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INSTALLATION INSTRUCTIONS

34-00013EF-01

WT8840 
Trade Water Heater Controls

APPLICATION

The WT8840 Water Heater Control is designed for use 
in Standing Pilot applications using an immersion 
well for water temperature sensing. All models of 
WT8840 include an integrated NTC temperature 
sensor.

The WT8840 is powered from a thermopile heated by 
the standing pilot flame. CS8840 pilot assemblies are 
designed for use with this control.

The immersion well for sensing water temperature 
has matched NTC thermistor sensors. These sensors 
provide the fail-safe mechanism through which the 
WT8840 can provide both accurate water 
temperature control as well as water temperature 
limit (Temperature Cut-Out [TCO]) function.

SPECIFICATIONS

IMPORTANT

WT8840 controls provide direct replacement 
only.

Pressure Regulator: 

The outlet pressure regulator 

setting is shown on the product label.

Inlet Pressure Range:

See appliance rating plate for inlet pressure range 

recommendation. 

0.5 PSI (14.0 in. w.c.) maximum inlet pressure 

allowed for proper operation.

Body Pattern:

 90 degrees with 1/2 in. inlet and 

1/2 in. inverted flare outlet.

Mounting: 

Mounting in upright position only.

Control Input:

Voltage Minimum: 350 mV dc, open circuit.
Voltage Maximum: 850 mV dc, open circuit.

Capacity: 

See Table 1.

Regulation Range:

Natural Gas:
   Minimum: 30,000 Btuh.
   Maximum: 85,000 Btuh.

Ambient Temperature Range: 

32 to 150 °F 

(0 to 66 °C)

Operating Range: 

0 to 150 °F (-18 to 66 °C)*

*Valve will operate at 0°F (-18°C) but valve 

characteristics can not be guaranteed until 
ambient temperature reaches 32°F (0°C).

Storage Range: 

-40 to 150 °F (-40 to 66 °C)

Humidity: 

95% non-condensing at 104 °F (40 °C)

Approvals:

This device is certified by Canadian Standards 

Association (CSA) to the following standards:
ANSI Z21.20
ANSI Z21.23
ANSI Z21.78
ANSI Z21.87
CAN/CSA-C22.2 No. 199-M89
CAN1-6.6-M78
CSA 4.6
CSA 6.20

Accessory Parts:

Pilot Assembly CS8840

Trade Service Part

Replaces

WT8840A1000

WV8840A1000

WV8840A1001

WT8840A1500

WV8840A1050

WV8840A1051

WT8840B1000

WV8840B1042

WV8840B1109

WV8840B1110

WT8840B1500

WV8840B1059

WV8840B1117

WV8840B1118

Summary of Contents for WT8840

Page 1: ...ressure range recommendation 0 5 PSI 14 0 in w c maximum inlet pressure allowed for proper operation Body Pattern 90 degrees with 1 2 in inlet and 1 2 in inverted flare outlet Mounting Mounting in upright position only Control Input Voltage Minimum 350 mV dc open circuit Voltage Maximum 850 mV dc open circuit Capacity See Table 1 Regulation Range Natural Gas Minimum 30 000 Btuh Maximum 85 000 Btuh...

Page 2: ...ded in air as in some industrial or agricultural applications protect the control with a cover Dust or Grease Accumulation Heavy accumulations of dust or grease can cause the control to malfunction Where dust or grease can be a problem provide covers for the control to limit contamination Heat Excessively high temperature can damage the control Make sure the maximum ambient temperature at the cont...

Page 3: ...es 1 Use a new properly reamed pipe free from chips If tubing is used make sure the ends are square deburred and clean All tubing bends must be smooth and without deformation 2 Ensure that gas supply is turned off 3 Run pipe or tubing to the water heater control If tubing is used obtain a tube to pipe coupling to connect the tubing to the control 4 Install a sediment trap in the supply line to the...

Page 4: ...feet of 1 2 in pipe with 5 in w c pressure 2 Depress the piezo igniter to light the pilot flame and hold the knob in until the status indicator starts to blink approximately 30 seconds indicating pilot now being held by electronics NOTE LED should blink once every three seconds If not check the error codes in Table 3 3 Release the knob and turn to the desired temperature setting The burner will co...

Page 5: ...s Leak Test at plug with main burner operating Procedure to check the gas input and burner flow rate 1 Check the full rate manifold pressure listed on the appliance nameplate Water heater control full rate outlet pressure should match this rating 2 With burner operating check the water heater control flow rate using the meter clocking method or check pressure using a manometer connected to the out...

Page 6: ...Normal operatio n No action required 1 flash every 3 seconds Not an error indicates the electronics is holding the Pilot Valve open and the Main Valve closed You can now turn the knob to a desired setpoint temperature LED will continue to flash 1 time every 3 seconds while in Idle mode no call for heat Strobe every 3 seconds Not an error indicates call for heat during normal operation Main valve o...

Page 7: ...DEVICE KNOB FROM OFF TO PILOT PRESS DOWN KNOB AND HOLD LIGHT PILOT BY DEPRESSING PIEZO IGNITION BUTTON PILOT SHOULD LIGHT WATER TEMPERATURE IS BELOW THE CUT OUT LIMIT CHECK WIRING OF THERMOPILE LEADS FLAME COVERAGE OF THERMOPILE THERMOPILE OUTPUT IS TOO LOW RUN THERMOPILE OUTPUT CHECK STATUS LIGHT SHOULD FLASH AFTER 1 MINUTE LED WILL FLASH NORMAL SINGLE BLINK RELEASE THE DEVICE KNOB PILOT SHOULD R...

Page 8: ... heated water IMPORTANT Follow the operating instructions provided by the manufacturer of your water tank appliance The information in this form describes a typical water heater control application but the specific controls used and the procedures outlined by the manufacturer of your appliance can differ requiring special instructions STOP READ THE WARNINGS ABOVE If the appliance does not turn on ...

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