Chiller Compressor A and B

[tower2]

I'm having a problem with the compressors shutting down on the digital readout of the chiller. I'm getting a reading at different times "Phase reversal, Phase unbalance, and overload protection." The B compressor will be running then it will shut down due the readout on the panel "Phase reversal". I then try to switch over to compressor A and it will try to turn on, but then it will kick out on "overload protection". It seems that on a warm and more humid days, we encounter these problems more frequently. This scenario has been going on now for two summers.

Our area is a heavy construction area and every now and then we will experience a brown out. We've contacted our power and lighting company and they claim that they are within the range without causing damage to our equipment.

We've had profesional machanical service people come to our site numerous times and to me they are having a difficult time getting to the bottom of this problem. According to them, they checked every aspect of this chiller unit for it to run in it's normal condition. One thing I've noticed that when the service tech was putting one lead of the voltmeter to the one leg of the contactor, going to the compressor, and the other lead going a metal surface his reading was going to ground. I addressed this to him as a problem and he didn't seemed concerned.

Question I have is, are the compressors failing? Do I have a current/voltage imbalance somewhere that is causing a phase imbalance? Also from the main distribution panel to the breaker panel of the chiller we are about 200' apart. Could there be a severe voltage drop when we are experiencing a brown out?

I appreciate any info concerning this ongoing problem I've been having. Thanks

 

[rbulsara]

You need some good electrical engineer at the site to look in to the matter.

Beyond that post some more details such as rating of the chiller, motor HP, rated voltage current vs. actual readings at the time of incidents.

Type of starter. Size of Upstream transformer. How old is the installation. How frequent is the problem? be more specific.

Set points and tolerance windows for UV, OV, OL etc..

Sounds like besides being tight settings, your utiltiy supply is weak or fluctuatig. Do you have a stand by generator of adequate size? If so see what happens when on generator. You may want to install some power quality monitorin equipment over sevaral weeks with proper trigger points set for waveform capture.

 

[jraef]

rbulsara is right, you need to provide more info for us to offer some meaningful advice.

But I can offer some anecdotal info that may help. I have some well pump installations where there is a lot of residential housing going in and construction going on. In these hot summer months we get a lot of Phase Imbalance trips. We have determined that since the residential and construction loads are connected at random, the utility is unable to adequately predict the balancing of the power draw among the 3 phases on that substation. When we would arrive the next morning to check out a trip, everything looked great. If we checked it again right after lunch when all the AC units and contractor's power saws were running, we had upwards of a 30% voltage imbalance! At 7:00PM, everything went back to normal as the contractors went home and fog rolled in so the AC units could shut down.

"Venditori de oleum-vipera non vigere excordis populi"

 

[blutfort]

You should be able to rent a power monitor that samples the incoming power every so many seconds and records it to Flash Ram. In addition it will log an event / alarm if power quality falls outside of specific tolerances.

If you didn't want to go this route, for less than $100.00 you can by a three phase monitor relay from a company called Kele Associates. Then hook up a latch circuit and see if it ever trips. The permissive tolerance is adjustable via a pot on the side of the relay. If your chiller keeps tripping and this relay doesn't you could have a bad control board.

You could keep tightening the tolerances on the relay until it trips with the wind blows if you wante to, that way you know it wasn't a sensitivity issue. I'd opt to rent the data logger however.

 

[busbar]

 
Aside from monitoring/logging electrical operation of the chiller with portable instruments, there may also be need to test the electrical response and protective functions of the ‘digital readout’/control module.

Depending on the accumulated aggravation level and troubleshooting effort expended—as is done with multifunction motor/generator-protection relays—specific analog {precise multiple AC current/voltage} quantites {with a ‘relay test set’} may be injected into the relay to determine if it is responding “as advertised.” [It is hard to imagine that the device is detecting a true phase reversal on otherwise functional equipment.] A problem may be that the module is proprietary, lacking published information to adequantely test, but too expensive to casually do a wholesale swapout.

 

[mc5w]

Some of the solid state phase rotation relays can also give a false phase reversal signal under some unbalanced voltage conditions.

You might have to change over to the old style phase rotation relays that use the 3 phase torque motor principle. These use a solid aluminum disk rotor just like a kilowatthour meter. The rotor actuates a small switch if phase rotation is correct and another for phase reversal.

Mike cole, mc5w@earthlink.net