valve flow capacity

[chuck172]

How do you determine a valves flow capacity by its specs?
There are full bore valves, and valves with small orifaces, high restriction valves.
I will be shopping for a 3-way zone valve for my pressurized storage. I have a 1 1/4 honeywell VCZNE6100 in mind.
Like to get full capacity if possible.

 

[steam man]

Valves are given a CV rating which is the flow in gpm at 1 psi pressure drop across the valve. Of course this drop varies with the actual flow so each valve should have a chart showing the actual drop vs. the flow rate. You will need to know this to correctly size your circulator. Some recommend sizing a 3-way valve up 1 size due to the typically higher ressure drop. Compare it both ways to see what size pump you would need. My honeywell 3 way valves came with the charts.

Mike