XIV. Troubleshooting

WARNING

Turn off power to boiler before replacing fuses or working on wiring.

A.Troubleshooting problems where no error code is displayed:

TABLE 14.1: 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 J-Box and MCBA

Display Panel Blank, Fan running

• 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 slow-

 

blow fuse provided

Boiler not responding to call for heat, Status code on

• Boiler is not seeing call for heat. Check thermostat or zone wiring for loose

display =”0” (see Figure 11.1)

connection, miswiring, or defective thermostat/zone control.

Boiler fires, but display panel is blank

• Loose ribbon cable

• Defective display

 

Figure 14.2: MBCA Fuse Location

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