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The Shield - How it works...
1. Access cover - front
Provides access to the gas train and heat exchanger.
2. Air intake adapter
Allows for the connection of the PVC air intake pipe to
the water heater.
3. Air pressure switch
The air pressure switch detects blocked inlet conditions.
4. Air shroud (500-125 Model Only_Not Shown)
The air shroud directs air and gas flow into the blower.
5. 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.
6. Burner (not shown)
Made with metal fiber and stainless steel construction,
the burner uses pre-mixed air and gas and provides a
5 to 1 firing rate.
7. Condensate drain connection
Connects the condensate drain line to 1/2" PVC.
8. Electronic Control Module
The electronic control responds to internal and external signals
and controls the blower, gas valve, and pumps to meet the
demand.
9. Electronic display
The electronic display consists of 7 buttons and a dual line 32-
character liquid crystal display.
10. Flame inspection window
The quartz glass window provides a view of the burner
surface and flame.
11. Flame sensor
Used by the control module to detect the presence of burner
flame.
12. Flue gas sensor (not shown)
This sensor monitors the flue gas exit temperature. The control
module will modulate and shut down the water heater if the
flue gas temperature gets too hot. This protects the flue pipe
from overheating.
13. Gas connection pipe
Threaded pipe connection, either 1/2", 3/4", or 1",
depending on the model. This pipe should be connected
to the incoming gas supply for the purpose of delivering
gas to the water heater.
14. Gas shutoff switch (150-100 - - 285-125 Models Only)
An electrical switch designed to cut power from the gas valve to
prevent gas flow to the burner.
15. Gas shutoff valve (400-125 -- 500-125 Models Only)
Manual valve used to isolate the gas valve from the gas supply.
16. Gas valve
The gas valve senses the negative pressure created by the
blower, allowing gas to flow only if the gas valve is
powered and combustion air is flowing.
17. Heat exchanger access cover
Allows access to the combustion side of the heat
exchanger coils.
18. Heat exchanger inlet temperature sensor
This sensor monitors the inlet water temperature to the heat
exchanger.
19. Heat exchanger outlet temperature sensor
This sensor monitors heat exchanger outlet water temperature.
20. High limit sensor
Device that monitors the outlet water temperature. If the
temperature exceeds its setting, it will break the control circuit,
shutting the water heater down.
21. Ignition electrode
Provides direct spark for igniting the burner.
22. Line voltage junction box
The junction box contains the connection points for the line
voltage power.
23. Low voltage connection board
The connection board is used to connect external low voltage
devices.
24. Low voltage wiring connections (knockouts)
Conduit entryway for the low voltage
connection board.
25. Power cord
Six foot cord allows for quick connection to 120V supply.
26. Pump
Circulates water between the tank and the heat exchanger.
27. Pump relay
Switches power to the pump.
28. Relief valve discharge pipe
Protects the heat exchanger from over pressure and
temperature conditions. The relief valve is set at 150 PSI.
29. Stainless steel heat exchanger
Allows water to flow through specially designed
coils for maximum heat transfer, while providing
protection against flue gas corrosion. The coils are
encased in a jacket that contains the combustion process.
30. Tank sensor
Used by the control to monitor the temperature of the tank.
31. Top panel
Removable panel to gain access to the internal components.
32. Vent pipe connection
Allows for the connection of the PVC/CPVC vent pipe system
to the water heater.
33. Venturi
The venturi controls air and gas flow into the burner.
34. Water heater drain valve
Location from which the water heater can be drained.
35. Water inlet
Copper sweat connection for cold water supply that returns
water from the system to the heat exchanger, either 1-1/2" or 2",
depending on the model.
36. Water outlet
Male NPT water connection that supplies hot water to the
system, either 1-1/2" or 2", depending on the model.
Installation & Service Manual
TM