Sequence Of Operation - Smith XWH 150 Instruction Manual

SEQUENCE OF OPERATION

OPERATION
1. The control will turn on the water heater pump (always
ON except in Setpoint Adjustment). The flow 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 flame 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 flame is detected, it holds the firing rate steady for a few
seconds to let the flame stabilize, then it begins to modulate
the firing rate based on a set point or some other command
(such as a 0-10V BMS signal).
7. Once the call for heat is satisfied, 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.
TOUCH SCREEN DISPLAY
Tank Temperature
Operating Setpoint
S t a t u s : S t a n d b y
MENU
Tank Temperature
Operating Setpoint
S t a t u s : S t a n d b y
MENU
Tank Temperature
Operating Setpoint
Status: Pre-Purge
MENU
Tank Temperature
Operating Setpoint
Status: Ignition
MENU
Tank Temperature
Operating Setpoint
S t a t u s : P o s t - P u r g e
MENU
Tank Temperature
Operating Setpoint
S t a t u s : H e a t i n g
MENU
Tank Temperature
Operating Setpoint
S t a t u s : P o s t - P u r g e
MENU
Tank Temperature
Operating Setpoint
S t a t u s : S h o r t C y c l i n g
MENU
Tank Temperature
Operating Setpoint
S t a t u s : S t a n d b y
MENU
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A. O. Smith XP
92°F
93°F
DISABLE HELP
A. O. Smith XP
92°F
93°F
DISABLE HELP
A. O. Smith XP
90°F
93°F
DISABLE HELP
A. O. Smith XP
90°F
93°F
OFF
O
GAS
N
DISABLE HELP
A. O. Smith XP
90°F
93°F
DISABLE HELP
A. O. Smith XP
90°F
93°F
OFF
O
GAS
N
DISABLE HELP
A. O. Smith XP
90°F
93°F
DISABLE HELP
A. O. Smith XP
92°F
93°F
DISABLE HELP
A. O. Smith XP
92°F
93°F
DISABLE HELP