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  1. #1
    Join Date
    Jan 2007
    Posts
    8

    Question Glycol chilled water loop question

    We are going to use prop. glycol in our c/w loop for the first time this year. We have a 2100 gal system in a 5 story building. We installed an automatic glycol feed tank and introduced enough PG to make a 30% concentration. My question is that we seem to be losing pressure in the system and there doesn't appear to be any leaks in the system. We are trying to maintain 65 PSI in the system with the circ pumps off. We isolated the expansion tank in an effort to rule that out, no luck. We isolated the glycol tank to eliminate that possibility, again no luck. We checked every air handler and found nothing. All air vents are valved off. No shaft seal leaks at circ pumps. We've pretty much eliminated the obvious causes. Is there some type of dynamics related to a glycol loop that we are not aware of?? Any information would be most appreciated. Thanks in advance, Gene
    Last edited by wccfgene; 01-25-2007 at 07:33 PM. Reason: Omitted additional information

  2. #2
    Join Date
    Jan 2006
    Posts
    530
    you won't have the same pump capacity if you go from straight c/w to p.g @30%.

  3. #3
    Join Date
    Jan 2007
    Posts
    8

    Post

    Quote Originally Posted by cold in alberta View Post
    you won't have the same pump capacity if you go from straight c/w to p.g @30%.
    We aren't running pumps at this time, we've filled the loop and are just trying to get it to maintain pressure. I guess my question is if the system is tight and flooded, is there another reason why am I dropping pressure and taking on more glycol? We must be missing something. Thanks, Gene

  4. #4
    Join Date
    Dec 2004
    Location
    Mid-west
    Posts
    567
    I've never seen a problem like that and we have many glycol systems in operation, in most we disconnect any water feed to the system after we've filled and pressurized the system so we won't dilute or flood a space with glycol if we have a leak and still don't lose pressure.

  5. #5
    Join Date
    Jun 2001
    Posts
    160
    Did you drain the loop before adding the glycol? If you introduced air to the system your air scoop may continue to remove air for a while. How long have you been losing pressure? 1 week? 3 weeks?

  6. #6
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,254
    are you leaking out through the high pressure relief? i have one building where the relief is piped right into the drain. it is really hard to tell if it is leaking. 65# seems a little high to me, why so high? where are you trying to maintain the 65 psig? in the basement or in the penthouse? double check that pressure relief.
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

  7. #7
    Join Date
    May 2004
    Location
    Boston
    Posts
    72
    any under gound lines to a tower or chiller? If you have time you can see were pressure stop dropping and figure out height by pressure left in system and narrow your leak down to an area, Glycol seems to find leaks that are there befor but never leaked until now

  8. #8
    Join Date
    Aug 2006
    Location
    Milwaukee Wisconsin
    Posts
    41
    Is your system outside, if so Glycol reacts to outside temp changes especially if your below freezing. I have a solar system that looses presure when ambients change. Or, if you added glycol to a system with water you might have to mix up system.




    Keep it basic!

  9. #9
    Join Date
    Jan 2007
    Posts
    8
    Thanks for the suggestions. My chiller is in the basement of the building. My HVAC tech tells me we need 65 PSI to get adequate flow up to the 4th floor. Seems high to me also, all of my other buildings run 35 PSI or thereabouts in chilled water loops. We may have to re-think this. I had thought of outside air dampers on any number of AHU's opening up to maintain a mixed air temp might be the culprit. O/A dampers open, glycol loop drops pressure & glycol feed tank pushes more into the system to make up the difference in pressure.
    We have all new mechanical equipment in this bldg, chillers, boilers, AHU's,
    glycol feed system, etc. so we're going through a bit of a learning curve. Thanks again, Gene

  10. #10
    Join Date
    Aug 2005
    Posts
    831
    2 feet per pound, plus or minus. 12 ft per floor x 5 equals 30#. 40# ought to be adequate. check rating of relief valve. Hydrostatic pressure works in reverse. Start with 80 degree water without expansion room and start cooling it, you will lose pressure. isolating X-tanks would cause that, they may be logged to begin with. No heat involved?
    eventu rerum stolidi didicere magistro

  11. #11
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790

    help me out here

    12 ft per floor x 5 equals 30#. ?????
    It's great to be alive and pumping oxygen!

  12. #12
    Quote Originally Posted by The Doctor View Post
    12 ft per floor x 5 equals 30#. ?????
    2 feet per pound, so 12x5=60 feet devide by 2 equals 30.

  13. #13
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790
    got it
    It's great to be alive and pumping oxygen!

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