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  1. #27
    Join Date
    Sep 2008
    Location
    A land down under
    Posts
    314
    Quote Originally Posted by cperk View Post
    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.
    Necessity is the mother of invention

  2. #28
    Join Date
    Mar 2011
    Location
    Malaysia
    Posts
    32
    Quote Originally Posted by Screwit View Post
    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

  3. #29
    Join Date
    Mar 2011
    Posts
    260
    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....

  4. #30
    Join Date
    Mar 2011
    Location
    Malaysia
    Posts
    32
    Quote Originally Posted by TheChillerMan View Post
    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.

  5. #31
    Join Date
    Dec 2011
    Posts
    108
    When you megged motor did you remove leads from soft start?

  6. #32
    Join Date
    Mar 2011
    Location
    Malaysia
    Posts
    32
    Quote Originally Posted by steveoo View Post
    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

  7. #33
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,368
    Quote Originally Posted by HVAC_MY View Post
    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?

  8. #34
    Join Date
    Mar 2011
    Location
    Malaysia
    Posts
    32
    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.

  9. #35
    Join Date
    Jan 2011
    Posts
    1,223
    Quote Originally Posted by HVAC_MY View Post
    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?

  10. #36
    Join Date
    Mar 2011
    Location
    Malaysia
    Posts
    32
    Quote Originally Posted by KnewYork View Post
    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

  11. #37
    Join Date
    Sep 2008
    Location
    A land down under
    Posts
    314
    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
    Attached Images Attached Images
    Necessity is the mother of invention

  12. #38
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,110
    Quote Originally Posted by HVAC_MY View Post
    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 ??
    The toy chest is officially full ... I got a new toy..... 2007 Aston Martin V8 Vantage
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  13. #39
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,524
    Quote Originally Posted by Healey Nut View Post
    So now were all totally confused is it the motor the starter the SCRs the insulators ??
    i thought i was reading that wrong too!
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

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