XIII. Troubleshooting
WARNING
TURN OFF POWER TO BOILER BEFORE REPLACING FUSES OR WORKING ON WIRING.
A.Troubleshooting problems where no error code is displayed:
Table 13.1: No Error Code Displayed
CONDITION | POSSIBLE CAUSES | |
Display Blank, Fan off, LWCO lights off | • No 120VAC Power at boiler. Check breaker and wiring | |
between breaker panel and boiler | ||
| ||
| • Loose 120VAC connection wiring between boiler | |
Display Panel Blank, Fan running | MCBA | |
• Blown “F1” fuse in MCBA (see Figure 13.2 for location). | ||
| ||
| Replace with 5A fuse provided | |
| • Defective AT250 transformer | |
Display reads “U.125” continuously, Fan running | • Blown “F3” fuse in MCBA (see Figure 13.2 for location). | |
| Replace with 4A | |
Boiler not responding to call for heat, Status code on display | • Boiler is not seeing call for heat. Check thermostat or | |
zone wiring for loose connection, miswiring, or defective | ||
=”0” (see Figure 11.1) | ||
thermostat/zone control. | ||
| ||
Boiler fires, but display panel is blank | • Loose ribbon cable | |
• Defective display | ||
|
Figure 13.2: MBCA Fuse Location
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