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  1. #1
    Join Date
    Apr 2006
    Location
    Columbus, Ohio
    Posts
    809

    Trane RTAA Severe Phase Imbalance

    I have a Trane RTAA Chiller tripping on the severe phase imbalance about twice a week. It is tripping out both circuits when this happens. It is usually very early in the morning. Usually compressor A will trip first, and then about 6 min later compressor C trips off. The fact that both are tripping around the same time I assumed that there was a power problem. After checking the voltages i noticed a imbalance, and higher than normal voltages. We called AEP, and they told us that they had a bad voltage regulator on the main lines into the building. After they changed it out the power appeared to be normal. Well the chiller went back down again yesterday. Is there something I can do about this? Everytime this thing goes down the Tracer calls the customer. The tenants in the building are getting upset. What can I do? Is there some other things I can check? I already checked all of the connections, and ohmed out the current transformers. I checked the contacts on the starters, and the compressor terminals. To me since the electric company had the problem before, they may still have a problem, but they claimed that they fixed it.

    Any help on this will be appreciated.

    Thanks!
    J. King

  2. #2
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    Disconnect in good shape ?

  3. #3
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,438
    Quote Originally Posted by apprentice3 View Post
    I have a Trane RTAA Chiller tripping on the severe phase imbalance about twice a week. It is tripping out both circuits when this happens. It is usually very early in the morning. Usually compressor A will trip first, and then about 6 min later compressor C trips off. The fact that both are tripping around the same time I assumed that there was a power problem. After checking the voltages i noticed a imbalance, and higher than normal voltages. We called AEP, and they told us that they had a bad voltage regulator on the main lines into the building. After they changed it out the power appeared to be normal. Well the chiller went back down again yesterday. Is there something I can do about this? Everytime this thing goes down the Tracer calls the customer. The tenants in the building are getting upset. What can I do? Is there some other things I can check? I already checked all of the connections, and ohmed out the current transformers. I checked the contacts on the starters, and the compressor terminals. To me since the electric company had the problem before, they may still have a problem, but they claimed that they fixed it.

    Any help on this will be appreciated.

    Thanks!
    make sure that your facility/equipment is not at fault before proceeding.

    i have had this problem before...talk to your customer. ask that they (your customer) get involved with the power company and have the power company speak with you on behalf of THIS POWER PROBLEM ONLY. in regards to this issue, the power company is to inform you as well. ask the power company to send you the power quality report. the issue can be 'Power Factor Correction Capacitors'. the power company adds them to the line to help correct low power factor (not just your customers building but your whole block or area). if 1 or 2 of the PFCC's blow, you can get a pretty good voltage imbalance and it can be random and unexpected.

    if there is a time component (which yours seems to be), there may be a large energy use in your area (manufacturer, etc) that is booting up or starting some large equipment...check in to it. your building may also have some kind of large equipment start up (like the building is starting up or something).
    How to make the perfect "Half-Hitch" knot or any other boyscout knot in 3 easy steps...

    1. Remove your meter leads from the meter and very carefully return them to their storage case or bag.
    2. Wait 2 seconds
    3. Very carefully remove your meter leads from their storage place and enjoy your new knot!

  4. #4
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    No redundancy there ? Just the one RTAA ?

  5. #5
    Join Date
    Apr 2006
    Location
    Columbus, Ohio
    Posts
    809
    Quote Originally Posted by jayguy View Post
    make sure that your facility/equipment is not at fault before proceeding.

    i have had this problem before...talk to your customer. ask that they (your customer) get involved with the power company and have the power company speak with you on behalf of THIS POWER PROBLEM ONLY. in regards to this issue, the power company is to inform you as well. ask the power company to send you the power quality report. the issue can be 'Power Factor Correction Capacitors'. the power company adds them to the line to help correct low power factor (not just your customers building but your whole block or area). if 1 or 2 of the PFCC's blow, you can get a pretty good voltage imbalance and it can be random and unexpected.

    if there is a time component (which yours seems to be), there may be a large energy use in your area (manufacturer, etc) that is booting up or starting some large equipment...check in to it. your building may also have some kind of large equipment start up (like the building is starting up or something).
    thanks! I will start to look into some of this stuff. So will the electric company tell me if there is a large usage around my area at those times?


    I have checked the disconnect, and yes this is the only RTAA chiller on site.
    J. King

  6. #6
    Join Date
    Jun 2010
    Location
    Tampa, FL
    Posts
    101
    I have been advised in the past by tech support to disable phase imbalance protection when there were a lot of nuisance trips. Industrial sites with large motors frequently switching can cause this. They claimed you still had adequate protection from voltage monitoring. You should be cautious and make sure it is not a power problem or a problem with a ct before disabling protection. Good idea to go through the SB electrical checkout proceedures and tighten all electrical conections.

  7. #7
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,438
    Quote Originally Posted by apprentice3 View Post
    thanks! I will start to look into some of this stuff. So will the electric company tell me if there is a large usage around my area at those times?...
    nope. you will need to investigate it yourself. the cool thing is, they will never give you a report that shows anything wrong...so what will happen is that they will fix it, then give you a report.

    what could also happen is a report that is not at the time of day that you are having a problem, so make sure that you specify the time of the day and the day of the week if it is a problem.

    be careful, the report may indicate that the problem lies within your facility...so check your facility first (including your chiller like dp10 said) which is much easier.

    disabling phase imbalance will only move the trip point up from 15% to 30%...so you still have some protection. even if the problem is outside your facility, the power company may not fix it enough so you may be stuck with 30%. a power quality analysis WITHIN your facility may be very beneficial too.
    How to make the perfect "Half-Hitch" knot or any other boyscout knot in 3 easy steps...

    1. Remove your meter leads from the meter and very carefully return them to their storage case or bag.
    2. Wait 2 seconds
    3. Very carefully remove your meter leads from their storage place and enjoy your new knot!

  8. #8
    Join Date
    Sep 2008
    Location
    A land down under
    Posts
    309
    "disabling phase imbalance will only move the trip point up from 15% to 30%...so you still have some protection. even if the problem is outside your facility, the power company may not fix it enough so you may be stuck with 30%. a power quality analysis WITHIN your facility may be very beneficial too"

    The "Severe Phase Unbalance" relates to the 30% unbalance criteria and tells me either the chillers phase unbalance protection is disabled or the condition is occurring when the average three phase current is <80% RLA when the 15% unbalance criteria is not active.


    Have seen many installations where an phase unbalanced lighting load combined with the chiller running with reduced load on a supply with some inherent voltage imbalance have caused this diagnostic.

    The time of day of the diagnostic occurence may be the key to a simple diagnosis or as Jay has indicated may be due to a not so simple to diagnose issue within the facility or the distribution system.

    The attached bulletin is getting on in age but is gold for a simple explanation on he effects of voltage unbalance and compressor load on phase current unbalance (Warning lead rotation is relevant to Centravac, if applied to screws correct phasing must be mantained to prevent compressor reverse phase rotation and catostrophic failure)
    Attached Files Attached Files
    Necessity is the mother of invention

  9. #9
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,438
    [QUOTE=Screwit;13171181...The "Severe Phase Unbalance"...[/QUOTE]

    you're right! missed that in the tag line.
    How to make the perfect "Half-Hitch" knot or any other boyscout knot in 3 easy steps...

    1. Remove your meter leads from the meter and very carefully return them to their storage case or bag.
    2. Wait 2 seconds
    3. Very carefully remove your meter leads from their storage place and enjoy your new knot!

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