Smith XWH 150 - Page 9

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21. Low Voltage Connection Board: The connection board is
used to connect external low voltage devices.
22. Low Voltage Wiring Connections (Knockouts): Conduit
connection points for the low voltage connection board.
23. Condensate Drain Connection: Connects the condensate
drain line to a 1/2" PVC union.
24. Access Cover - Front (not shown): Provides access to the
gas train and the heat exchanger.
25. Ignition Electrode: Provides direct spark for igniting the
burner.
26. Flame Inspection Window: The quartz glass window
provides a view of the burner surface and ame.
27. Gas Shutoff Valve: Manual valve used to isolate the gas
valve from the gas supply.
28. High limit sensor (housed with the Outlet Temperature
Sensor): Device that monitors the outlet water temperature.
If the temperature exceeds its setting, the integrated control
will break the control circuit, shutting the water heater down.
29. Temperature & Pressure Relief Valve: Protects the heat
exchanger from over pressure and temperature conditions.
The T & P Relief Valve is set at 150 PSI.
30. Flame Sensor: Used by the control module to detect the
presence of burner ame.
31. Line Voltage Wiring Connections (Knockouts): Conduit
connection points for the high voltage junction box.
32. Top Panel: Removable panel to gain access to the internal
components.
33. Power Switch: Turns 120 VAC ON/OFF to the water heater.
34. Leveling Legs: Used to allow the heat exchanger to
be leveled. This is needed for the proper draining of the
condensate from the combustion chamber.
35. Air Shroud (500 Model Only): The air shroud directs air and
gas ow into the burner.
36. Air Pressure Switch: The air pressure switch detects
blocked inlet or outlet conditions.
37. Pump Relay (not shown): The pump relay is used to control
the circulation pump.
38. Transformer: The transformer provides 24V power to the
integrated control.
39. Gas Shutoff Switch: An electrical switch designed to cut
power to the gas valve to prevent releasing any gas.
40. Over-Temp Switch (Models 285 - 800) (located underneath
access cover): An electrical switch designed to shut down
water heater operation in the event the outer back of the
heat exchanger, directly above the ue connection exceeds
604°F (318°C). This is a one time switch and could warrant a
heat exchanger replacement. Check the integrity of the rear
refractory at the back of the upper coil if the switch opens.
41. Burner Door Temperature Switch (Models 285 - 800 Only):
An electrical switch designed to shut down water heater
operation in the event the combustion chamber access cover
exceeds 500°F (260°C). This switch may only be reset by a
qualied service technician AFTER the underlying cause has
been identied and corrected. Check the integrity of the front
refractory on the inside of the combustion chamber access
cover if the switch opens.
COMPONENTS
1. Stainless Steel Heat Exchanger. Allows water to ow
through specially designed coils for maximum heat transfer,
while providing protection against ue gas corrosion. The coils
are encased in a jacket that contains the combustion process.
2. Combustion Chamber Access Cover: Allows access to
the combustion side of the heat exchanger coils.
3. Blower: The blower pulls in air and gas through the venturi
(item 5). Air and gas mix inside the blower and are pushed
into the burner, where they burn inside the combustion
chamber.
4. Gas Valve: The gas valve monitors the negative pressure
created by the blower, allowing gas to ow only if the gas
valve is powered and combustion air is owing.
5. Venturi: The venturi controls air and gas ow into the
burner.
6. Flue Gas (limit rated): This sensor monitors the ue gas
exit temperature. The control module will modulate and
shut down the water heater if the ue gas temperature gets
too hot. This protects the ue pipe from overheating.
7. Water Heater Outlet Temperature Sensor (Housed with
the High Limit Sensor): This sensor monitors water heater
outlet water temperature (system supply). If selected as
the controlling sensor, the control module adjusts the water
heater ring rate so the outlet temperature is correct.
8. Water Heater Inlet Temperature Sensor: This sensor
monitors return water temperature (system return). If
selected as the controlling sensor, the control module adjusts
the water heater ring rate so the inlet temperature meets
system setpoint.
9. Flow Switch: The ow switch is a safety device that ensures
ow through the heat exchanger during operation. This
appliance is low mass and should never be operated without
ow. The ow switch makes contact when ow is detected
and allows the unit to operate. If ow is discontinued during
operation for any reason the ow switch will break the control
circuit and the unit will shut down.
10. Touch Screen Display: The electronic display is a Touch
Screen Display consisting of Main Menu, Help and Enable/
Disable buttons.
11. Flue Pipe Adapter: Allows for the connection of the PVC
vent pipe system to the water heater.
12. Burner (not shown): Made with metal ber and stainless
steel construction, the burner uses pre-mixed air and gas
and provides a wide range of ring rates.
13. Water Outlet: NPT water connection that supplies hot water
to the tank.
14. Water Inlet: NPT water connection that returns water from
the tank to the heat exchanger.
15. Gas Connection Pipe: Threaded pipe connection. This
pipe should be connected to the incoming gas supply for the
purpose of delivering gas to the water heater.
16. Control Module: The Control Module responds to internal
and external signals and controls the blower, gas valve, and
pumps to meet the demand.
17. Manual Air Vent: Designed to remove trapped air from the
heat exchanger coils.
18. Air Intake Adapter: Allows for the connection of the PVC air
intake pipe to the water heater.
19. High Voltage Junction Box: The junction box contains the
connection points for the line voltage power and the pump.
20. Water Heater Drain Port: Location from which the heat
exchanger can be drained.