John Wood Envirosense Power Direct Vent (May 2010 or later) - Manuel (Page 51)

51
TROUBLESHOOTING
SEQUENCE OF OPERATION
Read the Sequence of Operation below before attempting to
correct any operational problems. See the Sequence Of Operation
Flow Chart.
1. When the control system is first powered, during boot up, the
blower will run momentarily and stop, and the control system
will display water heater model information during initialization.
After a few moments the control system LCD which is part of
the UIM (user interface module) will display the default screen
known as the Desktop screen.
2. If the control system determines that the actual water temperature
inside the tank is below the programmed Operating Set Point
minus the Differential setting, a heating cycle is activated.
3. The control system then performs selected diagnostic system
checks. This includes confirming the blocked exhaust, blocked
intake and ECO (energy cut out) switch contacts are closed.
The Blower Prover Switch contacts are confirmed open.
4. If all diagnostic checks are successfully passed, the control
system energizes the Combustion Blower for pre-purge.
5. The control system must confirm the Blower Prover Switch
contacts close after the Combustion Blower is energized.
6. If the Blower Prover Switch contacts are confirmed closed the
control system energizes the spark igniter.
7. After a few seconds, the control system energizes the 24V Gas
Control Valve allowing gas to flow to the Main Burner.
8. The control system de-energizes the spark igniter.
9. The control system monitors the flame sensor to confirm a flame
is present at the Main Burner. If a flame is not verified during the
ignition trial period the control system will try for ignition up to
two more times. If flame can not be verified after three trials for
ignition, the control system will lock out and display the Ignition
Failure Fault message.
10. If a flame is verified, the control system will enter the heating
mode where it will continue heating the water until the Operating
Set Point is reached. At this point, the control system will de-
energize the 24 V Gas Control Valve and enter the post-purge
cycle (60 seconds).
11. The Combustion Blower will run for the duration of the post-
purge cycle to purge the water heater of all combustion gases.
When the post-purge cycle is complete, the blower is de-
energized and will coast to a stop.
12. The control system now enters the standby mode while
continuing to monitor the internal storage tank water temperature
and the state of other system devices. If the tank temperature
drops below the Operating Set Point minus the Differential
setting, the control will automatically return to Step 2 and repeat
the operating cycle.
INSTALLATION CHECKLIST
The list below represents some of the most critical installation
requirements that, when overlooked, often result in operational
problems, down time and needless parts replacement. This is not
a complete list. Before performing any troubleshooting procedures
use the list below to check for installation errors. Costs to correct
installation errors are not covered under the limited warranty.
Ensure all installation requirements and instructions in this manual
have been maintained and followed.
WATER HEATER LOCATION
1. Ensure proper clearances to combustibles are maintained and
there is sufficient room to service the water heater.
2. Ensure the area is free of corrosive elements and flammable
materials.
VENTING
3. Ensure the intake air and/or vent (exhaust) piping is the correct
size for the installed length.
4. Ensure the maximum equivalent feet of pipe has not been
exceeded for the intake air and/or vent pipe.
5. Ensure the maximum number of elbows has not been exceeded
in the intake air and/or vent pipe.
6. Ensure all exterior clearances for the intake air, vent and
concentric terminations are maintained. These clearances and
those cited by local and national codes must be maintained.
7. If venting direct vent, ensure the screen located in air intake at
the water heater was removed.
GAS SUPPLY AND PIPING
8. Ensure the supply gas line to each water heater meets the
minimum supply gas line size requirements.
CONDENSATE DRAIN
9. Ensure the condensate drain is properly connected to the
exhaust elbow on the water heater with a water trap to prevent
vent gases from escaping into the installed space and draining
freely to a suitable floor drain.
ELECTRICAL CONNECTIONS
10. Ensure the water heater is properly grounded. Flame sensing
requires an adequate earth ground. If the water heater is not
properly grounded it will cause Ignition Failure.