Weil-McLain WM97+110, Manual, Page: 45 / 132

Part number 550-142-085/0712
– 45 –
WM97+
gas
-
fired water boiler
— Boiler Manual
Figure 50 WM97+155
Zone valve zoning —
primary/secondary connection —
a system circulator is required
The boiler primary/secondary by-pass valve
MUST be OPEN
for
single-boiler WM97+155 applications, with system connected
as primary/secondary.
See Figure 50.
1.
OPEN
the boiler internal primary/secondary by-pass valve.
2. Install a system circulator (supplied by installer) as shown.
3. A benefit of primary/secondary piping is that it does not apply the head
of the boiler circulator to the system zone valves.
Expansion tank required
1. Provide a system expansion tank following the guidelines on page 41.
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 boiler’s bottom connec-
tions to water heater boiler connections as shown. See CWH manual for
CWH piping instructions.
2. DHW as a zone — A DHW tank can be connected as a zone 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 heat-
ing 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 50.
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 62, for instructions on wiring to zone valves.
2. The boiler and zone valves can also be operated by a Weil-McLain
WMZV zone controller.
System piping
(continued)
Legend — Figure 50
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 37
5
DHW circulator
6
Isolation valves
7
System circulator
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
13
Zone valves
14
Primary/secondary by-
pass valve — see page 39 for
information — OPEN: Boiler
connected as primary/sec-
ondary
20
Make-up water supply
21
By-pass pressure regulator,
RECOMMENDED for zone
valve systems unless other
provision is made
23
Backflow preventer, when
used
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
Connect zone valve end switches to ZONE 2 input.
Connect system circulator to CIRC 2 output.
Use isolation relays if connected 3-wire zone valve end
switches to the WM97+ control inputs.
DHW refers to an indirect-fired domestic hot
water storage tank. CWH refers to a Weil-
McLain Companion Water Heater.
ZONE VALVE zoning — primary/secondary
Internal P/S by-pass valve OPEN
WM97+155 only