Blower Operation Error; Pressure Switches; Control System Monitoring - State Water Heaters 60120-100250 Service Handbook

2. BLOWER OPERATION ERROR

Blower Operation Error
Fault occurred 2 mins ago
Blower Prover Pressure Switch may
have failed closed. Check/replace
pressure switch.
Call a service professional:
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CHANGE
CHECK/ REPAIR:
• This switch is normally open and is used to prove blower operation. This switch should be open when
blower is not running. Check continuity of pressure switch. See "Pressure Switch Tests" section on Page
12 thru Page 15.

PRESSURE SWITCHES

The water heaters covered in this Service Handbook are factory equipped with four pressure switches
(including the Low Gas Pressure Switch). "Top View" Figures on Page 5 shows the location of the three
pressures switches on top of the water heater. This section of the Service Handbook covers pressure switch
construction, operation and the test procedures used to diagnose operational problems associated with
pressure switches. The pressure switches are identified with colored labels; Blower Prover Switch is Green,
Blocked Air Intake Switch is Blue, & Blocked Exhaust Switch is Red.

CONTROL SYSTEM MONITORING

The Control System monitors the "state" of the pressure switch contacts individually through three separate
circuits, see "Wiring Diagrams" on Page 52 & Page 53. The state of the switch refers to whether the switch
contacts are open or closed.
At the beginning of a heating sequence, before the Combustion Blower is energized, the Control System
enters the Input Verification operating state. 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 Air Intake Switch and Blocked Exhaust Switches must be closed.
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 UIM indicating which pressure switch caused the
fault condition. 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. The Heater Status Screen and
functionality of the water heater can be used for troubleshooting.
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 6. The Blocked Air Intake Switch 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 UIM. 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
UIM. If either the Blocked Air Intake Switch 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 UIM. Wires connecting to air switches are labeled near the terminals. Ensure no mis-wiring among
terminals.
BACK ADVANCED
Servicing should only be performed by a Qualified Service Technician
CAUSES:
• The Blower Prover Pressure Switch was detected
closed before blower operation.
11