Dunkirk Excelsior EXB Series Supplemental Instructions page 13

Figure 13 - Riello Wiring Diagram With Post Purge Timer And Blocked Flue Pressure Switch
Safety
WIRING DIAGRAMS
If a neutral or ground lead is attached to terminal 4, the CONTROL BOX
on the burner will be damaged should lockout occur.
13
P/N 240009355, Rev. C [11/15/2015]