Unisab II control issues

[Mark II]

Hi All,

Fantastic site. congratuatons to those who put it together.. I joined late last year & have either been too busy or too slack to call in..(getting pretty hot here in Australia)

Having few drama's with a couple of Sabroe 163,s on VSD that wont operate in parralell. These units have Auto Vi & this seems to be the heart of the problem.
Individually i can run either comp in Remote & the Vi will follow the set point. In parralell the "A" comp Vi sits @ 0% Vi regardless of the set point & trips on capacity error (300 seconds). The "B"Comp (while "A" is running) will hold it's Vi @set point for a few minutes then proceed to ramp it's way up to 80% Vi & trip on Vi Position (even though the unisab otput is Negative 63%) At the moment i have "B" operating in remote."A" in manual (with the VI operating perfectly)..
I've tried Calibration of both Cap & Vi slides..
Can anyone offer any advice ??

[RANGER1]

Mark ,
Can you advise a bit more on the control philosiphy .
Does machines load up to 100% at min speed , then ramp up on VSD .
I know its a unisab II but how is Vi meant to control ? ie differential pressure across machine.
Why does Vi have to change all the time , is it a varying load ?

What conditions is it running at out of interest ?

Has it ever worked from new ?

[Mark II]

Ranger 1,

You are correct the Cap slides load to 100 % (showing 42% capacity @ 1500 rpm) The VSD then drives the comps up to 100% @ 3600 RPM. The control philosophy is: Once the lead is running @100% it calls the LAG & backs itself off to 55% & waits for the LAG to reach 55% also.. From there they mimic each other in parralell control.
Same goes in reverse, if they both back off to 55% one drops out & the other ramps up..
The auto Vi is controlled on suction superheat relative to discharge superheat. the thing that has me beat is the fact that it works perfecly on each compressor individually just not together..

[RANGER1]

Do you think it has ever worked from new ?
Do you have good litrature supplied with compressors giving all required info ?

Is there a sererate PLC that drives them or is it wholly Unisab II that you pick lead/lag and its meant to do the rest automatically ?

I'm sure there isn't to many of this type in OZ from Sabroe , most companies create their own with AB or similar PLC .
JCI are now offering Unisab III .
They say you can't stop progress but if you can create own programme with exactly what you want its got to be better than any of the over complicated Unisab and Frick Quantum panels .
These programmes are available in the local market anyway .
The trouble with Unisab and Frick is poor inhouse knowledge and back up in Australia, not to mention overpricing of them .

[Mark II]

Ranger1,

Has it ever worked from new ??

YORK Project with 2 years service deal.
Became JCI the day after it was installed & became a bunch of frickheads..

No PLC.. Plenty of detailed manuals..

I've looked into the Unisab III option..
As you say, expensive, and a maybe fix

Thanks for your efforts

[Grizzly]

Ranger1,

Has it ever worked from new ??

YORK Project with 2 years service deal.
Became JCI the day after it was installed & became a bunch of frickheads..

No PLC.. Plenty of detailed manuals..

I've looked into the Unisab III option..
As you say, expensive, and a maybe fix

Thanks for your efforts

Mark.
Your post raises many questions.
Basically I am not sure it is simply your terminology that is confusing me.
Or you do indeed have a fundamental problem.
A 163 rotatune has it's slide capacity fixed and on certain models there is no capacity slide.
Capacity is controlled by means of changes in motor revolutions.
Read on the multisab as Motor Capacity or within the Motor Picture as number of revolutions.
Secondly if there is more than 1 rotatune within a system. the unisab must follow the compressor with the lowest start number.
As there is a Master Slave control sequence in operation.
It does indeed sound like you have a control issue.
If you have the manuals could you not check your Unisab / Vacon settings.
You could have a site "finger poker" been known before!
Good luck, as much as it may hurt you may well have to talk to Johnson's.
But ask for their controls guy or at least someone who knows Sabroe controls.

Unisab is a brilliant piece of kit and the unisab III appears to be better than II.
But like all thinks they are only easy if you know how to use them?

Keep asking the questions and you will get there.

Grizzly

[charlie n]

The only guys who really know Unisab are in Denmark. I was involved in the development of the first Unisab back in the early 90's & we often did "field testing". Often without intending to. The point being that while Unisab is a great controller when it's programmed correctly, it's quite complex and there can be unforseen glitches. Describe your problem to the control guys in Denmark & I'm sure they will find the problem & help you fix it.

[Andy]

Ranger 1,

You are correct the Cap slides load to 100 % (showing 42% capacity @ 1500 rpm) The VSD then drives the comps up to 100% @ 3600 RPM. The control philosophy is: Once the lead is running @100% it calls the LAG & backs itself off to 55% & waits for the LAG to reach 55% also.. From there they mimic each other in parralell control.
Same goes in reverse, if they both back off to 55% one drops out & the other ramps up..
The auto Vi is controlled on suction superheat relative to discharge superheat. the thing that has me beat is the fact that it works perfecly on each compressor individually just not together..

I suppose the easy answer is run rhe compressors as stand alone and set the suction pressure slightly differently.
That is until you have an answer on the auto VI.

Kind Regards Andy

[Mark II]

Grizzly,

The Cap slide is not fixed on these units. The slide position is only visible within the capacity screen. Overall output on the main screen is a combination of both Cap Slide & VSD.
Having said that, the system always has enough load to exceed 100% slide capacity & is virtually controlled totally by the VSD.

I have no problem calling in JCI, However the last time their Guru was here training our operators on our new Quantum system. He removed the back-up stick / wiped the program/ left us with a touch sreen default program on a non touch screen panel..
They had no back-up.. No clue & we were down one system for 6 weeks..
When we did get the back-up we were left to manually input all the set points..

I'll take your advice & look into the Vacon settings though. CHEERS

[Grizzly]

Grizzly,

The Cap slide is not fixed on these units. The slide position is only visible within the capacity screen. Overall output on the main screen is a combination of both Cap Slide & VSD.
Having said that, the system always has enough load to exceed 100% slide capacity & is virtually controlled totally by the VSD.

I have no problem calling in JCI, However the last time their Guru was here training our operators on our new Quantum system. He removed the back-up stick / wiped the program/ left us with a touch sreen default program on a non touch screen panel..
They had no back-up.. No clue & we were down one system for 6 weeks..
When we did get the back-up we were left to manually input all the set points..

I'll take your advice & look into the Vacon settings though. CHEERS

Hi Mark.
Thanks for the prompt reply.
You must have quite a variety of comps there?
Quantum is for Frick systems is it not!
Or are there Sabroe Units on these?
Well we must be working from different Manuals Mark.
Because all the info I have states that the 163R (rotatune variable speed drive) is manually fixed!
That is for the Mk4's I shall have to get my manuals out to check on the Mk3's but I am pretty sure they are the same?

Like I say you may have something quite special.
Just trying to help with your issues if what you have is as it should then so be it!

From what others have told me you may well have a shortage of "Gurus"!
The one you mention doesn't sound to clever.
Why 6 weeks delay?
Good Luck anyway.
Grizzly

[Mark II]

Grizzly,

We upgraded 2 of our plants here 18 months apart.. The Sabroe package went in 1st & the Boys had York shirts on.. When they came back they had JCI shirts & were pushing FRICK.. I would have loved to have kept both plants the same..

The manuals i have been provided are not specific to my plant. I have 5 Bible size volumes that cover the entire product range & quite often the instructions & proceedure are interwoven in a way that makes them very difficult to follow..

I'm going to have to do some homework.. These comps are Mk IV's & as you say should run fixed capacity..

Cheers