Hoffman Main Vents

HenryT

Hi All. I am intending to build a "tree" to purge the air out of my main vents.

Staying true to the statement you cant overvent, I want to add 2 Hoffman 75 main vents to my system. 

Is there a difference between hoffman 75H and hoffman 75? The 75h is rated for high pressure.



The reason im asking is because my local supply store has the 75H for a considerably cheaper price. The specs and NPT are all the same as the 75.

Any expert care to chime in?



Thanks

crash2009

Dont buy either one

until you figure out how many you need, and what capacity and specification.  Get the venting capacity chart http://www.heatinghelp.com/products/Books/5/146/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-by-Gerry-Gill-and-Steve-Pajek