(2) Locate the tank on the suction side of the
system pump so that system pressure is always positive with
respect to atmospheric pressure.
(3) Do not install a shutoff valve between the
heat source and the expansion tank.
(4) Refer to ASHRAE Handbook, HVAC Systems and
Application or manufacturer's literature for tank sizing.
See Figure 14 for closed expansion tank
See Figure 15 for diaphragm expansion tank
(7) Do not use a gage glass on the expansion tank.
A gage glass on a steam boiler is permitted since the wet steam
vapor keeps the upper glass packing tight. With an expansion
tank, the air will dry out the upper gage glass packing and cause
Domestic Hot Water Generator. An interface occurs
between the heating system and the plumbing system when boiler
steam or boiler hot water is used to heat water for plumbing
fixtures. Some points to consider in heating domestic hot water
are as follows:
a) Domestic water can be heated by the boiler (steam
or hot water) or a separate hot water generator, if the heating
source is available during the summer. If heated by the space
heating boiler, evaluate boiler efficiency for summer operation.
b) If the space heating boiler provides hot water,
evaluate if it should be an instantaneous heater, a semi-
instantaneous heater, or a storage type hot water generator. The
selection will affect the boiler capacity specified. Refer to
NAVFAC DM-3.01, Plumbing Systems for domestic hot water system
With these decisions made, select the hot water system
and equipment. See Figure 16 and Figure 17.
Heat Exchangers. Heat exchangers are used for steam to
heat water. One medium flows through the shell, and the other
medium flows through the tubes in the tube bundle. Include the
following in the equipment schedule: