Specifications
Part number 550-142-120/0113
WM97+ gas-fired water boiler — Boiler Manual
– 54 –
Figure 61 WM97+70/110 Chilled water system plus
optional DHW piping
System piping (continued)
Legend — Figure 61
1 WM97+70 or 110 boiler
2 Indirect water heater, if 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
7 System circulator
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
13 Zone valves
14
Primary/secondary by-
pass valve — see page 40 for
information — OPEN: Boiler
connected as primary/second-
ary
15 Supplementary expansion
tank, closed type, REQUIRED
for chiller systems (some
chiller systems may use a dia-
phragm type expansion tank)
16 Water chiller
17 Check valve
18 Y-strainer
19 Balancing valve
20 Make-up water supply
21 By-pass pressure regulator,
RECOMMENDED for zone
valve systems unless other
provision is made
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
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.
WATER CHILLER systems — ZONE VALVES
Internal P/S by-pass valve OPEN
WM97+70 or 110 only
See Figure 61
1. OPEN the boiler internal primary/secondary by-pass valve.
2. The chiller must be piped in parallel with the boiler.
3. Use appropriate valves to prevent chilled medium from entering boiler.
4. Circulator zoning option — The space heating system can be zoned with circula-
tors if a separate circulator is supplied for the chilled water loop. Install a separate
circulator for each zone. The boiler circulator cannot be used for a zone. It must
remain in the boiler, as installed at the factory.
If antifreeze is used in the system, consider the effects of antifreeze on
circulator sizing and DHW performance. Some local codes may require
double-wall DHW heat exchanger design. Use only the antifreeze listed
by Weil-McLain for use with this boiler. See page 88 for details.
Chilled medium, if used, is piped in parallel with heating boiler as shown in
Figure 61. Use appropriate valves to prevent chilled medium from entering
boiler. If boiler is connected to heating coils located in air handling units
where they can be exposed to refrigerated air, use flow control valves or
other automatic means to prevent gravity circulation during cooling cycle.
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 Figure 59, page 52)
if a DHW tank or CWH is NOT connected to the boiler. To provide DHW priority
operation in this case, a Weil-McLain WMZV must be used.
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 61.
Controlling the zones
1. The WM97+ control can be set up to operate on space heating only or on space
heating plus DHW or CWH. Refer to Field wiring, beginning on page 64, for
instructions on wiring to zone valves.
2. The boiler and zone valves can also be operated by a Weil-McLain WMZV
zone controller.
Use isolation relays if connected 3-wire zone valve end
switches to the WM97+ control inputs.
Connect zone valve end switches to ZONE 2 input.
Connect system circulator to CIRC 2 output.