Riello Array AR 399 SE Installation, Operation And Service Manual page 56

APPENDIX
RECYCLING AND DISPOSAL APPENDIX
− Disconnect the multimeter and reconnect the wires, as
shown in the picture below.
−
1 (NC)
2 (NO)
Fig. 61 Wired pressure switch
− Test the pressure switch on the other side of the boiler
(module 4 or 8); repeat the process from Fig. 58 through
Fig. 61.
If the multimeter shows "0" (or any other symbol confirming the
electrical continuity between 1 (NC) and 3 (COM) of the air pressure
switch), the error on the boiler is due to a lack of water on the hy-
draulic circuit (or a failure of the pressure switch itself).
If the multimeter shows the air pressure switch circuit between 1
(NC) and 3 (COM) is open, the error is due to an air pressure differ-
ential between boiler cabinet and boiler room higher than 1.4"wc
(or a failure of the pressure switch itself).
The root cause is most likely an obstruction/blockage on combus-
tion air inlet.
3 (COM)
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