How to size an expansion tank?

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.

4% of circulated volume

bm4branes said:

4% of circulated volume

Click to expand...

Is that 4% of GPM. Or of GPH.
Since 4% of 600GPM is 24. And 4% of 36,000GPH is 1440.

beenthere said:

Is that 4% of GPM. Or of GPH.
Since 4% of 600GPM is 24. And 4% of 36,000GPH is 1440.

Click to expand...

Apologies, 4% of fill.

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