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HONEYWELL L7148F TROUBLE SHOOTING GUIDE
Start
Boiler is cold.
Boiler is not reaching proper temperature
or will not tum on.
4,
Check:
L7t 48F Diagnostic LED =ON"?
I
Yes
Set room thermostat lO°above room
/
temperature.
Set boiler 10° (or more) above current
water temperature.
Boiler turns on?
Yes
i
Check Circulator Pump, running?
I
Yes
I
Boiler shuts off at high limit setting? I
No
!
Boiler shuts off above high limit setting?
t
No (Below HL)
4,
Check L7148F diagnostic LED Flashing?
I
No
4,
Check:
Temperature/Pressure gauge accuracy.
Thermo Well tocated per boiler OEM
instructions.
-- No--
]
No
Check for 12BY at LIX,
L2X.
Check for 24V at R C
I
___ Short terminals W-R (T-TW) ___
on L7148.
No Boiler starts?
I
No
÷
Check: _-_
L7148F Diagnostic LED, flashing?
I
No
÷
Check:
L7148F in reset mode (wait 5 minutes
for control to reset).
Vent damper apen?
Turn power "ON".
Check all wiring connections.
Replace transformer as appropriate.
Thermostat cr Thermostat widng problem.
Check system per instructions provided
with thermostat.
Two Blinks:
replace sensor.
Check sensor connections. If good,
_ Three or four blinks:
Yes Internal error, replace L7148F control.
I
Check for 24V, at 81, B2? I
I
J ,
-- Yes
4,
L7148F is OK, check ignition and gas
valve system as described in literature
provided with those products
t
No
Check vent damper cable and I_ t
connections.
Replace vent damper cable or damper
as appropriate.
_r
I 120vacatC1,C27 L
/
i
Y_s
4,
L7148F is OK
Check other system components:
Circulators, Zone Valves
Check:
Temperature/Pressure gauge
accuracy
Sensor fully inserted into well
Thermo Well in good condition.
Thermo Well located per boiler OEM
recommendations.
No
Yes
Yes
L_
Check room thermostat, ts it still set at
10° above current room temperature?
7'
Yes
_t No
Two blinks, replace sensor,
Three or four blinks, replace control.
Replace L7148F.
Control failure, incapable of self
diagnostics.
_r
I Reset thermostat and repeat voltage check I
i
I
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