In installing a number (8) of air c

[Ramdeom]

In installing a number (8) of air cooled chillers what are the advantages and disadvantages of having a dedicated primary pump for each chiller versus headering the primary pumps so that any primary chilled water pump can serve any chiller? What is the recommended option and why? Are there any particular precautions to be taken with either option?

 

[GT-EGR]

To oversimplify, major reason to have a dedicated pump per chiller is that you elminate any concerns about keeping a proper flow rate through your chillers, since you know all that pump flow goes through chiller. Downside is now you have more pumps to install and maintain. It’s also a simpler control setup when chiller pumps just operate for chiller, and system pumps just operate for system.

Benefit of using system pumps through chillers without dedicated chiller pumps is less pumps to install and deal with, and I believe in the end it’s less operating HP although it’s been a while since I’ve seen this modeled out. You also don’t have to worry about mismatched system and chiller flows. Downside is you need flowmeters and bypasses to make sure you are keeping the flow through any chiller above it’s minimum flowrate or you could damage it.

 

[Ramdeom]

The same number and capacity of pumps are being installed in both systems. When the pumps are headered then any pump can be used with any chiller. If the primary pumps are dedicated to each chiller then if 1 pump is down and a chiller not associated with this pump is also down the 2 chillers will be out of service whereas if they were headered then only 1 chiller would be out of service. This is my thinking.

 

[GT-EGR]

Gotcha, in this scenario, with 8 chillers you have a lot of redundancy. Even in the less than frequent scenario you lose one pump and a different chiller, you still have 6 chillers up and running. So unless you always have peak demand, you are probably still ok.

If you manifold them you get the improved redundancy, but it comes with more complicated controls, less direct flow certainty and probably more automated valving as well which become new failure points. With 3 or 4 or 5 chillers I’d say it’s worth it, but with 8 I’d say probably not.