


Best regards, Josip :)

Quote:

---

Originally Posted by Josip

Hi, screw_geek :)



No, you have your set point (pressure, temp) and you have to instruct your PLC how to reach that point, thus tell him about proportional bad, I-time meaning time to come to your set point, slower or faster response and controller will issue needed signal for loading/unloading accordingly. Derivative function we use to smooth output regulating signal.

We have to set one good proportional band not too wide nor narrow, some good sample time (means when repeat to read actual point and then issue an regulating signal up/down, usually I-time is bigger if system response is slower and vice versa, and we have derivative function to shape output signal meaning as reading/input signal is close to set point regulating/output signal will be smaller and within dead band there will be no signal.

You have nothing to control, for that you have your controller which must be programed good.

Hope this give some picture;)


Best regards, Josip :)

---

Hi Josip
So if i have to make an analagy of your graph (a pdf document that you posted in the beginning of the thread) with the capacity control screen in frick control panel then it will be something as follows:

FRICK PANEL Graph

Proportional band = Proportional band
Cyle time = Integral time
Dead band = Neutral band

Just to let you know that compressors that i am dealing with don't have frick panel installed with them. they are purely based on a customized PLC panel, plc programming would be my job. I am just looking at different options for slide valve capacity control algorithms in different manufacturers panels.

I dont have enough information to begin programming on this part, so i am just working around different ideas or options i could possibly have.

When i looked at the firck capacity control algortihm, it looked pretty close to me what i will be doing. Since i dont have any experence with screws and with frick panel thats why i tried to explore them with the help of you guys.

frick algorithm is looking pretty simple to me ( unless something complexed going at the back end which i am not aware of).All its doing is calculating the error signal after every cycle time and based on that error signal, calculates the capacity change...hope this will give you more clear idea of what i am going after for.

Regards
Pro

Hi, Screw_geek :)

You are in a deep water now;)

Quote:

---

Originally Posted by screw_geek

Hi Josip
So if i have to make an analagy of your graph (a pdf document that you posted in the beginning of the thread) with the capacity control screen in frick control panel then it will be something as follows:

FRICK PANEL Graph

Proportional band = Proportional band
Cyle time = Integral time
Dead band = Neutral band

Just to let you know that compressors that i am dealing with don't have frick panel installed with them. they are purely based on a customized PLC panel, plc programming would be my job. I am just looking at different options for slide valve capacity control algorithms in different manufacturers panels.

I dont have enough information to begin programming on this part, so i am just working around different ideas or options i could possibly have.

When i looked at the firck capacity control algortihm, it looked pretty close to me what i will be doing. Since i dont have any experence with screws and with frick panel thats why i tried to explore them with the help of you guys.

frick algorithm is looking pretty simple to me ( unless something complexed going at the back end which i am not aware of).All its doing is calculating the error signal after every cycle time and based on that error signal, calculates the capacity change...hope this will give you more clear idea of what i am going after for.

Regards
Pro

---

I'm not very familiar with quoted expressions and exact meanings, i.e. the same expressions can be used for different meanings:confused:

but...

Dead band is Neutral band no change in capacity no regulating signals but with minor error signal

Proportional band is an area with proportional regulating signal meaning if you are far from set point that signal will be stronger

I-time is time within we want to reach to set point what depend on system, direct or indirect cooling, etc

Cycle time or sampling time i.e. reading time for reading of real working point-set point=error signal. this time we need to get back response of system to our previously issued regulating signal, we do not have a real time response and we have to wait. This also depend on type of system.

But according to your post you are on good way;)

Do not worry about different algorithms, with different approaching your solution/algorithm will be different;)

Best regards, Josip :)

Quote:

---

Originally Posted by Josip

Hi, Screw_geek :)

You are in a deep water now;)




I'm not very familiar with quoted expressions and exact meanings, i.e. the same expressions can be used for different meanings:confused:

but...

Dead band is Neutral band no change in capacity no regulating signals but with minor error signal

Proportional band is an area with proportional regulating signal meaning if you are far from set point that signal will be stronger

I-time is time within we want to reach to set point what depend on system, direct or indirect cooling, etc

Cycle time or sampling time i.e. reading time for reading of real working point-set point=error signal. this time we need to get back response of system to our previously issued regulating signal, we do not have a real time response and we have to wait. This also depend on type of system.

But according to your post you are on good way;)

Do not worry about different algorithms, with different approaching your solution/algorithm will be different;)

Best regards, Josip :)

---

Hi Josip
Thanks for your guidence. Hopefully, once i have all the information, i will be able to program a good controller :(

Hi, screw_geek :)

Quote:

---

Originally Posted by screw_geek

Hi Josip
Thanks for your guidence. Hopefully, once i have all the information, i will be able to program a good controller :(

---

Hope you will not misinterpret this;) : you must know how your system/compressor must work to achieve what you need, then you can write down a good program.

Of course no need to repeat some mistakes and for that step you can use some other algorithms to guide you.

You can send me PM with your email address and I will send you some pdf files to get some old (but good) ideas;)

Best regards, Josip :)

Has anyone known the level password for the Frick Quantum LX compressor?

The level 1;password:10
The level 2;password:20
The level 3;password:??
The level 4;password:??

Please help me, thank you!