Weil-McLain 550 MBH Nstallation And Operation Manual page 14

®
SlimFit Series 3
Install water piping
Expansion tank and make-up water
1. Ensure expansion tank size will handle boiler and system
water volume and temperature. Allow 7 gallons per boiler
for the 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.
2. Tank must be located as shown in this manual, or following
recognized design methods. See tank manufacturer's instruc-
tions for details.
3. Connect the expansion tank to the air separator only if the
separator 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.
4. Most piping drawings in this manual show diaphragm ex-
pansion tanks. See Figure 6 for piping from air separator to
expansion tank and make-up water line using a closed-type
expansion tank.
5. Most chilled water systems are piped using a closed-type tank,
as shown in Figure 11, page 19.
Diaphragm (or bladder) expansion tank
1. (Figure 6) 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
1. See Figure 6, Alternate, for piping connections when using a
closed-type expansion tank.
2. Pitch any horizontal piping up towards tank 1 inch per 5 feet
of 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 automatic air vent would cause air to
leave system, resulting in water-logging the expan-
sion tank.
Install a union on the boiler supply and return
connections as close as possible to the boiler to
allow disconnection for service when required.
See Figure 6.
14
COMMERCIAL CONDENSING GAS
(continued)
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FIRED WATER BOILER
Expansion tank piping
Boiler Manual
Part number 550-100-168/0516