A.O. Smith BTX-100 Service Handbook page 32

ULTRA HIGH EFFICIENCY POWER VENT/POWER DIRECT VENT - SERVICE MANUAL
UIM (CONT)
Table 5 - Operational States (Modes)
STATE
Standby
Input Verification
Pre-Purge
Igniter Warmup
Ignition Activation
Ignition Verification Assurance of proper flame sense is being determined.
Inter-Purge
Heating
Post-Purge
Fault
Technical Literature Department
The water heater is not in an active heating cycle. This usually means the temperature
in the tank has reached Operating Set Point and has not dropped low enough to initiate
a call for heat.
The control system is waiting for specific conditions to occur (primarily pressure switch
normal state verification - see page 20) before the unit can continue in the Sequence of
Operation.
The blower has been energized - the control system is purging out any excess gas or
left over products of combustion from the heat exchanger at the beginning of each
heating cycle.
The igniter has been energized and is currently warming up to ensure proper ignition -
typically last 17-20 seconds.
The control system is allowing for a steady burner flame to be established. Duration of
this and the Ignition Verification state is typically 4-6 seconds.
After a failed trial for ignition the control system is purging out any excess gas or left
over products of combustion from the heat exchanger before another trail for ignition.
Burner flame has been properly established - minimum flame sensing current has
been verified by the control system - water in the tank is being heated.
The control system is purging out any excess gas or left over products of combustion
from the heat exchanger after a successful heating cycle.
The control system has detected a fault and declared a fault condition. The control
system is locked out. A fault message is displayed on the UIM (page 27). The problem
that caused the lock out must be corrected before the water heater can resume a
heating cycle.
Servicing should only be performed by a Qualified Service Agent
DESCRIPTION
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