H3C Technologies H3C WX5000 Series Access Controllers - Manual (Page 75)

B-2
3) Pay adequate attention if the red LED is on. You should correctly locate the problem, whether it is
caused because the ground cable of the arrester is not well grounded or because the live and zero
wires are connected in reverse direction.
4) You may use a multimeter to examine the polarity at the power receptacle of the arrester:
z With the power receptacle facing you, if the multimeter displays that the left wire is the zero wire
and the right is the live wire, it means that the PE terminal of the arrester is not well grounded.
z Otherwise, it means that the power receptacle of the arrester is set to the reverse polarity. In this
case, open the power receptacle of the arrester and correct the polarity. After that, if the red LED
still alarms, it means that the arrester is not well grounded yet.