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    Trane chiller issues (16 Posts)

  • Timco Timco @ 4:25 PM
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    Trane chiller issues

    Hello all!

    So at the end of last season, I got my refrigeration license and started reading everything I could find. I feel like I am pretty good with residential AC but one of my accounts has a Trane 40 ton chiller with a cooling tower. After going through the entire unit, I found that under full load, it has some issues. The superheat is fine, but the subcooling was way off and there were bubbles in the sight glass. It took 15lbs of R-22 to get the sight glass clear, but the subcooling is still way off and throttling back on the building flow only does so much. I am also still under on the suction pressure but am over with the discharge pressure at full load. The numbers are much better with half of the compressor unloaded.

    Am I going to see the subcooling drop out to somewhere close to normal (12-15*) as I approach the correct suction pressure for the condensor water temp and the outgoing water temp I am running? Oil level is fine, pulls right at the max amps under full load. I am a bit worried about having to add over 15lbs of refrigerant to a running system.

    Thanks in advance for discussing a newbie topic.

    Tim
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
  • Techman Techman @ 6:29 PM
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    Chillers are cool

    Specifics are needed here,I think.PSIG's,temps-both freon and water. Curious though,what is the chiller chilling? AC? Production line ? How many lb.s of r22 does the system/reciever hold ?What type of chiller heat exchanger?Sight glass or moisture indicator?Good Luck to you in your new field of work.!
  • Timco Timco @ 7:58 PM
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    Specifics

    Cooling tower water out is 90*, in was like 75-80*. It did not reach 80* here today. Cooling tower working very well, great flow and new nozzles. Hydro-air system for 45 apartments. Cold generator, water-cooled, condensing, 40 ton. The suction line was 47* and the P/T chart gave me 35* as my calculated temp based on the pressure. There does not seem to be a moisture indicator, just a clear sight glass. I will have to pull up the manual on this chiller and give you the R-22 total capacity. The building water was 43* out (setpoint) and maybe 47* back, (low delta T) but it was not a very hot day. On a chill call, it runs at half-unloaded because there is very little difference in the water temps. The liquid line temp hovered around 80-90* depending on if half of the compressor was unloaded due to being close to setpoint. Filling 15lbs got rid of the bubbles in the sight glass but just started to drop the liquid line temp. I left the superheat set based on the half-unloaded load and jumped the unloader out to stay on half output because of mild conditions and the reluctance to add more refrigerant.

    I would love to learn this.  Thanks for the help.

    Tim
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
  • Ironman Ironman @ 9:32 PM
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    Dirty Condenser?

    It sounds like your condenser may need de-scaling or perhaps the strainer is clogged. 10 - 15* delta T under part load and a mild day is too high.
    Bob Boan



    You can choose to do what you want, but you cannot choose the consequences.
  • Timco Timco @ 9:54 PM
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    scale / condenser

    So last year I did a de-scale and the solution came out pretty clean. I used a de-scaling solution from Johnstone supply. As for the strainer, is that the large canister in line with the liquid line? I assume I have to recover, fix, evacuate, and recharge to clean the strainer and not just pump down and close the discharge service valve? Should I charge to the correct suction pressure under full load first and see if I get decent results before going through the entire recover / evac / charge process?

    The 10-15* delta T is on the cooling tower loop. The building loop is very tight. maybe 5*.

    I really appreciate the thoughts on this. It will mean a lot to my customer to have this flying.
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
    This post was edited by an admin on June 20, 2011 9:55 PM.
  • Ironman Ironman @ 10:10 PM
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    Strainer

    No, I was referring to a strainer in your condenser water line. It looks like your not transferring heat efficiently from the condenser to the water. A high delta T would indicate insufficient water flow through the condenser.
    Bob Boan



    You can choose to do what you want, but you cannot choose the consequences.
  • Timco Timco @ 10:30 PM
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    strainer

    When I fired the unit up 2 weeks ago I cleaned that, but can easily check that again. It pops right out. At start-up, the outlet to the tower is pretty hot, and the water coming back is much cooler. As the chiller takes the building water down, it equalizes pretty fast. The temp to and from the tower were pretty close when I left. excellent pressure at the tower nozzles.

    The only strainer I am aware of is in the tower.
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
  • Techman Techman @ 7:22 AM
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    Timco.

    Good morning! Is that canister in the liquid line the filter/drier ? It is very imporant to pump down that freon out of the liquid line/canister before changing the f/d  where ever it is .What were the pressurers? Something else to read about is Legionellia Disease and Towers. It's amazing!Got a model #  ?,I'll get a manual and read it.Why close the discharge valve ? There is no King valve ?
    This post was edited by an admin on June 21, 2011 7:34 AM.
  • Timco Timco @ 8:19 AM
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    pressures

    The suction started off at about 65psi but after running for an hour was down at 50. At 90* condenser water, and 42* chilled water temps, I should have 61.1psi. Bubbles in the sight glass. (half empty under full load, just bubbles half unloaded) I brought it back up to 56psi with 15lbs of R-22, full load conditions.

    Discharge was 220psi or so, and I should have 204.7 based on the above conditions.

    Says liquid capacity of the evap is 27.2 but I think that is the water, not the refrigerant. Does not specify in the manual.

    I only considered closing the discharge service valve when cleaning or servicing the filter / drier to be safe but have not done this as I did not know if I needed a complete evacuation prior to servicing the filter / drier. No 'king valve' noticed.

    On the tower, I run an anti-scaling solution but not sure if that would do anything for the leigonellia. Tower is fairly new, but has run great so no homework or manual on that part.

    Thank you!

    Tim
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
  • Techman Techman @ 6:54 PM
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    How's that chiller?

    Has the comp been operating fully loaded w/ a fully loaded system?
  • Timco Timco @ 7:11 PM
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    full load

    Was blowing fuses, 100A. Was kicking off on overloads. Seems to be running much better since I charged with R-22 and fixed the spray nozzles in the tower, but kicked off today, I am back down there tomorrow.

    I have 5 gallons of 'condenser / tower de-scaleing additive that I will be adding 1:15 and it claims to de-scale even heavily scaled condensers in hydronic open & closed systems with no down time.

    I am also bringing my refrigerant pump to get the rest of the can of R-22 in there if needed.

    Any last minute things to check would be appreciated. I have checked the anti-recycle timer and the 2-stage t-stat and other components, and all are working well.
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
  • Techman Techman @ 10:18 PM
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    OK

    hi &lo press,superheat/subcooling/bldg supply/return temps,tower supply/return,comp amps/volts,ambient temp,and while you are there the water pump's inlet/outlet press and motor amps and pump's mfg/mn.#
  • Timco Timco @ 10:29 PM
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    Info

    OK. I won't be able to get the tower recirc pump's pressures because there are no tappings out there. I had it rebuilt last year due to leaking seals.

    The hard part will be getting it up & running. Under full load, it is tripping out and will restart if manually reset and the anti-recycle timer times out 5 minutes.
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
  • Tom Blackwell Tom Blackwell @ 10:12 AM
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    Subcooling

    Be careful with taking too much stock in liquid subcooling readings. Water cooled equipment has limited capacity for subcooling the liquid, because the amount of subcooling can never exceed the condenser approach temperature. Water cooled equipment will normally operate between 5 and 10 degrees approach on the condenser at full load; even less at part load. Charging should clear up the sight glass plus a few pounds for a chiller of this size. Your numbers point to an overcharge. Head pressure should be the saturation pressure of the leaving cooling water, plus a little for approach.
  • don don @ 4:25 PM
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    In agreement with Mr blackwell

    I hate when i have a chiller with hydro unit in a apartment building.many times not enough load on the loop due to clogged air filter,dirty coils,,blocked return.Indoor fans not running.closed register.
    The fact that your saturated temps are dropping even at part load seen to point me in the direction of the above mention possibilities
  • Timco Timco @ 11:55 PM
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    dead

    Discoloration of the oil. Very high suction pressure. Valve rattle. Compressor shuts down on thermal overload even when run on half-load. No cooling capacity. Blows 150A fuses.

    Pronounced dead at about 8:00 PM my time.
    Working on steam and hot-water systems isn't rocket science....it's actually much harder.
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