Soft Starter Issues

[HVAC_MY]

Hi
I have a RTHD Screw R123 Chiller rated at 300RT (Trane). The soft starter is a Benshaw ( Model:RBX-1-S-180A-15C ). Its around 5 years old.
The chiller was initially tripping intermittently (the chiller MCB located within the chiller panel) and the starter did not show any specific fault. We did a megger test (by a competent electrical person) and found one the studs to be faulty. Replaced all studs because the job is rather messy and long (the chiller is on a performance contract and every day it is down, we lose "savings").

After the studs was changed, we still have intermittent trips - the fault showed by the starter is basically phase error and SCR shorting. I am suspect that that moisture could be the problem as the chiller can run for a day or more and trips without warning. Why I say moisture is that there are traces of rust in the board (I noticed this when the wiring etc was removed).

I find that the solution of simply replacing the starter is not the best unless we can pinpoint the issue but as usual all suppliers love to change things when there is a small (and big) problem :)

I intend to "dry" the circuits using CO cleaner (for electronic) after switching off all power supply - is this advisable?

thanks in advance for any advice :)

[R123]

That starter will shunt trip the breaker anytime the starter faults on any alarm. If your truly getting a SCR shorting fault, the starter is probably bad.

Also, that chiller is R134A, not R123.

[HVAC_MY]

Thanks.. yes its a R134A. Sorry for the mix up. I have another Centravac R123, 2 stage centrifugal at the same site :).
But the error code was initially phase fault issue which was basically a false alarm as the rotation was fine and everything was checked before running. Than yesterday it show SCR shorting fault. The problem is that the chiller is able to start up, go on softloading and up to full load before tripping anywhere between 10 minutes to 7 days!

[jayguy]

...I intend to "dry" the circuits using CO cleaner (for electronic) after switching off all power supply - is this advisable?...

please use CO2 and not plain CO

[Healey Nut]

please use CO2 and not plain CO

Is CO available in an aerosol ??:angel::grin2:

[Screwit]

The SCR's of the Benshaw starter can be individually replaced if found to be faulty - As you are seeing random & intermittant faults related to/determined by phase measurement by the PCB I would be more concerned about your comment as underlined below.

1st question is why do you have moisture in the starter. You can remove the source of moisture but I suspect the damage may already be done




After the studs was changed, we still have intermittent trips - the fault showed by the starter is basically phase error and SCR shorting. I am suspect that that moisture could be the problem as the chiller can run for a day or more and trips without warning. Why I say moisture is that there are traces of rust in the board (I noticed this when the wiring etc was removed).

I find that the solution of simply replacing the starter is not the best unless we can pinpoint the issue but as usual all suppliers love to change things when there is a small (and big) problem :)

I intend to "dry" the circuits using CO cleaner (for electronic) after switching off all power supply - is this advisable?

[HVAC_MY]

Is CO available in an aerosol ??:angel::grin2:

it is CO2.. but the the brand CRC calls it CO... :). My bad ...again.. anxiousness in solving an expensive problem. I might resort to changing it to star-delta connection if possible because the chiller is on 24 hrs a day and is only shut down for maintenance works..but the client as usual have their preferences.

[GT Jets]

The SCR's of the Benshaw starter can be individually replaced if found to be faulty - As you are seeing random & intermittant faults related to/determined by phase measurement by the PCB I would be more concerned about your comment as underlined below.

1st question is why do you have moisture in the starter. You can remove the source of moisture but I suspect the damage may already be done

I have seen the CT's do this kind of stuff too, but it would typically go off on a ground fault alarm once in a while.

[HVAC_MY]

The SCR's of the Benshaw starter can be individually replaced if found to be faulty - As you are seeing random & intermittant faults related to/determined by phase measurement by the PCB I would be more concerned about your comment as underlined below.

1st question is why do you have moisture in the starter. You can remove the source of moisture but I suspect the damage may already be done

This is what I have been telling Trane - why is there moisture in the board? - the answer ..it is normal and no effect... the usual run-around, aversion to fault!

This is the fault (by the digital display) I noticed as the chiller operated (again dismissed by the service people):

a) warning voltage high at L1-L2 - i checked with a portable power meter (Fluke 1735) and trended it to detect any high voltage - none at all
b) Rotation error - this was not true as rotation was correct and my compressor did not fall apart :)

c) trip and now SCR short

The unfortunate thing is that there are no competent person to actually diagnose the problem - it is just guesswork and everyone loves to just replaced the entire component!

I believe it is the PCB that is faulty but cant replace the board - they want to change the whole starter!

[Healey Nut]

What kind of facility is the chiller in , is it used for a process chiller , is the atmosphere that the chiller is in the problem ? (moisture ,corrosion)
As far as fixing the problem, How many service calls are you willing to do before you could have just replaced the suspect part and be done with the issue ?

[HVAC_MY]

What kind of facility is the chiller in , is it used for a process chiller , is the atmosphere that the chiller is in the problem ? (moisture ,corrosion)
As far as fixing the problem, How many service calls are you willing to do before you could have just replaced the suspect part and be done with the issue ?

It is a 24 hour commercial cum data center building. The corrosion is basically due to condensation due to the cold surface - the chiller is located in the tropics so warm air is the norm here. Which is why I kept telling the supplier that that we need to do something - I am now considering coating panel surface with thermal insulation paint.

Well, we changed all 6 studs although only 1 was faulty - as a performance contractor we do not take shortcuts - the point of issue is that we were quite sure there was an issue with the starter but was told it was the studs or the MSB in the chiller panel. We actually told them to replace what is required or be ready with the replacement because one month of shutdown cost us around USD 25K in savings value - thus replacing faulty components is our target. Less service calls the better :)

I don't mind changing the starter but am contemplating of going for star delta since I dont need to start the chiller often....

[jayguy]

It is a 24 hour commercial cum data center building.....

it is a WHAAAT???

[stanbyyourword]

thats what i said :)

[GT Jets]

it is a WHAAAT???


Porn needs servers too...:cheers:

[cperk]

it is a WHAAAT???
Hey Jay! Sex sells you know.

[R123]

I guess thats where they catalog all the DNA for the crime lab....

[ryan1088]

Have you called Benshaw's tech support line yet? They are awesome, I suggest you do that first.

As for getting crazy sealing things, I have had great luck sealing flow switches and freezer conduit with a product called duct seal. It's a putty that you basically stuff in the hole around the wires.

http://m.lowes.com/pd_13591-12704-31-601_0__?productId=3127723

[Octopus]

How many feeders are fed into the plant from the utility ? Is there an voltage imbalance? Amprage imbalance?

[HVAC_MY]

How many feeders are fed into the plant from the utility ? Is there an voltage imbalance? Amprage imbalance?

2 feeders and i have checked the voltage - there is a slight imbalance but it has been like that for years - (its 415V here) - we are generally looking at 411, 412, 412 most of the time. The voltage fluctuates +-3 volts max.
There have been surges (voltage spikes once in a while).

[HVAC_MY]

Have you called Benshaw's tech support line yet? They are awesome, I suggest you do that first.

As for getting crazy sealing things, I have had great luck sealing flow switches and freezer conduit with a product called duct seal. It's a putty that you basically stuff in the hole around the wires.

http://m.lowes.com/pd_13591-12704-31-601_0__?productId=3127723

Thanks for the tip on the seals.

I have yet to call Benshaw. Will do that and update on the outcome here.

[HVAC_MY]

Hey Jay! Sex sells you know.
:)
http://en.wikipedia.org/wiki/Cum - depends which angle the mind is leaning towards :)...hahah

Sex does sell! :) got more attention than "chiller trip" :)

[Screwit]

2 feeders and i have checked the voltage - there is a slight imbalance but it has been like that for years - (its 415V here) - we are generally looking at 411, 412, 412 most of the time. The voltage fluctuates +-3 volts max.
There have been surges (voltage spikes once in a while).

"its 415v here, location in the Tropics, Centravac R123, 2 stage centrifugal at the same site" - so I assume with AFD if on 50hz supply, can I ask your location?

Also you have no details in your profile that assists the the decision to provide suggestions towards a resolve.

[Octopus]

Seen same thing the plant had two feeders. Primary and secondary if the primary feeder failed it switched and it tripped the chillers, had utility log site and he found an entire cap bank on one phase of the secondary shot, when they fixed the bank the plant was no longer problematic.

[jayguy]

Hey Jay! Sex sells you know.

oh, i know that...why do you think it takes me a long time to get around to logging in here! those girls aren't going to get through college by themselves!




TMI?

[cperk]

"its 415v here, location in the Tropics, Centravac R123, 2 stage centrifugal at the same site" - so I assume with AFD if on 50hz supply, can I ask your location?

.

Good eye Screwit! Should be 3 stage on 50 hz, due to the lower rpm of the motor.

[cperk]

TMI?

DING! DING! DING!

[Screwit]

Good eye Screwit! Should be 3 stage on 50 hz, due to the lower rpm of the motor.

The 2 stage CTV's can be applied on 400-415/3/50 power supply when using the AFD to convert to 460/3/60 supply to the motor. Just trying to figure out if this is close to home or not and how to help the OP. Can't recall RTHD & CVHF combination on a data centre in a tropical location down here so figuring it is somewhere else.

[HVAC_MY]

The 2 stage CTV's can be applied on 400-415/3/50 power supply when using the AFD to convert to 460/3/60 supply to the motor. Just trying to figure out if this is close to home or not and how to help the OP. Can't recall RTHD & CVHF combination on a data centre in a tropical location down here so figuring it is somewhere else.


Just updated my profile.

am located in Malaysia - its 50Hz electrical supply from the grid. Thanks for taking the effort :). Appreciate it.

I design energy efficient systems and not into specific maintenance. This particular site is a project that was started 7 years ago. We reduced the energy usage of the chiller plant from 300 kW to 150 to 180 kW (based on the load) by providing the required cooling tons and reducing pumping energy from 68 kW to 6 to 8 kW (again depending on load). The project was financed through bank loan and the contract is to last 10 years with the client receiving more savings as the year progresses.

What we do is that we measure the system continuously using our own hardware (i needed DACs that could take thermistors - accurate to 0.05 Deg C) and with one minute web based (java webstart) online monitoring with SMS warnings. With flow temperature and kW, approach etc I get up to date information on the system to ensure it runs.

All maintenance is done by the supplier of the equipment and there are no shortcuts - all items are changed as recommended (we even change solenoid valves that are goo as precaution - had a bad experience once!)

Hope the above description of the scenario helps :)

[TheChillerMan]

Moisture on the terminals of an RTHC/D is not unusual, especially in humid locations like South Florida. I've seen the terminals sweating while the chiller was running. Shut down the chiller, kill power and meg out the terminals to find 4 meg ohms to ground. Let it sit for a while, dry off the terminals and the meg ohms to ground go up to 100.

There should not be any moisture on the Benshaw starter itself. The terminals will get cold, and sweat when moisture is present, even if you seal up the starter cabinet. The cabinet is not weather/water tight. If the OP has moisture on the starter itself, there is some other issue going on.

If the OP is seeing a "phase error" that may be a phase loss? Which would make sense if he is seeing an SCR failure on the Benshaw. If it were me, I would replace the faulty SCR and go from there.

Benshaw starters are very reliable and easy to work on with their open chassis design.

The over priced Cutler Hammer/Eaton soft starters suck and always fail and you can't really work on them. But I digress....

[HVAC_MY]

Moisture on the terminals of an RTHC/D is not unusual, especially in humid locations like South Florida. I've seen the terminals sweating while the chiller was running. Shut down the chiller, kill power and meg out the terminals to find 4 meg ohms to ground. Let it sit for a while, dry off the terminals and the meg ohms to ground go up to 100.

There should not be any moisture on the Benshaw starter itself. The terminals will get cold, and sweat when moisture is present, even if you seal up the starter cabinet. The cabinet is not weather/water tight. If the OP has moisture on the starter itself, there is some other issue going on.

If the OP is seeing a "phase error" that may be a phase loss? Which would make sense if he is seeing an SCR failure on the Benshaw. If it were me, I would replace the faulty SCR and go from there.

Benshaw starters are very reliable and easy to work on with their open chassis design.

The over priced Cutler Hammer/Eaton soft starters suck and always fail and you can't really work on them. But I digress....

Thanks for the advice - yes makes sense on the phase loss warning - it keeps appearing before the chiller trips.
I have asked Benshaw for technical support in replacing the SCRs and a PCB board. Agree on the Cutler Hammer vs Benshaw. One of my other sites has a Cutler Hammer and we had some problems with it. Luckily it was a PCB card which was replaced.

[steveoo]

When you megged motor did you remove leads from soft start?

[HVAC_MY]

When you megged motor did you remove leads from soft start?

Hi

Yes, completely removed all connections including controls etc. we megged the studs connected to the motor (before and after) and the motor by itself

[R123]

we megged the studs connected to the motor (before and after) and the motor by itself

Are you saying you megged the soft starter terminals?

[HVAC_MY]

Nope. Not the softstarter. There studs connected to the motor - disconnected all wiring to the studs - from softstater , and megged the studs while attached to the motor. One of the studs resistance was very low. Megger was done by the supplier of the chiller.

[KnewYork]

Nope. Not the softstarter. There studs connected to the motor - disconnected all wiring to the studs - from softstater , and megged the studs while attached to the motor. One of the studs resistance was very low. Megger was done by the supplier of the chiller.When you say megger readings were low...how low? If you have a motor problem, why are you pointing at the starter?

[HVAC_MY]

When you say megger readings were low...how low? If you have a motor problem, why are you pointing at the starter?

I can't recall off hand how low it was. The motor is fine - it was one of the connecting studs. We actually removed the studs and checked the motor. The culprit is the motor.
The started is confirmed as the problem - but it could be the card or the SCRs. I have asked supplier to replace the SCRs as well instead of just the cards - as mentioned earlier, everyday the chiller is down, it is profit loss due to the nature of the shared saving contract

[Screwit]

RTHD CHHC compressor uses ceramic motor terminal insulators, if the ceramic is cracked moisture will enter (motor teminal is exposed to suction temperature which is below due point) causing a low insulation reading.

Good job identifying the correct fault - have seen motors condemmed by those with less experience due to motor terminal issues.

HVAC_MY you have the information I sent you to test the Silicone Controlled Rectifiers

[Healey Nut]

I can't recall off hand how low it was. The motor is fine - it was one of the connecting studs. We actually removed the studs and checked the motor. The culprit is the motor.
The started is confirmed as the problem - but it could be the card or the SCRs. I have asked supplier to replace the SCRs as well instead of just the cards - as mentioned earlier, everyday the chiller is down, it is profit loss due to the nature of the shared saving contract

So now were all totally confused is it the motor the starter the SCRs the insulators ??

[jayguy]

So now were all totally confused is it the motor the starter the SCRs the insulators ??

i thought i was reading that wrong too!

[milkyway]

We actually removed the studs and checked the motor. The culprit is the motor.
The started is confirmed as the problem - but it could be the card or the SCRs. I have asked supplier to replace the SCRs as well instead of just the cards -

??

[Screwit]

I you follow the entire thread pretty certain it is just a typo

The motor is fine - it was one of the connecting studs. We actually removed the studs and checked the motor. The culprit is the motor stud.
The started is confirmed as the problem - but it could be the card or the SCRs. I have asked supplier to replace the SCRs as well instead of just the cards

[milkyway]

HVAC certainly seems knowledgable ,. Must be a typo., good job Hvac for the diagnosis

[HVAC_MY]

HVAC certainly seems knowledgable ,. Must be a typo., good job Hvac for the diagnosis

Hi...sorry was busy and away. yes, type - the motor is fine, the stud was the issue. (the first issue of many to come :whistle:). I design chilled water system but get very involved in my projects and keep close eye on performance of the system. I am not a maintenance technician and therefore I listen and learn to ensure I make informed decisions. And forums such as this is heaven sent for me because in this part of the world, knowledge is not shared freely! Thanks to the forum I know I am on the right track.


The status as of today:

1) The Control board had damaged capacitors that were replaced. The coils on the card was ok - card tested and is working well
(I purchased a new board but that is now kept as a spare - plus the new boards have a different software version which means I will have to set the parameters which is something I want to avoid at this stage)
2) Replaced all SCRs (since there was a error reading indicating SCR shorted) - 2 SCRs has fluctuating ohm readings but was still within the required spec of 8 to 50 ohm. I was told that SCRs diagnostics is not straightforward. Replaced all SCRs as we cannot afford this issue cropping up again.
3) The started system is OK but there is an external fault which has been traced to the starter module. Removed for checking.

The root cause for the problem is probably a surge or shorted circuit - i.e. capacitors damages , SCRs damaged and now the starter module.

Will update the status.

[HVAC_MY]

So now were all totally confused is it the motor the starter the SCRs the insulators ??

Sorry guys - i type fast and miss out the finer words - it should be the motor studs - the culprit because it all started from there..but there were a lot of surge issues from the utility in the recent months. I cannot confirm if the surges damaged some components over time.

[HVAC_MY]

RTHD CHHC compressor uses ceramic motor terminal insulators, if the ceramic is cracked moisture will enter (motor teminal is exposed to suction temperature which is below due point) causing a low insulation reading.

Good job identifying the correct fault - have seen motors condemmed by those with less experience due to motor terminal issues.

HVAC_MY you have the information I sent you to test the Silicone Controlled Rectifiers

Thanks for the info. It was most helpful. I will take pictures of the system and the replaced parts once the system is up and running! :)

[Screwit]

Hvac_MY,

Thanks for the excellent feedback, it is appreciated by all who contribute to this site.

Thats is a lot of components to fail at once, if there are issues with the voltage supply it may pay to investigate surge suppression for the mains voltage supply as this will also assist with chiller up-time.

[HVAC_MY]

Dear All.

The problem was finally solved. To conclude (hopefully it helps others in the future)
1) Chiller had intermittent tripping - it could run for days and suddenly trip with error " Solid State Starter fault" at the LCD panel of the chiller - this is basically a feedback from the Trane Starter Card which detects the SSS starter electronic module (another electronic card) is not sending back an "OK" signal to allow start of the chiller. The SSS Control card had no specific error at this stage except warnings on voltage imbalance.
2) Trips became more frequent and eventually SCR error was observed at the SSS control card.
3) Decision made to check the motor winding and studs. One paid of Studs which are connected to the motor winding was found to have insulation problems after megger test. To confirm if it was the studs or the winding itself, the motor assembly was removed - the check proved that the studs were bad and (luckily) the winding were OK.
3) Although only 2 studs were confirmed to be faulty - we replaced all 6
4) SCR fault still appeared in the SSS Control Card
5) Techs suggested possible faulty control card but could not confirm - this was based on visual inspection where capacitors in the card were damaged. New Card was ordered. New Card was installed but the fault on the SCR appeared intermittently. The damaged card was sent for a "check-up" and damaged components was replaced.
6) All SCRs was replaced although the resistance test indicated they were OK. SCRs are hard to test and best to test when it is running - not possible in this case due to the fact the chiller could not start.
7) With all replaced, another round of testing and the error was a digital input. This was traced to the temperature sensor attached to the heat sink of the SSS. All contacts were cleaned and re-connected.
8) Chiller started and is in operation for the last 2 weeks.
9) The damaged SSS Control Card which was repaired is also working fine!

This was an problem that started from possible surges in power supply and components were affected.
A quick solution would have been to just replace the entire SSS - it was a choice and possibly the original SCRs are fine but we did not want to take any more chances.
A surge suppressor device is now sourced to avoid re- occurrence.


Special thanks to Screwit - exceptional individual who took the extra effort to help. Could not have solved the problem without his support. Invaluable advice that I used to direct the techs working on the chiller!

Benshaw - excellent service and quick communication

Thanks to all others who took the trouble to reply and provide advice :)

[BLohman]

Okay... once I got my mind out of the gutter... I've seen "competent" guys megger stuff w/o lifting the motor lead off the starter. Which is fine unless you have a soft start/vfd. You might have taken some damage during the megger process if the leads were still made up (which may have added another problem). As for the moisture... if you do dry/clean the components and that appears to correct the problem, then maybe consider installing a heater in the enclosure to control that moisture?

[HVAC_MY]

Okay... once I got my mind out of the gutter... I've seen "competent" guys megger stuff w/o lifting the motor lead off the starter. Which is fine unless you have a soft start/vfd. You might have taken some damage during the megger process if the leads were still made up (which may have added another problem). As for the moisture... if you do dry/clean the components and that appears to correct the problem, then maybe consider installing a heater in the enclosure to control that moisture?

Megger was done by taking off all leads. First megger was on the studs connected to the motor only. Since this could be a fault in the studs or the motor, we dismantled the studs to the motor. Motor megger was fine.

[BLohman]

Just out of curiosity... did you check the resistance between the different motor windings and find them equal/close? Not incredibly "scientific", but at least might help explain an unbalanced leg.