Demand Duo
™
R
-
Series Installation and Operation Manual
45
1 6
Over Temperature Warning
(Safety shutdown because unit is too
hot)
•
Check for restrictions in air flow around
unit and vent terminal.
•
Check for low water flow in a circulating
system causing short
-
cycling.
•
Check for foreign materials in
combustion chamber and/or exhaust
piping.
•
Check for blockage in the heat
exchanger.
1 9
Electrical Grounding
•
Check all components for electrical
short.
3 2
Outgoing Water Temperature Sensor
3 3
Heat Exchanger Outgoing Temperature
Sensor
•
Check sensor wiring for damage.
•
Measure resistance of sensor.
•
Clean sensor of scale build
-
up.
•
Replace sensor.
3 4
Combustion Air Temperature Sensor
•
Check for restrictions in air flow around
unit and vent terminal.
•
Check sensor wiring for damage.
•
Measure resistance of sensor.
•
Clean sensor of scale build
-
up.
•
Ensure fan blade is tight on motor shaft
and is in good condition.
•
Replace sensor.
5 1
Inlet water temperature thermistor
•
Check sensor wiring for damage.
•
Measure resistance of sensor.
•
Clean sensor of scale build
-
up.
•
Replace sensor.
5 2
Modulating Solenoid Valve Signal
•
Check modulating gas solenoid valve
wiring harness for loose or damaged
terminals.
•
Measure resistance of valve coil.
1 2
No Flame
•
Check that the gas is turned on at the
water heater, gas meter, or cylinder.
•
Check for obstructions in the flue outlet.
•
If the system is propane, make sure that
gas is in the tank.
•
Ensure gas line, meter, and/or regulator
are sized properly.
•
Ensure gas type and pressure are
correct.
•
Bleed all air from gas lines.
•
Ensure proper venting material was
installed.
•
Check power supply for loose
connections.
•
Check power supply for proper voltage
and voltage drops.
•
Ensure flame rod wire is connected.
•
Check flame rod for carbon build
-
up.
•
Disconnect and reconnect all wiring
harnesses on unit and PC board.
•
Check for DC shorts at components.
•
Check gas solenoid valves for open or
short circuits.
•
Remove burner plate and inspect burner
surface for condensation or debris.
1 4
Thermal Fuse has activated
•
Check for restrictions in air flow around
unit and vent terminal.
•
Ensure dip switches are set to the proper
position.
•
Ensure dip switch 5 in the second bank
of dip switches (white) is in the off
position.
•
Check gas type of unit and ensure it
matches gas type being used.
•
Check for low water flow in a circulating
system causing short
-
cycling.
•
Check for foreign materials in
combustion chamber and/or exhaust
piping.
•
Check heat exchanger for cracks and/or
separations.
•
Check heat exchanger surface for hot
spots which indicate blockage due to
scale build
-
up. Refer to instructions in
manual for flushing heat exchanger.
•
Hard water must be treated to prevent
scale build up or damage to the heat
exchanger.
•
Measure resistance of safety circuit.
•
Ensure high fire and low fire manifold
pressure is correct.
•
Check for improper conversion of
product.
