Specifications

Part number 550-142-120/0113
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WM97+ gas-fired water boiler — Boiler Manual
Figure 58 WM97+155 Typical radiant heating
system piping — circulator zoning
System piping (continued)
Legend — Figure 58
1 WM97+155 boiler
2 Indirect water heater, when
used (for CWH installations,
refer to the Weil-McLain
CWH manual)
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
5 DHW circulator
6 Isolation valves
8 System expansion tank, dia-
phragm type, when used
9 Air separator
10 Flow/check valves
11 Purge/drain valves (one drain
valve is supplied loose with
the boiler)
12
Boiler circulator, with inte-
gral flow/check valve, factory
installed in boiler
14
Primary/secondary by-
pass valve — see page 41 for
information — OPEN: Boiler
connected as primary/second-
ary
20 Make-up water supply
22 High limit temperature con-
trol
23 Backflow preventer, when
used
24 Zone circulators
25 Pressure reducing valve, when
used
27 Quick-fill valve, when 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
31 Heating circuits
32 Additional heating circuits, if
any
= Items supplied with boiler
— all other items supplied by
installer
DHW refers to an indirect-fired domestic hot
water storage tank. CWH refers to a Weil-
McLain Companion Water Heater.
RADIANT HEATING — CIRCULATOR zoning
Internal P/S by-pass valve OPEN
WM97+155 only
See Figure 58 .
1. The WM97+ boiler is ideal for use in radiant heating. The unique heat exchanger
design allows it to work well even in condensing mode. There is no need to
regulate boiler return water temperature in radiant heating applications.
2. Apply this configuration for typical radiant heating applications.
3. Size the system piping and circulators to provide the flow and pressure drop
needed.
High limit in system piping
1. Add the recommended high limit control (Figure 58, item 22) to help ensure
supply water temperature will not exceed the maximum allowable for the radi-
ant system.
2. Wire the limit control to either the manual reset or automatic reset external
limit circuit of the WM97+ control.
Expansion tank
1. Provide a system expansion tank following the guidelines on page 43.
2. DO NOT use a closed-type tank if connecting to a water heater that is equipped
with an automatic air vent.
DHW or CWH, if used
1. DHW or CWH direct connection — Pipe from the boiler’s bottom connections
to water heater boiler connections as shown. See the CWH manual for CWH
piping instructions.
2. DHW tank as a zone — A DHW tank can be piped as a zone (as in Fig-
ure 60, page 53) if a DHW tank or CWH is NOT connected to the boiler. Wire
the DHW circulator to boiler Zone 1. Set the boiler circulator to ON in the
DHW Settings menu.
3. Priority option — By default, the WM97+ control turns off space heating to
its Zone 2 and Zone 3 outputs during domestic water heating on Zone 1. The
MAX ON TIME setting can be adjusted to limit how long this occurs. Set the
MAX ON TIME to “0” to disable domestic priority.
4. If NOT connecting a water heater, terminate the bottom connections as shown
in the inset on Figure 58.
Controlling the zones
1. The WM97+ control operates up to three zones (DHW or CWH plus two space
heating, or three space heating). Refer to Field wiring, beginning on page 64, for
instructions on wiring to circulators.
2. For more than three zones, use a Weil-McLain WMCR zone controller. See
suggested wiring in this manual.