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How to size an expansion tank?

7025 Views 7 Replies 7 Participants Last post by  MrEngr
I'm working on designing a central plant. I know I need expansion tanks for my HHW and CHW loops but I need some direction on how to size them.

Any help would be much appreciated.

Thanks,

Brian
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The people you buy your system from should be able to tell you what size expansion tank you need for your system size.
You're in HVAC and dont know how to size an expansion tank. There is an equation for this.
Consult your vendor for appropriate sizing information.

Bell and Gosset has an excellent sizing manual for sizing pressurized expansion tanks with a membrane barrier separator between water and air side.

There are a few things you need to know before you begin sizing:
-total system water content
-average system design water temp
-minimum fill pressure (pressure to overcome height of building +4 to 5 psi)
-max operating pressure of system
-static pressure of system

Methods differ from manufacturer to manufacturer as well as tank configurations. Don't forget to check code requirements.
Is that 4% of GPM. Or of GPH.
Since 4% of 600GPM is 24. And 4% of 36,000GPH is 1440.
4% of circulated volume
Apologies, 4% of fill.
Is that 4% of GPM. Or of GPH.
Since 4% of 600GPM is 24. And 4% of 36,000GPH is 1440.
Here is a link that shows you how to size an expansion tank

Look here, the forum is giving me a problem with posting a URL so you will have to take out the spaces.

www . engineermanual . com/index.php?title=23_21_16.13_Expansion_Tanks
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