Do not have more than one expansion tank location in a system.
Expansion Tank Ation For Chilled Water System Full Or AtThe Closed loop System Should be Pressurized at a Specific Pressure to run Normally, i have makeup water pumps, to initially fill the system and then maintain the Pressure in the System, in case of leaks or drain the pumps should refill the system and pressurize it again automatically ( if Possible ), where should i make the connection for the makeup water in the chilled water system, how do i balance this point, and control it to keep the system full or at a desired pressure at all times, in practical how this can be done, and what controls are required to achieve it Attached Not to scale Sketch for my system, where should be the connection for the expansion tank and makeup water should be The green pipes are related with primary suction and discharge and the Blue with Secondary.Also not sure why you would want to control system pressure with make-up.
The chilled water pumps should be used to maintain the system at normal operating pressure. Make sure your make-up pumps have high enough discharge pressure to push water into the chilled water system. In a closed system, the primary and secondary pumps are purely there to maintain flow by overcoming the frictional pressure losses of the system. As you understand, you should have a make-up water pump and an expansion tank (tank maintains stability in the pressure as the pump cycles onoff). You should locate the make-uppressurization unit at the rooftop level, feeding into the return. The reason for this location is that the make-up pump has to do the least about of work as this point in the system will have the lowest pressure (both static and dynamic). As buildings get taller you need to look closely at the static pressure rating of system components installed at lower levels. The chilled water pumps (23 in total) are used to maintain header pressure (some are on VFDs). ![]() However on tall buildings this can be a high pressure to fill all the way to the top. Expansion vessel and prssurisation pump I agree with others - the return line on the roof is the easiest place and reduces pressure rating of the equipment. In terms of what pressure to maintain - its a balance between making sure the pressure is always positive and creating a high pressure downstream your main circulation pumps at the lowest point. Remember - More details better answers Also: If you get a response its polite to respond to it. Expansion Tank Ation For Chilled Water System Plus About 6The expansion tank must be pressurized to match the static head of the water equal to the highest point of the water piping above the expansion tank plus about 6 feet of water. This is to make sure that all part of the piping is under pressure so any valve open anywhere would not let air in. Connect the makeup at the expansion tank piping connection to the system. In the makeup line put in a pressure regulating valve set to maintain the above expansion tank pressure. ![]() To size the expansion tank you have to calculate the volume of water in the entire system and figure out the water expansion from its lowest temperature to the highest (when chillers off). Look at Amtrol web site to see sample calculation to determine expansion tank acceptance volume required. Because of the expansion tank location at pump suction, static head and use of pressure regulating valve this is the point of no pressure change.
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