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Thread: Trane RTCA 500

  1. #1
    Join Date
    Dec 2009
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    Hotlanta GA.
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    Trane RTCA 500

    Well it looks like I need to get up on these monsters. got 6 for now, with 5 more due in by years end.

    First question one or concern is understanding the oil system, now I knwo were it goes and theres no pump, my obsevation is the oil temperature while running. I have one machine that is showing higher temp then the rest, normally around 30 degs. and at times the oil temp is higher then the dich. presure of say 185, or I'll see a HP of 230 with oil at 190 dg. Runnign 134a in these units.....

    coils look fairly clean, doing chw. set point @48 deg. machine is fairly loaded, say 85% at times 95%.

    Question - I read this sequence of operation were the if oil reaches 170+ deg. the female valve is activated or deactivated, ( I need to refresh my reading on this) and this will allow the machine to cool the oil before reaching the 200 cut out limit. New to me, so am looking for an exsplination on this, the units DO NOT have oil coolers on them. Am I understading the machine is unloading to cool the oil ???? If so, how ???

    As I said, I need to get up on these machines, as I over see them now, I'm more of a centrifigle chiller mech...... Screws are a bit new to me.......need to get it in my head NO OIL PUMP !!!!

    Thanks................

  2. #2
    Join Date
    Mar 2004
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    ottawa canada
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    First off its an RTAC
    Second ...never mind the oil temp
    Third.....holy crap 230psi head !!!!!!!134a whats your condenser air inlet temp !!!! Are you sure the coils are really clean fans all working and running the right way ???????
    Do all the units sit side by side and are you getting air recirculation off the condenser .
    Are the units surronded by a wall etc ???
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    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 .

  3. #3
    Join Date
    Jul 2007
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    The Hot South
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    I'm assuming your talking about an RTAC.
    The female step load valve is energized (loaded) when the oil temp gets too high. This lowers the discharge superheat. The oil temp is the same as the hot gas temp. If your running 230 PSIG with 190 deg oil (discharge gas) temp, that's 50 deg discharge superheat which is pretty high if the compressor is loaded up. First, you need to check the sensor, then make sure all fans are running (and in the right direction), you also need to check the charge and make sure the EXV is maintaining 0" liquid level and not running over 70% EXV position at full load.

  4. #4
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    It's normal for these units to run head pressure that high down here in the South with the 100 deg days we've been having. I see it all the time in Texas.

  5. #5
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    Mixing oil and fire with a big spoon.
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    are you sure that it is a 500 ton unit? i don't see anything bigger than a 250 available...at least in an RTCA (which is an air cooled remote condenser for an RTUD)...unless you are talking about an RTAC.

    if it is an RTAC, then things are quite a bit different.
    "Mother" is the name for God on the lips and hearts of children....The Crow

  6. #6
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    500 ton is the largest RTAC Trane makes. We have several. They're monsters with 28 fans.

  7. #7
    Join Date
    May 2000
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    Houston, TX, USA
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    I would check your split on your coils. Either looking for dirty coils or air recirculating. Its been very dry here in TX and have been seeing a lot of condensers getting plugged coils causing them to run higher than normal pressures. Don't go by visual on coils, go by splits. And those high pressures are not normal unless you have dirty coils or air recirculation. I am in Houston and I have seen those pressures with dirty coils. Note: they did not look too dirty but then checked split=35-40deg. If so then you need to wash.
    We have a customer that we have been going back every month to wash coils due to getting plugged from dusty conditions (caused by very dry weather).

  8. #8
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
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    OK, yes its a RTAC 500, need to put my glasses on for the important stuff.

    We here in HOTLANTA will see 98 with 89% humidity, thats hot and muggy............. deal with it.........

    The machines are spaced 10 feet between each at set of three each, so two sets of three, the three are seperated 10 feet, the sets are over 100 feet between. all are sitting on pads on the ground. no reall wall toubles. Today you could walk down between the two running side by side and see 110 air being sucked in........ Yep there may be a recirculation problem !!!!

    We are getting swap coolers put on to help in the summer time, it amounts to filter media on the sides so all air is drawn throug the media, then its sprayed with mist, treated water to give the swappp cooler affect, two doen so far, just can't run them right now due to construction dust. Fact: water and dirt make MUD, filter media adn MUD don;t mix...........

    Now for oil temp, not to worry ???? Well thats not so easy, see wne it hits 200 the unit will shut down on high oil temp = NOT GOOD !!!

    I see so far, must maintain a cleen cond coil, or at least close to clean...........
    All fans must be ready to run.......... there is option for phase monitors for cond. fans power supply, well, when y adrop too low those things lock out the fans, drop one relay and ya loose 6 fans........... MORE NOT GOOD !!!! SO we had to adjust them lower for out HOTLANTA power swings this week............ wonlt knwo ya have the trouble till the unit starts going out on high head........... good thinking Trane........... make the unti trip on head instead of fan troubles..........

    I need to read more and se more on this femake loading unloading thing...... Need to have a better picture for myself before I feel good about it. SO will take in your info and ponder on it and see if I can clear things up for myself.........

    By the way, whats the normall subcooling at 100% load on a two compresssor circuit ??? I heard 15 deg. reading the liquid line going to the filter dyer before the exv.

    Well always a pleasure ya'll, keep me goin !!!

    Thank you to all so the help and info...............

  9. #9
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    These units do not come with a phase monitor that drops out the condenser fans. That must have been field installed. Are these chillers at the HP data center by any chance?

  10. #10
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    pm me

  11. #11
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    The oil temp will come down if you can get the head down . the oil cooler is in the top passes of the condenser coil and must be spotless clean not just look clean .
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    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 .

  12. #12
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
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    As an "Atmospheric Environmental Control Specialist", I understand the need for clean coils, these RTAC look to be pretty picky !!!
    I will look at the coils tomarrow, need to verify the oil cooler you speak of. All part of getting to knwo the machine.............

    Thanks...........

  13. #13
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    The RTAC doesn't have an oil cooler in the top of the condenser. The RTAA does. You can get an oil cooler option that uses a TXV and brazed heat exchanger.

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