Troubleshooting Guide : Heater - Schwank STS-JZ Installation & Owner's Manual

24. TROUBLESHOOTING GUIDE — HEATER OPERATION — FENWAL DSI
WARNING
SEQUENCE OF EVENTS (also see Fenwal DSI Control Troubleshooting previous page)
APPLY 120 VOLTS - GREEN LIGHT IS ON
SET THERMOSTAT TO CALL FOR HEAT
COMBUSTION AIR BLOWER STARTS
YES
AIR PROVING SWITCH HAS CLOSED.
CONFIRM 24 VOLTS PRESENT AT
"PSW" TERMINAL ON DSI CONTROL.
YES
BLOCKED FLUE SWITCH IS CLOSED.
CONFIRM 24 VOLTS PRESENT AT
"TH" TERMINAL ON DSI CONTROL.
AMBER LIGHT IS ON
YES
CONTINUED
Improper adjustment, alteration, service or maintenance can
cause property damage, injury or death. This heater must be
installed and serviced only by a trained gas service technician
• REMEDY ELECTRICAL SUPPLY FAULT
NO
• 120V BUT NO GREEN LIGHT --> REPLACE
GREEN LIGHT
FENWAL DSI CONTROL CHECKS THAT AIR PROV-
NO
ING SWITCH IS "OPEN" PRIOR TO POWER TO
BLOWER:
• USE OHM METER TO CONFIRM AIR PROVING
SWITCH IS "OPEN" :
• OHM METER READS "0" = SWITCH IS CLOSED
• REPLACE FAULTY PROVING AIR SWITCH
• OHM METER READS "1" = SWITCH IS OPEN
• CHECK 120V (±10%) TO FENWAL DSI AT "L1"
• CHECK 120V OUT "IND" TERMINAL TO BLOWER
YES
• FAULTY RELAY SWITCH IN DSI — REPLACE DSI
NO
• USE OHM METER TO CONFIRM INTEGRITY OF
BLOWER MOTOR WINDINGS
• REPLACE DEFECTIVE BLOWER ASSEMBLY
• CHECK TUBING TO AIR PROVING SWITCH IS
NO
CONNECTED AND NOT BLOCKED OR KINKED
• CHECK AIR PRESSURE WITH MANOMETER
• CHECK FOR OBSTRUCTION IN THE AIR INTAKE
• CHECK INTEGRITY OF SWITCH
• CHECK TUBING TO SWITCH IS CONNECTED
NO
AND NOT BLOCKED OR KINKED
• CHECK TUBE STATIC PRESSURE WITH MA-
NOMETER
• CHECK INTEGRITY OF SWITCH
• CHECK FOR AND REMEDY ANY OBSTRUCTION
IN THE VENT / TUBE
• 24V IS PRESENT AT "TH" TERMINAL, BUT NO
AMBER LIGHT ... REPLACE AMBER LIGHT
47
• REPLACE DEFECTIVE BLOWER
• REPLACE DEFECTIVE SWITCH
• REPLACE DEFECTIVE SWITCH
STS-JZ-F / IQ-F I&O Manual Z83.20-2016
IM101220
RD: APR 2019
RL: 20C