Honeywell WT8840 User Manual

WT8840 TRADE WATER HEATER CONTROLS

WARNING

CAUTION

WARNING

WARNING

Perform Gas Leak Test

Fire or Explosion Hazard.
Can cause severe injury, death or property
damage.

Check for gas leaks with soap and water
solution any time work is done on a gas system.

Water Damage Hazard.
Can damage electrical components in the
WT8840.

Do not spray soap and water solution on the
WT8840 housing. Do not use an excessive
amount of soap and water to perform the gas
leak test.

Gas Leak Test

1. Paint pipe connections upstream of the water

heater control with a rich soap and water
solution. Bubbles indicate a gas leak.

2. If a leak is detected, tighten the pipe connection.

3.

Stand clear of the burner while lighting to prevent
injury caused from hidden leaks that could cause
flashback in the appliance burner compartment.

4. With the burner in operation, paint the pipe

joints (including adapters) and the control inlet
and outlet with a rich soap and water solution.

5. If another leak is detected, tighten the adapter

screw, joints, and pipe connections.

6. Replace the part(s) if a leak cannot be stopped.

Check the gas input and burner
flow rate

Fire or Explosion Hazard.
Can cause severe injury, death or property
damage.

Follow these warnings exactly:

1. Do not exceed input rating stamped on
appliance nameplate or manufacturer
recommended burner orifice pressure for
size of orifice(s) used. Follow instructions of
appliance manufacturer.

2. IF CHECKING GAS INPUT BY CLOCKING
GAS METER: Make certain there is no gas
flow through the meter other than to the
appliance being checked. Other appliances
must remain off with the pilots extinguished
(or that consumption must be deducted
from the meter reading). Convert flow rate to
Btuh as described in form number 70-2602,
Gas Controls Handbook, and compare to
Btuh input rating on appliance nameplate.

3. IF CHECKING GAS INPUT WITH
MANOMETER: Make sure the manual gas
shutoff switch is in the OFF position before
removing outlet pressure tap plug to connect
the manometer (pressure gauge). Also, move
the manual gas shutoff switch to the OFF
position when removing the gauge and
replacing the plug. Also shut off gas supply
before disconnecting manometer and
replacing plug. Repeat Gas 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 outlet pressure tap on the
water heater control. See Fig. 5.

MAINTENANCE

Fire or Explosion Hazard. Can cause severe
injury, death or property damage.

Do not attempt to take apart or clean the gas
valve inside the WT8840 control. Improper
cleaning or reassembly can cause gas leakage.

The maintenance program should include regular
checkout of the control as outlined in the Startup and
Checkout section, and the control system as described
in the appliance manufacturer literature.

Maintenance frequency must be determined individually
for each application. Some considerations are:

1. Cycling frequency. Appliances that may cycle

10,000 times annually should be checked
monthly.

2. Intermittent use. Appliances that are used

seasonally should be checked before shutdown
and again before the next use.

3. Consequence of unexpected shutdown. Where

the cost of an unexpected shutdown would be
high, the system should be checked more often.

4. Dusty, wet or corrosive environment. Since these

environments can cause the control to
deteriorate more rapidly, the system should be
checked more often.

The system should be replaced if:

• It does not perform properly on checkout or
troubleshooting.

• The control is likely to have operated for more
than 150,000 cycles.

• The control is wet or looks as if it has been wet.

TROUBLESHOOTING

Troubleshooting With Status
Indicator Assistance

1. Pilot burner must be lit. If not, push and hold

Pilot knob and light pilot with piezo. Error code
will be displayed when thermopile heats up.
Error code can be recognized by counting the
number of flashes of the status indicator after a
three second pause. One single flash (with set
point knob in PILOT position) indicates that the
control is in normal operation.

2. Observe status indicator on control; check and

repair the system as noted in Table 3 on page 6.
Flash codes are displayed with a three-second
delay between cycles. A continuous solid light
indicates system shutdown when knob is turned
from a temperature setting to OFF position.
When the solid light is present, the pilot and

5 34-00013EF—03

WT8840 TRADE WATER HEATER CONTROLS

main valve will not hold. When the status
indicator goes out, the user can restart the
system. (Approximate shutdown time is one
minute.)

3. After status indicator analysis and appliance

repair is complete, turn device knob to OFF, wait
until the indicator goes out, then perform
lighting procedure.

4. Status indicator light should be in normal mode

(1 flash) with the knob in the PILOT position.
Turn the device knob past the water temperature
in the tank should turn on the main burner. The
Status indicator light will strobe every three
seconds when there is a call for heat.

5. In the event of multiple failure codes, the next

failure code follows the previous failure code by
approximately three seconds with higher flash
count first.

Table 3. Troubleshooting with status light visual indication.

LED

Error

**

Normal
operation.
No action
required.

Action
required.

Code

1 flash
every 3
seconds

Strobe
every 3
seconds

2 flashes Low thermopile

4 flashes Temperature cut-out

5 flashes Water temperature

6 flashes Tank leakage

Number of LED Flashes*Detected Failure Recommended Action

Not an error;
indicates the
electronics is holding
the Pilot Valve open
and the Main Valve
closed.

Not an error;
indicates call for heat
during normal
operation, Main valve
open.

voltage; main valve
not turned ON.

limit reached.

sensor failure.

detected by
accessory module.

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).

None.

Check thermopile and its
connections. Check pilot flame.

Check the valves and the water
temperature sensor. Reduce the
water temperature setpoint.
Thoroughly check out main valve
operation and water temperature
control before walking away.

Check water temperature sensor
and its connection for open
circuits, shorts, or differences in
resistance between the two sensor
elements.

Control recovers after receiving
message from accessory module.

7 flashes Electronics Failure Replace control module.
8 flashes This is just a warning;

Solid ON Not an error—

*

LED Error Codes are flashed once per second, with a three-second pause between repeating the error code.

**

Maximum two different errors can be displayed simultaneously if more than one error has been detected.

The control does not
see power decaying
with the knob in the
OFF position.

indicates that the
control is in OFF
mode.

Check valves.

None; wait until LED turns off if you
want to restart the system.

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