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L7124U UNIVERSAL OIL ELECTRONIC AQUASTAT® CONTROLLER
TROUBLESHOOTING
When attempting to diagnose system performance,
references to the LED can help to identify specific areas
not working properly. The LED are:
PWR—ON indicates 24 Vac power present.
C—ON indicates circulator relay energized.
TSTAT—ON indicates thermostat call for heat.
ZC—ON indicates power to zoning.
B—ON indicates burner relay energized.
LL/DSBL—
System Condition
Boiler is cold, house is cold.
Boiler is hot, house is cold.
69-1232—2
Table 4. Corrective Action .
Check
PWR LED Off
PWR LED On
TSTAT LED Off
PWR LED On
TSTAT LED On
B (burner) LED On
PWR LED On
TSTAT LED On
LL/DSBL LED Flashing
PWR LED On
TSTAT LED On
C (circulator) LED On
PWR LED On
TSTAT LED On
C (circulator), ZC (zone circulator)
LED Off
PWR LED On
TSTAT LED On
ZC LED on
• ON indicates Low Limit function selected.
• OFF indicates Low Limit disabled.
• Flashing indicates error. See Table 3 and
Troubleshooting Guide, Table 4.
Table 3. LED Error Codes.
Number
of Blinks
2
Sensor Error (Open or shorted sensor.)
3
System error(s); e.g., setpoint POT failure.
4
Safety relay has welded, device requires
replacement.
.
Check:
— 120 Vac system power.
— 1A fuse on L7124U.
Check:
— Thermostat
— Thermostat wiring
— Check:
— 120 Vac B1-B2.
— If no, replace burner relay.
— If yes, check burner and wiring.
Refer to LED diagnostics, Table 3.
Check:
— 120 Vac, C1-C2.
— If no, replace circulator relay.
— Check for circulation, air entrap-
— If yes, check circulator and wiring.
— Check for circulation, air entrap-
Check:
— Boiler below low limit temperature,
Check:
— Boiler above low limit.
— If yes, check for 120 Vac between
— If no, replace ZC relay .
— If yes, check switch relays, zone
6
Cause
Corrective Action
ment, water flow.
ment, water flow.
wait for boiler to above low limit
temperature.
ZC and L2.
circulators and wiring.
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