Installation Guide
Part number 550-100-066/0608
g a s -f i r e d w at e r b o i l e r — Boiler Manual
16
Install water piping (continued)
Expansion tank and make-up water
Ensure expansion tank size will handle boiler and system water vol-1.
ume and temperature. Allow 3 gallons for boiler and its piping.
Undersized expansion tanks cause system water to be
lost from relief valve and make-up water to be added
through fill valve. Eventual boiler failure can result due
to excessive make-up water addition.
Tank must be located as shown in this manual, or following rec-2.
ognized design methods. See tank manufacturer’s instructions
for details.
Connect the expansion tank to the air separator only if the separa-3.
tor is on the suction side of the circulator. Always install the system
fill connection at the same point as the expansion tank connection
to the system.
Most piping drawings in this manual show diaphragm expansion 4.
tanks. See Figure 14 for piping from air separator to expansion tank
and make-up water line using a closed-type expansion tank.
Most chilled water systems are piped using a closed-type tank, as 5.
shown in Figure 19, page 21.
Diaphragm (or bladder) expansion tank
(1. Figure 14) Always install an automatic air vent on top of the air
separator to remove residual air from the system.
When using diaphragm or bladder tanks only — when the
boiler is installed above the system main piping, install
an automatic air vent in the top of the outgoing boiler
piping to prevent air pocketing.
Closed-type expansion tank
See 1. Figure 14, Alternate, for piping connections when using a
closed-type expansion tank.
Pitch any horizontal piping up towards tank 1 inch per 5 feet of 2.
piping. Connect to tank with at least ¾” piping to allow room for
air to rise.
DO NOT install automatic air vents on closed-type
expansion tank systems. Air must remain in the system
and return to the tank to provide its air cushion. An au-
tomatic air vent would cause air to leave system, resulting
in water-logging the expansion tank.
Expansion tank piping