The Wm97+70 & 110 Gas-Fired Water Boilers - Weil-McLain WM97+70 Manual

WM97+ -
gas fired water boiler
The WM97+70 & 110 Gas-fired water boilers
1. Stainless steel firetube heat exchanger
2. Heat exchanger access cover/burner mounting plate
3. Blower
The advanced blower design and air inlet silencer on WM97+ boilers
result in very quiet operation.
Air enters the boiler enclosure through the air intake adapter (18),
flows through the enclosure, enters the air inlet silencer (5), then
enters the blower. The blower pulls air through the silencer and
pushes it into the venturi (6), where it mixes with gas before enter-
ing the burner.
4. Gas valve
The automatic gas valve (4) senses the vacuum in the venturi caused
by flowing air, and allows gas to flow when power is applied. A
manual gas valve is shipped loose with the boiler. It allows shutting
off the gas supply for servicing or shutdown. See instructions in this
manual for manual gas valve installation.
5. Air inlet silencer
The horn-shaped air inlet silencer significantly reduces fan noise,
providing exceptionally quiet operation.
6. Venturi
When air flows through the venturi, it creates a negative pressure.
This vacuum pulls gas from the gas valve. So gas will only flow if
air is flowing. The gas mixes with air in the venturi. The gas/air
mixture then flows into the burner.
7. Outlet water temperature dual sensor
This dual sensor monitors boiler outlet water temperature. The
WM97+ control adjusts boiler firing rate so the outlet water tem-
perature is correct, based on the calculated (if outdoor reset used
— see page 129) or fixed target temperature.
8. Return water temperature sensor
This sensor monitors return water temperature. The WM97+
control reduces or increases boiler input, depending on how close
the return water temperature is to the outlet water temperature.
9. DHW tank or CWH piping connections
An indirect storage water heater can be piped to these connections
for direct connection to the boiler. The installer must supply the
circulator for a DHW boiler water loop. CWH (Companion Water
Heater) units are shipped with a circulator.
10. Electronic display & buttons
The electronic display is used to configure boiler settings and moni-
tor boiler operation.
The buttons allow changing display mode, selecting and adjusting
control settings, and resetting the control after lockout.
11. Flue adapter (fits 3" PVC)
12. Burner
Made with high-grade stainless steel construction, the burner uses
pre-mixed air and gas. The burner and control provide modulat-
ing firing.
13. Water outlet pipe (system supply)
14. Water return pipe (system return)
15. Gas connection pipe
Manual gas valve is shipped loose. Other ½" NPT gas connection
pipe and fittings (including union) shown must be supplied by
the installer.
16. WM97+ control
The responds to signals from the room thermostats,
WM97+ control
DHW aquastats (if used), boiler sensors (boiler return, boiler supply,
flue temperature, and outdoor temperature, if used — see page 129).
The control automatically adjusts blower speed (and gas flow rate)
– 2 –
— Boiler Manual
to match boiler output to space heating and/or DHW heating
demand. The control provides for three heating zones (DHW plus
two space-heating or three space heating). DHW direct-connected
to the bottom piping connections can be set for domestic priority.
17. Multi-position WM97+ control housing
The WM97+ control is mounted in a plastic housing assembly that
can rotate forward for rear access to the control boards or for access
to boiler components. It can also be removed through slots in the
boiler jacket sides.
18. Air intake adapter (fits 3" PVC)
19. Electrical entrances
The left side electrical enclosure (19a) houses the line voltage ter-
minal block. The right side electrical enclosure (19b) houses low
voltage terminals.
20. Boiler drain valve (not shown)
Shipped loose for field piping to DHW return line at bottom of
boiler jacket. See instructions in this manual.
21. Integral expansion tank
The 3.2-gallon internal expansion tank is factory installed as shown.
It is supplied with an isolation valve that allows removal for service
or replacement without draining the system or boiler.
22. Flue gas condensate drain
Flexible plastic hose is provided to adapt to 1" PVC (fits in 1" PVC
coupling).
23. Flue gas condensate drain trap assembly
The condensate trap assembly is field-installed, connected to the
condensate trap nozzle as shown in this manual.
24. Front door
The front door is sealed to the boiler assembly around its entire
perimeter.
25. Front door latches
Two latches secure the door in place.
26. Ignition electrode/flame sensor
The burner flame is ignited by applying a high voltage to the igni-
tion electrode. This causes a spark (from electrode to ground). After
ignition, the electrode measures flame signal.
27. Flame inspection window
The quartz glass window provides a view of the burner surface, the
flame, and the ignition electrode.
28. Flue gas dual sensor
This dual sensor monitors the flue gas exit temperature. The
WM97+ control will shut down the boiler if flue gas temperature
gets too hot. This protects the flue pipe and the heat exchanger
from overheating.
29. ON/OFF switch
30. Primary/secondary shut-off valve
Supply and return from the heating system are connected to the
pipes out the top of the boiler. When p/s shut-off valve is open, the
piping connection is primary/secondary, requiring a separate circu-
lator for the system. When the valve is closed, the boiler circulator
is used for boiler and system flow.
31. Low water cut-off
32. Boiler circulator
33. Gas valve reference hose
This rubber line connects the gas valve diaphragm reference
chamber to the venturi intake to insure the valve senses the correct
reference pressure.
Part number 550-142-085/0712