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  1. #1
    Join Date
    Dec 2008
    Location
    Live in TN, work in AR
    Posts
    9

    Cottonwood and new chillers

    I am replacing a bank of 6 Carrier 30gt030 chillers in an area that is prone to cotton wood coil fouling. I am considering the 30RAP or the CGAM's. I'm not familiar with microchannel coils used on the 30RAP's or the coils used on the Trane, as far as which would be easier to keep clean from cottonwood. The application is for the remote main switchyard at a steel mill, so there is not condensor water available and installing piping for a remote tower is out of the question as they are located in the middle of a large switchyard. Any info or experience with accesability or cleaning of the coils would be greatly appreciated.

  2. #2
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,725
    I have to say that these coils are much easier to clean with cottonwood on them. All your supposed to use is water and the fear of bending fins are gone.


    BTW I prefer the 30 RAP.
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  3. #3
    Join Date
    Dec 2008
    Location
    Live in TN, work in AR
    Posts
    9
    I have a couple other questions about the chiller layouts. Currently there is a 500 gal tank with a baffle semi dividing it into two parts: a hot well and a coldwell. It has coldwell circulating water/glycol from the hotwell, thru the 6 chillers and back to the coldwell. It has a hotwell pump circulating water/glycol from the coldwell to the process and back to the hotwell. Is this the best way or should each chiller have a hydronic package and utilize its own pump for each chiller.
    Also I need to interface the chillers with wonderware and wanted to do it the easiest way. Currently they are on they're own PLC and do not interface. The new ones will have to. I was told by a controls person that it woukld be easier to interface to the rslogix plc in place and then convert to the tags in it.

  4. #4
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,725
    It's kinda hard to visualize your piping layout here. How many chilled water pumps do you have now? Do you have one pump on a VFD?
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  5. #5
    Join Date
    Oct 2011
    Location
    La.
    Posts
    284
    I would clean with regular water. To get it there you buy a plastic water tank and pipe in a water pump to make your own water source. We used to do this on remote phone switch sites all the time. Just use water though and forgo the chemicals. You will like the ease of cleaning the micro channel coil.

  6. #6
    Join Date
    Aug 2002
    Location
    Greenville SC
    Posts
    436
    No chemicals. Best to use a pressure washer with a fan nozzle. The factory claims you can use up to 900 psi., but I'm not going to find out. Three hundred to three-fifty should work fine. Mush easier to clean the cotton wood out than a regular coil.

  7. #7
    Join Date
    Apr 2010
    Location
    KY,OH,IN
    Posts
    37
    The micro channel coils are nice and easy to clean, very similar to a radiator. If one should go bad they are also easy to replace.

  8. #8
    Join Date
    Sep 2011
    Location
    BAJA AND CALIFORNIA
    Posts
    90
    my experience with micro channel is lot of problem with leaks

  9. #9
    Join Date
    Dec 2008
    Location
    Live in TN, work in AR
    Posts
    9
    Thanks for the comments. The current system is divided into two loops with a tank in common with both loops. The tank also has a baffle in the middle that semi-seperates the water in the tank into a coldwell side and a hotwell side. The baffle only goes up 3/4 of the tank and has a few passages at the bottom to allow the water to flow between the two sides to maintain a ballance of water between them if one loop is circulating more water than the other.
    The loop that goes to the chillers is made up of one pump and one standby pump. It draws water from the hotwell side of the tank forces it trough a header that distributes it into the six chillers and back to the tank into the coldwell side, ready to go to the process loop.
    The Process loop has one pump and a standby pump that draws water from the coldwell side of the tank. It then sends it through a heat exchanger that has the process water on one side and DI water on the other that goes through electrical SCR's. The process loop water coming out of the process loop exits the heat exchanger and then discharges back into the tank on the hotwell side, ready to go back to the chillers.
    Currently all the pumps are controlled by a PLC. Every aspect of the current chillers are also controlled by the same PLC; compressors, fans, low and high pressure switches, everything and interface with Panelview & Wonderware.
    Both the new Carrier and Trane chillers naturally have their own individual chiller controls but can have an individual chiller pump that each individually controls. The pump would draw off a common header that comes from the tanks hotwell. Flow through the chiller into a common header that dumps into the tanks coldwell side. I heard that the plate evaproaters are very sensitive to any type of low flow condition.
    I am wondering which way to go for the chiller loop pumps and how to control. Individual chiller pumps or leave it with a chiller loop pump.
    I will leave the process loop as it is and continue controll by the PLC.

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