> Posted for Jim Sower <canarder@starband.net>:
>
> I thought that in a closed system there was no head pressure.  If the
system
> is
> pressurized, there is system pressure, but still no head pressure.  The
closed
> loop
> cancels everything out.
> Just wonderin' .... Jim S.
>

Nope.  There is still differential pressure in a closed system with
restrictions in it.  The pump sees the restrictions as head pressure.

Tracy