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"?
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Yes
Set room thermostat lO°above room temperature.
Set boiler 10° (or more) above current
water temperature. Boiler turns on?
/No ___
Check for 12BY at LIX, L2X.
Check for 24V at R C
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on L7148.
BoilerShort terminalsstarts?
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No
÷
Turn power "ON".
Check all wiring connections.
Replace transformer as appropriate.
Thermostat cr Thermostat widng problem.
Check system per instructions provided with thermostat.
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Two Blinks:
Check sensor connections. If good, replace sensor.
L7148F Diagnostic LED, flashing?
Check:
| Yes | _ | Internal error, | replace L71 48F control. |
| Three or four | blinks: | ||
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| Check for 24V, | at | 81, B2? | I | |||
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| Check: |
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| Yes |
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| L7148F in reset mode (wait 5 minutes |
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| for control to | reset). |
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Check Circulator Pump, running? |
| Vent damper | apen? |
| L7148F is OK, | check ignition and gas |
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| valve system as described in literature | ||||||
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Yes |
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| Check vent damper cable and | I_ | t |
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| ts it still set |
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| connections. |
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| Check room | thermostat, | at | |||
| I | Replace vent | damper cable or damper |
| 10° above current | room | temperature? |
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Boiler shuts off at high limit setting? | I | as appropriate. |
| 7' |
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No | I | 120vacatC1,C27 |
| L | No | |
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Boiler shuts off above high limit setting? | L7148F | is OK |
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Check | other | system components: | ||||
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| Circulators, | Zone Valves | |||
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No (Below | HL) | Check: |
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4, |
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| Temperature/Pressure | gauge | ||||
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| accuracy |
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Check L7148F diagnostic | LED Flashing? | Sensor fully inserted | into well | |||
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| Thermo Well in good condition. | ||||
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| Thermo Well located per boiler OEM | ||||
| recommendations. |
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_tNo
Replace L7148F.
Control failure, incapable of self diagnostics.
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IReset thermostat and repeat voltage check
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4, |
| Yes |
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Check: |
| Two blinks, replace | sensor, |
Temperature/Pressure | gauge accuracy. | L_ Three or four blinks, | replace control. |
Thermo Well tocated per boiler OEM instructions.
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