Water pressure drop
Coil face velocity
Any special requirements
After the coil selection has been made and documented
in the design analysis, be sure to provide the above data in the
coil schedule on drawings. This will ensure a good bidding
climate, with equipment manufacturers knowing what to bid, and
what to submit in the shop drawings phase.
Expansion Tanks and Air Separator
a) Expansion Tanks General. When water in a hot water
System pressure control is needed to:
(1) Limit pressure in all parts of the system to
the allowable working pressure.
(2) Maintain minimum pressure in the system to
prevent pump cavitation and to prevent boiling of system water.
Minimize addition of makeup water.
b) Expansion Tank With Air Separator. An expansion
tank with an air separator performs these system pressure control
functions. Since this section does not address medium
temperature hot water system (250 to 350 degrees F) or high
temperature hot water system (above 350 degrees F); discussion
will be limited to the following types of tanks:
Closed expansion tanks with an air cushion.
See Figure 14.
(2) Diaphragm (or bladder) type closed expansion
See Figure 15.
Open expansion tanks located at the system high point
will also work on low temperature hot water systems, but are not
generally used on Navy building projects.
c) Expansion Tanks. Some specifics regarding
expansion tanks are as follows:
(1) Expansion tanks are required on chilled water
and hot water systems.