If you are about to perform a test and balance on a Chilled Water Closed Loop system, my advice, don’t start it without knowing the piping system is full of water and free of air, unless you don’t mind wasting time. Go to the roof, open some vents, if you don’t get water, without air, then begin. If you get either, notify the MC to get it ready!!!
Chilled Water loops are primarily a Closed Water Loop. There is an exception, rarely seen anymore, and that is when an open tank (with a float valve inside maintaining a water level) and positioned above the piping system, connected with a pipe, (typically a 3/4″), to keep the piping system full. And you only need about 20 PSI of domestic water pressure to get the job done.
Although no one seems to like them anymore, they did the job, as it met the parameters needed for the piping system. Keep it full of water!
Well now, we could have the make up water in a chiller plant on the second floor, with a building above, (for this example we will use 20 stories of an office building, and consider each story is 12-foot slab to slab).
Okay, now this make-up water system needs to have the water pressure needed, and would need a PRV (Pressure Regulating Valve).
Well, it needs more devices, such as a gauge or two, valves, a blow-off, perhaps with a by-pass for fast make up, and definitely should be connected to the “SUCTION SIDE OF THE PUMPING SYSTEM”. This is a must!