Decoupled Lines in Chilled Water Systems

The typical application I have ran into is a chiller loop that is primary and runs a constant flow through the barrels and those chillers have dedicated pumps to maintain the design flow through the chillers. The other loop is what I would refer to as the house loop or the secondary loop and that loop will also have dedicated pumps, these days many are on VFD'S (Variable Frequency Drives) Pumps throttle based on the connected load demand.

The de-coupler is the piping connecting the primary to to the secondary and is usually set by a critical distance or so many pipe diameters apart. Do a search on Primary and Secondary Hydronic Applications and you can see a diagram better describing my garbled explanation.

I just pipe them, I don't design them.

Pipeit:

To add to what was said, there is the primary pump and loop, which circulates water through the chiller at a constant speed. Then there is the secondary loop to the building, which has it's own pump, and typically VFD. They share a common pipe, or decoupler pipe, which basically connects between the supply and return of these two loops. As the secondary loop pump increases speed and requires cold water, it will pull the cold water out of the primary loop. As it pulls more and more water out of the primary loop, the flow through the decoupler pipe is less and less. It will reach a point where the building return is equal to the primary pump GPM, and there will be no flow in the decoupler pipe. So in essence, there will be no circulation, but all return water going into the chiller. In fact, the decoupler pipe can actually flow backwards, depending on the GPM of each pump and the mixing of bulding return with chiller supply. That description was only one chiller. Make contact with your local pump representative and schedule a lunch and learn with some diagrams. This stuff is too complicated for one paragraph. Best regards.

hi Dude,

If you have any drawings with this system of chilled water you are talking about can you send me please on mdzakeers@gmail.com.

I am planning to design a such system but would like to know the system concept first before i design.

Thanks in advance