John Wood Commercial - 300-400K BTU - Manual (Page 54)

54
seQuence of operation
read the Sequence of Operation below before attempting to
correct any operational problems. refer to the Features And
Components section beginning on page 7 for the location
of various water heater components described below. See the
Sequence Of Operation Flow Chart on page 55 also.
1. When the control system is first powered, during boot
up, it 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 low gas
pressure, 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 Hot Surface Igniter for
the igniter warm-up period.
7. The control system monitors the igniter current and must
sense a minimum of 2.0 AC amps for AJWSH130 300
100/101 Series and AJWSH130 400 101 series only, and
3.1 AC amps for AJWSH130 400 104 series.
8. If igniter amperage is confirmed at or above the required
minimum the control system energizes the 24 VAC gas
Valve allowing gas to flow to the Main burner.
9. The control system de-energizes the Hot Surface Igniter.
10. 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.
11. 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 VAC gas Valve and
enter the post-purge cycle (approximately 30 seconds).
12. 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.
13. 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.
troubleshooting
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. See
Clearances on page 11.
2. Ensure the area is free of corrosive elements and flammable
materials. See the instructions on page16.
Venting
3. Ensure the intake air and/or vent (exhaust) piping is the correct
size for the installed length. See Venting requirements on
page 21.
4. Ensure the maximum equivalent feet of pipe has not been
exceeded for the intake air and/or vent pipe. See Table 6 on
page 21.
5. Ensure the maximum number of elbows has not been
exceeded in the intake air and/or vent pipe. See Venting
requirements on page 21.
6. Ensure the balance plate and intake air screen are removed
from the intake air connection on the water heater when
installing the water heater in a Direct Vent configuration. See
Figure 17 on page 23.
7. Ensure all exterior clearances for the intake air, vent and
concentric terminations are maintained. See Vertical
Termination Installation on page 23, Sidewall Termination
Installation on page 25 and Concentric Termination
Installation on page 26. These clearances and those cited
by local and national codes must be maintained.
gas supply and piping
8. Ensure a supply gas regulator has been installed for each
water heater. See the requirements for a Supply gas
regulator on page 13 and Supply gas regulator on page
13.
9. Ensure the supply gas line to each water heater meets
the minimum supply gas line size requirements. See the
requirements for the Supply gas Line on page 13 and the
installation instructions on page 36 and 37.
condensate drain
10. 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. See Figure 9 on
page 16 and Condensate Drain Installation on page 35.
electrical connections
11. Ensure the power supply connections to the water heater
are polarity correct. See the requirements for the Power
Supply on page 13 and Electrical Wiring on page 38.
12. 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.