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Part number 550-110-260/0200
15
Boiler Manual
Water piping — single-zone system3b
Expansion tank
Diaphragm-type or bladder-type
expansion tank — Figure 4
1. Ensure expansion tank size will handle boiler and
system water volume and temperature. Tank must
be located in boiler return piping as close to boiler
as possible, before inlet side of circulator. See tank
manufacturer’s instructions for details.
2. Install an
automatic air vent in air vent tapping as
shown.
Figure 4 Diaphragm- or bladder-type expansion tank
Piping to single-zone system using
diaphragm-type or bladder-type expansion
tank. See Table 3 for piping sizes.
Figure 5 Closed-type expansion tank
Piping to single-zone system using closed-
type expansion tank. See Table 3 for piping
sizes.
Closed-type expansion tank —
Figure 5
1. Ensure expansion tank size will handle boiler and
system water volume and temperature. See tank
manufacturer’s instructions for details.
2. Connect tank to ½" NPT tapping located behind
supply outlet, using ½" NPT piping. Pitch any
horizontal piping up towards tank 1 inch per 5 feet
of piping.
Use Figure 4 or Figure 5 only for single-zone systems designed for return water at least 130 °F.
For systems with low return water temperature possible, such as converted gravity systems
and radiant heating systems, refer to the special piping suggestions of pages 18-23. Failure to
prevent low return water temperature to the boiler could cause corrosion of the boiler sections
or burners, resulting in severe personal injury, death or substantial property damage.
26010
From
system
Cold
water
fill
To DIAPHRAGM
expansion tank
and fittings
Isolation
valve
Isolation
valve
To system
Circulator*
Circulator
Drain
valve
Relief
valve
Automatic
air vent
*Alternate
location
26011
To system
From
system
Isolation
valve
Drain
valve
Relief
valve
Circulator*
Isolation
valve
Circulator
Cold water fill
CLOSED-type
expansion tank
*Alternate
location
Undersized expansion tanks cause system water to be lost from relief valve and makeup water
to be added through fill valve. Eventual section failure can result.