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Chiller troubleshooting

Discussion in 'HVAC' started by Pascal, Jul 29, 2021.

  1. Pascal

    Pascal Senior Member

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    they re on freq drives so no surge at start up. They slowly ramp up. And they trip the breaker while running.
  2. rtrafford

    rtrafford Senior Member

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    Ok, throwing this out there, as it's a new issue for me as well.

    One of my units is tripping the same breaker. It will run for a while, but sooner or later it trips. I'm pretty sure it's caused by overheating, relative to the need for servicing the cooling coil. One would think it would trip the high pressure safety, but it's instead tripping the breaker. We're flushing the system well with red line this week, and servicing the strainer beyond merely the basket replacement cycle.

    My tip off? The unit tripping is the top chiller, higher above the water line. I put a heat gun on the discharge point of the coil, and I see a slight increase in temp at this upper unit. I think a good cleaning will resolve. I was told these are very temp sensitive...
  3. Capt Ralph

    Capt Ralph Senior Member

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    Woke up this morning with some thoughts in my head;
    The circulating pump, is it on this breaker?
    The raw pump?
    The pump controller board?
    And condensation dripping down into any Vac connects?
  4. Capt Ralph

    Capt Ralph Senior Member

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    My next thoughts during my first coffee;
    I am assuming that every station (stateroom, galley, saloon) has it's own fan and controller breaker?

    But after running for 30 to 40 minutes, could one of these stations be trying to turn itself or the compressor off?
    A control buss issue?
  5. d_meister

    d_meister Senior Member

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    It may be worth monitoring the voltage supply. Local brownouts can trip breakers.
  6. Pascal

    Pascal Senior Member

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    The Dometic chiller control cabinet is powered by two 63 amp breaker from the main panel.

    1 breaker powers chiller 1 & 2, the other powers chiller 3, the circulation pump and the sea water pumps (two installed with a selector switch. It s the breaker to chiller 1 & 2 that trips.

    Inside the control cabinet, each pump and chiller has its own breaker. Problem is that the individual chiller breakers are 40 amps each. So... if for some reason each chiller pulls 38 amp and the other one 30, the main panel breaker will trip.

    shores power goes thru an Atlas system which keeps voltage and freq spot on. Plus the boat monitoring system would alert me if voltage had dipped

    with chillers the air handlers (on their owner breakers) do not control and are not linked to the chillers and compressors. The loop temp is monitored by the chillers control which activates them as needed to keep the loop at the set temp
  7. Donzi 54

    Donzi 54 Member

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    Are you sure that it is not tripping when one of them restarting? They normally don't run full time. At least not here in New Jersey.
  8. Pascal

    Pascal Senior Member

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    lol welcome to south Florida and our currently 92 deg sea water vs 71 in NJ :)

    again, these have frequency drives and ramp up slowly. No surge at all. And no the tripping occurs while running.
  9. mapism

    mapism Senior Member

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    You must be tired of writing that. :D
  10. Capt J

    Capt J Senior Member

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    It's also possible to have a frequency drive going bad. I've had that happen before.
  11. Donzi 54

    Donzi 54 Member

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    I agree, I've seen it also. Although on other systems that used them.
  12. Pascal

    Pascal Senior Member

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    true. We ve replaced both on the 84 over the years, and an ER blower drive as well. But the failure was obvious. Just not turning on, no display. Never tripped a breaker. Anything is possible though
  13. mapism

    mapism Senior Member

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    Did the same happen after running 1 & 3, eventually?
    I mean, did the common 1+2 breaker stays on with 1+3 running, and did it trip shortly after turning 2 on again?
    If so, I think the option of replacing the single 40A breakers with 30A ones is the easiest way to check if either 1 or 2 is the culprit.
    Besides, if either the 1 or the 2 30A breaker should occasionally trip in turn (rather than always the same), THAT could suggest a VFD defect of some sort.
  14. Pascal

    Pascal Senior Member

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    Nr 1 and nr 2 will run forever separately. If both are on, their common breaker trip.

    Yesterday I ran them using a clamp on fluke with the max function activated. It never recorded a spike whether when monitoring either chiller or the combined feed. Doing more testing today

    both chillers combined run at 55/56 amp on the clamp meter which may be a bit close to the 63 amp breaker. According to the cruisair diagram they should pull 23 each.

    going to revisit the raw flow to see if we can lower the temps therefore the amps. Thru hull is clear, strainer is clean, I switched to the second pump. No difference. I m wondering if the pumps aren’t tired with eroded impellers.
  15. Capt J

    Capt J Senior Member

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    Are you on generator or shorepower? In the U.S. or Bahamas? I'm thinking it might be a seperate issue entirely. You have an occasional voltage drop, volts drop, amps go up, breakers trip on Chillers 1+2 and generator (or shore) voltage comes back up and you never notice the voltage drop that caused the chillers to use more amps and trip the breaker.
    d_meister likes this.
  16. Pascal

    Pascal Senior Member

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    We re here in Miami. Happens both on shore and gen

    if there was a voltage drop for some reason the Isis would throw an alarm. Our shore power goes theu an Atlas System so it s supposed to be pretty stable. I was in the ER when the breaker tripped; nothing obvious like voltage dip, sound, etc.

    Right now it’s been holding for a few hours. The clamp on shows consistent amperage on chiller 2 at 26/27 amps which is a bit higher than it should be

    next step is going to be to pull the back up raw water pump and check the impeller for erosion. Age unknown. Coils are hot despite recent descale, they’re around 95 at the bottom and 120 at the top.
  17. Capt J

    Capt J Senior Member

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    Higher chiller temps, will cause higher head pressure, and higher amps. I usually see 10-15F above ambient water temp on clean chillers.
  18. dennismc

    dennismc Senior Member

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    No expert here but are breakers not actually rated at 80 % on full running load, if so a 60a brkr would overload at 48 amps, if tripping often then they will also weaken and trip earlier. If this is incorrect accept my apology for posting.
  19. Pascal

    Pascal Senior Member

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    I m not sure if it s 80% but ideally yes you want some margin. Problem in this case is that this type of euro breaker tops at 63amp. Getting a higher rating would require panel surgery.

    J, water temp is about 90 right now... top of the coils wheee water exits are around 115. The more I look at it the more I think it s a flow issue.
  20. rtrafford

    rtrafford Senior Member

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    Ok, so after a thorough Red Line cleaning of strainer, pumps, and coils...I see lower discharge temps with the heat gun, lower amps on each leg of the AC draw, and no more tripping of the breaker for the upper chiller. So, again, is it possible that your coils are getting fouled and causing that amperage increase to trigger your breaker? Mine did.