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11-23-2005, 07:49 PM #1
I have a maintenance contract for 3 separate floors in an office building. The equipment on each floor is water cooled and there are (2) 25 ton water cooled units on each floor. There are three old Marley cooling towers on the upper roof with a common sump suction line running over to 3 separate outdoor pumps, one for each floor. The return condenser water from each floor goes to its own respective tower. I am responsible for filling and starting up the towers in May and draining and winterizing the towers and pumps in late October of each season.
One tenant moved out and they demolished the old York units and installed (2) two new Typhoon water cooled units. I went to the job today to drain down and winterize that floor. A Nice installation for sure but they installed a 3" flanged 2 way Penn water regulating valve on the condenser return line of each unit. I see a problem here, the pump has the ability to run thru its own timeclock when the a/c units are not calling for cooling. Shouldn't they have installed a 3 way water reg valve instead on the supply line to bypass the water if the compressors are not running? The other 2 floors don't have water reg valves, the condenser water is controlled by a fan aquastats. What will happen to the pump seals if they pump against a dead head? Regardless, should'nt they have installed separate 3 way water regulating valves for each compressor. There are two compressors in each unit. How does compressor #2 know what compreesor #1 is doing to modulate the valve correctly? Sorry for the long post.
11-23-2005, 08:40 PM #2
Not sure about your application, but the systems you describe that I have worked on had a pressure regulated by-pass in the main condenser water lines allowing water to by-pass back to the tower as various units "satisfied". The compressor cycles off, condenser water regulating valve closes due to reduced head pressure. As pressure builds in the condenser water loop the main by-pass begins to bypass back to the tower. If your application does not utilize this function, you may need to look into it further. ALso, if the other systems in the loop are not equipped with water regulating valves, you may not see a dramatic increase in pump head.
11-24-2005, 12:16 AM #3Professional Member
- Join Date
- Oct 2005
Roc, The only time those valves may be needed is during initial startup, before the condenser water has warmed up to 80 degrees or so. Its possible they may be needed if you have a very cold climate.If not currently doing so, control the condenser water temp with fan cycling and the valves will not be needed. I have removed several in the past with good results.
11-26-2005, 01:52 PM #4Regular Guest
- Join Date
- Apr 2003
As far as yor pumps dead heading given enough time they will evenutaly heat up and burn the seals causing leaks.
12-03-2005, 03:17 PM #5Regular Guest
- Join Date
- Aug 2005
if the cooling tower loop is being maintained at a contsant temp. of 80f a water regulating valve is not required. If the tower loops water supply temp varies lower than this especially during low ambient outdoor conditions with no capacity control than a water reg. valve should be used. Water regulating valves are usually installed on the inlet to a water cooled condenser.