Weil-McLain WM97+110-CT, Manual

Page: 42 / 136

Part number 550-142-120/1113
WM97+
gas
-
fired water boiler
— Boiler Manual
– 42 –
Supplementary expansion tank, if required
—
systems having volumes more than 15 gallons only
1. The boiler is equipped with an internal diaphragm-type expansion
tank, factory charged to 12 PSIG.
a. The internal tank is suitable for systems up to 15 gallons, not in-
cluding the volume of water in the boiler and its internal piping.
b. This should be adequate for finned-tube baseboard systems and
most radiant heating systems.
c. Existing expansion tanks should be left in place even if additional
expansion tank capacity is not needed for the system.
For larger volume systems, such as systems with radia-
tors or cast iron baseboard, provide an additional expan-
sion tank sufficient for the system volume
. 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 ad-
dition.
2. If the system does not have an existing expansion tank, add a dia-
phragm or bladder-type tank, piped as in Figure 46. Always install an
automatic air vent on top of the air separator to remove residual air
from the system.
If using diaphragm or bladder tanks only — if 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.
Follow the expansion tank manufacturer’s sizing and applica-
tion guidelines
Existing expansion tanks
1. An existing expansion tank should be piped as in Figure 46 for dia-
phragm or bladder-type tanks, or Figure 47 for a closed-type expan-
sion tank.
DO NOT install automatic air vents on closed-type expan-
sion 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 expansion tank. DO NOT use a closed-type tank if con-
necting to a water heater that is equipped with an automatic
air vent
If possible, replace an existing closed-tanks with a diaphragm
or bladder-type expansion tank. Closed-type tanks often
cause air removal problems.
Expansion tank — WM97+70 and 110
Figure 46 WM97+70/110
external expansion tank
piping, diaphragm or bladder-type
Figure 47
WM97+70/110
external expansion tank
piping, closed-type expansion tank
LEGEND for Figure 46 and Figure 47
1 WM97+ boiler
3 Relief valve, supplied with boiler, field piped —
MUST be piped to boiler supply connection —
see page 13 for information
4 Relief valve piping to drain — see page 39
6 Isolation valves
8 Supplementary expansion tank, diaphragm
type, if used
9 Air separator
10 Flow/check valve (in boiler circulator)
11 Purge/drain valves
12 Boiler circulator
14 Primary/secondary by-pass valve — see
page 40 for information
15 Supplementary expansion tank, closed-type,
if used
20 Make-up water supply
23 Backflow preventer, if used
25 Pressure reducing valve, if used
26 Internal expansion tank, diaphragm-type
27 Quick-fill valve, if used
28 DHW boiler water supply connection, when
used — see page 13 for information
29 DHW boiler water return connection, when
used — see page 13 for information
30 Pressure/temperature gauge, supplied with
boiler, field piped