- #1

russ_watters

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## Main Question or Discussion Point

I'm having a slow day (pun intended) today, and I need a little help. I'm getting pound-mass and pound-force mixed up in my head. On a psychrometric chart, it just says "pounds", but is 14 lb/ft^3 the

VP=4005 V^1/2

VP = velocity pressure in inchess of water

V = Velocity of air in feet per minute

So where does the 4005 come from...?

**mass**or**weight**density of air? I've been using cheater equations for the past few years, but now I need to do derive the typical hvac cheater equation for pressure vs velocity:VP=4005 V^1/2

VP = velocity pressure in inchess of water

V = Velocity of air in feet per minute

So where does the 4005 come from...?