Page 2 of 2 FirstFirst 12
Results 14 to 17 of 17

Thread: To hot to run!

  1. #14
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    866

    What's the design

    Mike Robinson- I have had situation at several plants in the Houston area. As they all use 100% outside air for the labs. I would suggest looking at the original design criteria. Unfortunately ASHRAE is still using 95*F as the design temperature in Houston. Unfortunately again when the outside air temperature rises to 100*F you are 6% over design, at 104*F you are 12% above design I had one that the Trane start-up mechanic through his hands up at the start-up as he could not keep it running in the heat. It was a 200 ton RTAA and it wouldn't even try to load with out shutting down. What I had to do was 1) to get it running was jump out the flow switch and reduce flow rates as it is hard to produce 44* water when you have 90* water entering. I adjusted the flow to maintain a 10* delta "T" and as the return water cooled down I would open the valves alittle at a time. 2) We installed a by-pass secondary loop with a 3-way valve preset to only allow the minimum flow rate from a design flow of 500 GPM, to 220 GPM, just enough to make the flow switch contacts, which is the minimum flow allowed for this evaporator and as the return chill water dropped a little it would start to close off by-pass mode and allow more water flow through the chiller. When I had the flow switch jumped out I was always there, at the customers and Trane's expense as this was a combination of the plant engineers and Trane's engineers fault. Until the firm I was working for had installed all the necessary controls to achieve our permanent solution-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  2. #15
    Join Date
    Aug 2008
    Posts
    322
    Quote Originally Posted by ga1279 View Post
    Mike Robinson- I have had situation at several plants in the Houston area. As they all use 100% outside air for the labs. I would suggest looking at the original design criteria. Unfortunately ASHRAE is still using 95*F as the design temperature in Houston. Unfortunately again when the outside air temperature rises to 100*F you are 6% over design, at 104*F you are 12% above design I had one that the Trane start-up mechanic through his hands up at the start-up as he could not keep it running in the heat. It was a 200 ton RTAA and it wouldn't even try to load with out shutting down. What I had to do was 1) to get it running was jump out the flow switch and reduce flow rates as it is hard to produce 44* water when you have 90* water entering. I adjusted the flow to maintain a 10* delta "T" and as the return water cooled down I would open the valves alittle at a time. 2) We installed a by-pass secondary loop with a 3-way valve preset to only allow the minimum flow rate from a design flow of 500 GPM, to 220 GPM, just enough to make the flow switch contacts, which is the minimum flow allowed for this evaporator and as the return chill water dropped a little it would start to close off by-pass mode and allow more water flow through the chiller. When I had the flow switch jumped out I was always there, at the customers and Trane's expense as this was a combination of the plant engineers and Trane's engineers fault. Until the firm I was working for had installed all the necessary controls to achieve our permanent solution-GEO
    Update Well I went back on saturday took power washer and washed front side of the condenser then I pulled all the fan guards and power washed the coils from the other side. Boy did I see alot of dirt come out by looking at it you would think it was clean but it wasn't. I sarted chiller up sunday about noon it has been on line ever since. It holds 45* water untill about noon then creeps up to about 51 not to bad for these hot days the oil temp on a is 161 and on b is 156 all is well right now. Thanks for all the info everybody maybe I can repay it some day.

  3. #16
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,579
    Quote Originally Posted by mike robinson View Post
    Update Well I went back on saturday took power washer and washed front side of the condenser then I pulled all the fan guards and power washed the coils from the other side. Boy did I see alot of dirt come out by looking at it you would think it was clean but it wasn't. I sarted chiller up sunday about noon it has been on line ever since. It holds 45* water untill about noon then creeps up to about 51 not to bad for these hot days the oil temp on a is 161 and on b is 156 all is well right now. Thanks for all the info everybody maybe I can repay it some day.
    there you have it, nobody believs me about these coils, even in our office. I just talked to 5 techs this morning with similar issues, all won't clean the coils, I just tell them they are 4'' thick, a water hose won't cut it. let alone on a chiller with sub par service in the past.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  4. #17
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    866

    I'm glad for you MR.

    Mike Robinson- Glad to hear it all worked out for you, if you do reduce your flow a bit you can also loose your late afternoon problem. Lower GPM higher delta "T" . In my case though this was a brand new unit, fresh from the retired bikers factory in Pueblo, CO. It obviously needed another 100 tons during the summer heat. No engineer from the plant or the Trane office would admit the unit was undersized. So, we used some tactics that were above and beyond. The Trane tech who tried to do the original start-up asked the magic question. Who's crazy design idea was this? I got to tell him the name of the Trane sales engineer, priceless.-Geo
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

Page 2 of 2 FirstFirst 12

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event