Smith XWH 150 - Sequence of Operation

56
SEQUENCE OF OPERATION
OPERATION TOUCH SCREEN DISPLAY
1. The control will turn on the water heater pump (always
ON except in Setpoint Adjustment). The ow switch and/or
LWCO must close.
2. The control turns on power to the damper relay. The damper
proving switch, air pressure switch, and blocked drain switch
must close.
3. The control starts the prepurge cycle.
4. The control starts the trial for ignition by energizing the spark
electrode and opening the gas valve.
5. If ame is not detected after the sparking ends, the control
will perform a postpurge, then start another prepurge cycle
and try to light the burner again. On the 500 and larger
models, the control will lock out if this second attempt fails.
On the 400 and smaller models, the control will perform a
total of 4 attempts before locking out.
6. If ame is detected, it holds the ring rate steady for a few
seconds to let the ame stabilize, then it begins to modulate
the ring rate based on a set point or some other command
(such as a 0-10V BMS signal).
7. Once the call for heat is satised, the control will de-energize
the gas valve. The blower will continue to run during the
postpurge.
8. The water heater pump will continue to run for its respective
pump delay time before turning off. A 60 second anti-cycle
period will start, which will delay any new call for heat until
it times out.
9. In Standby, ready to start a new cycle.
Tank Temperature 90°F
Operating Setpoint 93°F
Status: Pre-Purge
HELPDISABLE
A. O. Smith XP
MENU
Tank Temperature 90°F
Operating Setpoint 93°F
Status: Ignition
HELPDISABLE
A. O. Smith XP
MENU
OFF
GAS
O
N
Tank Temperature 90°F
Operating Setpoint 93°F
Status: Post-Purge
HELPDISABLE
A. O. Smith XP
MENU
Tank Temperature 90°F
Operating Setpoint 93°F
Status: Heating
HELPDISABLE
A. O. Smith XP
MENU
OFF
GAS
O
N
Tank Temperature 92°F
Operating Setpoint 93°F
Status: Short Cycling
HELPDISABLE
A. O. Smith XP
MENU
Tank Temperature 92°F
Operating Setpoint 93°F
Status: Standby
HELPDISABLE
A. O. Smith XP
MENU
Tank Temperature 92°F
Operating Setpoint 93°F
Status: Standby
HELPDISABLE
A. O. Smith XP
MENU
Tank Temperature 92°F
Operating Setpoint 93°F
Status: Standby
HELPDISABLE
A. O. Smith XP
MENU
Tank Temperature 90°F
Operating Setpoint 93°F
Status: Post-Purge
HELPDISABLE
A. O. Smith XP
MENU