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  1. #1
    Join Date
    Jun 2012
    Posts
    11

    Trane Chiller MPL alarm

    I have a Trane Chiller CVHF-910 and i have regularly the alarm "Momentary power loss" and i can't find the cause and i would like to know if it's dangerous to disable the MPL fonction in the Field startup group.This chiller has a SSS modele number CVSF0579HA31600K010 type of starter.

    Thank

  2. #2
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,992
    I hesitate to give much advice to someone with such a "slim" profile. Are you an owner or owner rep? Operator? Technician? I would not disable any safety. Several things can cause this diagnostic, some of which could appear to be completely unrelated. My ad vice is call someone familiar with this chiller. Or at the very least, put more info about yourself in your profile. Not trying to be a jerk, just trying to prevent equipment damage or personal injury.

  3. #3
    Join Date
    Jun 2012
    Posts
    11
    I'm the plant chief supervisor of an cooling plant located in north america. We allready worked with a professionnal technician. He check everything he could, but there is no smoking gun of what going on there. At that point we suspect a bad electronic board or the HPC (High pressure control). The MPL can be disable in the software and we both agreed to disable it to find out if not something else is going to show up. We have multiple chiller feed from the same electrical line and none of them have that problem. We agreed that the electric line is good.

    Next time we see our technicien, I'm looking at changing this HPC module as many forum and service bulletin aim at it.

    Thanks all for your support.

  4. #4
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,992
    I believe you're looking in the right direction with the High Pressure Switch. Pay particular attention to cooling tower water temperature. I have seen that result in high enough condenser pressure to open the normally closed contacts in the starter circuit, but not enough to close the normally open contacts that initiate the high pressure diagnostic. Air in the chiller can also raise the pressure to this point. So can a (momentary?) loss of condenser water flow. Or just about anything that will result in abnormally high head pressure. Those that I have mentioned are the most common that I have seen. Good luck.

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,411
    yeygw

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  6. #6
    Join Date
    Jun 2012
    Posts
    11
    Thanks Nuclrchiller, You where right, it was the high pressure swicht that was at fault. A new one has been ordered.

    Thank you very much

  7. #7
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,992
    You're welcome, but are you certain the switch is the problem? It could be responding (correctly) to a high condenser pressure situation. A surge condition at abnormally high pressure can cause the switch to "bump" open the NC contacts, as I mentioned in my last post. In which case the switch would not be the problem, but rather the cause of the high pressure and/or surge.

  8. #8
    Join Date
    Jun 2012
    Posts
    11
    Your're observation are correct. All those conditions could give us the same effect.
    We will track surge, pressure very closely from now that we know that it is not link with the power line or electronic board.

    This situation as start almost 3 years ago and the situation was getting worse each years. From once a week to 2-3 times a day.

    Changing the HPC is not too expensive and will ensure that the contact and setting are as Trane build it and it is important to me to insure the correct operation of this part and not just guessing. Just on what we spend for the technicien, we could have changed it multiple time.

    But it seems that the last few times it trip, the circuit open 3 psi before the factory limit and no surge has been observed. This HPC is the original and have near to 15 years.


    Thank you very much

  9. #9
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,992
    It's possible that the switch has "weakened" over time, however I am concerned about your statement "the circuit open 3 psi before the factory limit...". The switch should open at 15 psig. If the chiller is at 12 psig, that is too high IF it has R123, which I suspect it does. Even for R11 it would be higher than most are designed for. Does it have R123? I hope the technician you are using is experienced on this machine. If you could post a full set of running logs from this chiller it would be very helpful. Including entering and leaving water pressures, from both the evaporator and condenser (using just one pressure gauge, to prevent gauge error). You are correct about the expense of replacing that switch versus multiple visits to diagnose the problem, though.

  10. #10
    Join Date
    Jun 2012
    Posts
    11
    Look like the HPC that I thought was original could have been replaced when they convert this chiller to R123 from R11. That’s a long time ago.

    When I based my 3 psi before factory limit the condenser pressure was around 10 PSIG. The HPC in place is set at 12.5 PSIG. At that point the chiller has trip on MPL and refuse to restart with a phase loss error message. That does convince us that the HPC is at fault and that it does not close the contact for his diagnostic. While we experience this, we were having some surging and we were moving up our set point on the evaporator side. Finally set out at 52 and around 9 psig on the condenser pressure.

    Here are some logs from normal operation, outside temperature below 90 degree Fahrenheit and over just after
    Evaporator pressure, -9 PSIG : -7.5 PSIG
    Evaporator temperature water input: 49 Fahrenheit : 58 Fahrenheit
    Evaporator temperature water output: 40 Fahrenheit : 50 Fahrenheit
    Evaporator pressure water in : 59 PSIG
    Evaporator pressure water out: 51 PSIG
    Condenser pressure, 2.5 PSIG : 8.9 PSIG
    Condenser temperature water input : 81 Fahrenheit : 98 Fahrenheit
    Condenser temperature water output: 90 Fahrenheit : 106 Fahrenheit
    Condenser pressure water in : 44 PSIG
    Condenser pressure water out : 40 PSIG
    Around 2200-2500 GPM on our meter.
    Refrigerant temperature 37 Fahrenheit : 47 Fahrenheit
    Oil temperature 110 Fahrenheit : 118 Fahrenheit
    Vanes position 60 % : 69 %
    Amps 404 : 472

    While running with these condition, the chiller could trip once or twice a day on MPL. That could be cause by a bad contact from the HPC switch. Always restart after a resetting.

  11. #11
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,992
    Let me make sure I'm reading this right; For example, on condenser water temperature input, you have 81 F and 98 F, does that mean a first set of logs (taken when outside temperature was below 90 F) had 81 F and a second set of logs (taken when outside temperature was somewhere above 90 F) had 98 F? And the first set of logs had condenser pressure of 2.5 PSIG and second set of logs had condenser pressure of 8.9 PSIG? If I'm correct on that, you have a problem with the condenser entering water temperature being too high. The chiller is most likely designed for that temperature to not exceed 85 F. I would address this issue first. Your cooling tower appears to have lost efficiency. The chiller may also have low condenser water flow - was one gauge used for both measurements, or were both installed gauges used? Using one gauge, moved back and forth between the two connections, will eliminate the possibility of gauge error, or inaccuracy.

  12. #12
    Join Date
    Jun 2012
    Posts
    11
    Yes yours right, that's how I write the logs, the first row is for temps below 90 and the other is for temperature over 90. From what I see, our system hasn’t been design for outside temperature over 90 and the fact that they have added load over time doesn’t help.

    For the temperature of the condenser water being too high, there is not much I can do for it. I have already tweaked the water flowing troughs our cooling tower to its maximum as well as the air flow. Summer here tend to be hot and humid. When the air is dry, we can see tower water temperature lower than the outside temperature. Today we are seeing humidity in the 80 % and outside temperature in the 90-95 Fahrenheit.

    I can try to get more flow on this particular chiller, I run multiple chiller on the same loop and yes both reading have been taken from the same gauge. This gauge has been installed by our technician.

    Thanks

  13. #13
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,992
    The water temperature that a properly operating cooling tower should supply is based on the dew point or wet bulb temperature. Where are you located? I am in south Alabama (United States) and it is not too uncommon to see temperatures above 100 F with high (oppressive) humidity. Yet I have never seen a properly operating (and correctly sized) cooling tower that is unable to supply 85 F, or cooler, water. I have seen many that were in need of maintenance that were unable to. You mentioned "troughs" in your tower. If it is the type tower I am thinking it is, are there covers over the water on top of the tower? If so, remove the covers to access the distribution pan and its distributors, and clean the debris that is covering them. The distributors will appear to be small holes through which the water "drains". They should have small plastic pieces in them. These are "turbulators" (I think that is the name for them), their purpose is to atomize the water, or break drops into smaller droplets, which increases surface area to improve cooling of the water. I feel compelled to mention that an experienced technician would have already addressed this. Perhaps your's already has, or maybe it is time for a second, on site opinion.

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