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Weil-McLain 94 Series 3 Water and steam boilers — for Gas, Light Oil, & Gas/Light Oil-Fired Burners
14 Part No. 550-110-275/1018
Connect water boiler piping
General water piping information
1. System water supply and return piping should be installed and
piping connections attached to boiler before erecting jacket or
installing controls.
2. Do not pipe in through supply and out through return. This creates
reverse water flow through boiler that must not be used.
3. When installing in a system in which return water temperature can
drop below 140°F, apply the by-pass piping with by-pass pump as
shown in Figure 16, page 15.
4. When three-way valves are used for temperature modulation,
install slow-opening valves to minimize the potential of boiler
thermal shock.
Install piping
Install piping as shown in Figure 12, page 14 and Figure 16, page 15
(if applicable) for single boilers. For multiple boilers, see Fig-
ure 17, page 15.
Improperly piped systems or undersized piping can
contribute to erratic boiler operation and possible boiler
or system damage.
1. Connect supply and return piping:
a. Size according to tables below.
• For
known flow rates or higher flow rate (less than 20°F
temperature rise) through boiler, see Figure 13.
• For
unknown flow rates, size piping per Figure 15, page 15,
using 20°F temperature rise through boiler.
Flow at higher rates than shown in the tables in this
manual for given pipe sizes can damage the boiler, caus-
ing substantial property damage.
b. Locate circulator in supply piping.
c. For return piping, use full diameter pipe for 10 times that
diameter before making any reduction. For example, a 4-inch
return should not be reduced any closer to boiler return tap-
ping than 40 inches.
d. Install system blow-off (drain) valve in lowest part of return
piping close to boiler. ASME minimum size requirements are
given in Figure 15, page 15.
2. Install expansion tank:
a.
Closed type – connect to 1
1
⁄4" tapping T1, T2 or X2 (see
Figure 10, page 12). Use 1" NPT piping. Any horizontal pip-
ing must pitch up toward tank at least 1 inch per each 5 feet
of piping.
b.
Diaphragm type – Refer to tank manufacturer's literature for
location. Install automatic air vent in 1
1
⁄4" tapping T1, T2 or
X2 (see Figure 10, page 12).
c. Connect cold water fill to expansion tank piping. Figure 12
shows typical piping when using a closed type tank. Connect
to the same location as the expansion tank connects to the
system when using a diaphragm type tank.
d. Also shown are recommended valves and water meter, when
used. Water meter will detect added make-up water, indicating
leaks in system.
Figure 12 Water boiler piping, typical
Figure 13 Recommended minimum pipe sizes for
known flow rates
(note 1)
Water flow
rate, GPM
Supply pipe size
A
Return pipe size
B
up to 77
3" 3"
78 – 132
4" 4"
133 – 208
5" 5"
209 – 300
6" 6"
301 – 520
8" 8"
521 – 820
10" 10"
Note 1 High temperature rise through boiler is permissible when boiler
piping connections are sized per this table.
Intermittent flow at high velocities may damage any
boiler.
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