Closed system and NPSHa

When selecting a pump for a closed loop hot water system, how do you calculate the NPSHa?

NPSHa = Static Height - Inlet Friction - 3’ Safety Factor

Is the static height calculated from the highest point in the system?

For inlet friction, how far back in the pipe line do you go to calculate this?


As this is a closed loop system and without being too pedantic - the NPSHa is the discharge pressure from the pump less all the losses in the system back to the inlet.

Above is a snippet.