Control System Monitoring - State Water Heaters 120 Series Service Handbook

control system monitoring

The Control System monitors the "state" of the pressure switch contacts individually through three separate
circuits, see Wiring diagram on page 44. The state of the switch refers to whether the switch contacts are open
or closed, see Construction & operation on page 28.
At the beginning of a heating sequence, before the Combustion Blower is energized, the Control System
enters the Input Verification operating state, see operating States on page 48. during Input Verification the
Control System monitors all three pressure switches to ensure their contacts are in the correct "normal"
state. The Blower Prover switch contacts must be open, the contacts for the Blocked Intake Air and Blocked
Exhaust switches must be closed, see Figure 30 on page 28 and the Sequence of operation on page 54.
If any of the pressure switch contacts are not in their correct normal state during Input Verification the Control
System will lock out and display a fault message on the LCd indicating which pressure switch caused the
fault condition, see Figure 31 below. If all system checks pass during the Input Verification operating state the
Control System enters the Pre-Purge operating state and energizes the Combustion Blower.
After the Combustion Blower is energized the Control System must confirm the Blower Prover switch contacts
have closed, see the Sequence of operation Flow Chart on page 55. The Blocked Intake Air and Blocked
Exhaust switch contacts must remain closed at all times.
If the Blower Prover switch contacts are closed during the Input Verification the Control System will lock out
and display Blower Prover Failure on the LCd. If the Blower Prover switch contacts do not close after the
Combustion Blower is energized the Control System will lock out and display Blower Prover Open on the
LCd. If either the Blocked Intake Air or Blocked Exhaust switch contacts open at any time during a heating
sequence the Control System will lock out and display Blocked Air Intake or Blocked Exhaust on the LCd.
See Figure 31 below.
Blower Prover Failure
Fault occurred 2 mins ago
The blower prover switch is
closed out of sequence.
Call a service professional:
Your Company Name Here
(press [DOWN] for more....)
CHANGE
Blocked Air Intake
Fault occurred 2 mins ago
The combustion air intake is
restricted.
Call a service professional:
Your Company Name Here
(press [DOWN] for more....)
CHANGE
PRESSURE SWITCH FAULT MESSAGES
BACK ADVANCED
BACK ADVANCED
Servicing should only be performed by a Qualified Service Agent
Blower Prover Open
The blower prover switch remains
open after the blower has been
energized.
Call a service professional:
Your Company Name Here
(press [DOWN] for more....)
CHANGE
Blocked Exhaust
The exhaust is blocked or
restricted. Ensure
condensate hose is draining.
Call a service professional:
Your Company Name Here
(press [DOWN] for more....)
CHANGE
Figure 31
Fault occurred 2 mins ago
BACK ADVANCED
Fault occurred 2 mins ago
BACK ADVANCED
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