By Jeff Harrop
Ground is the earth and where voltages over 50 volts must be referenced from. This includes DC (Direct Current) and AC (alternating current) voltages. In order to do this we have a connection to the earth for each power system installed on a premise. It can be a set of driven rods, a plate, the copper water piping system, or a well casing.
The photovoltaic panels have lethal potential voltages and therefore must be bonded to the grounding system to protect people from live voltages from energizing the metal framework of the panels.
This is accomplished by attaching a copper wire to each panel. It can be multiple wires or just one. The arrangement of these, this bonding, must be continuous so that the removal of any panel does not break the bond to the other panels.
The size of this copper wire must be #8 AWG (American Wire Gauge) and be supported at intervals according to section 12 of the CEC (Canadian Electrical Code). When this bond is routed in a conduit or changes to a protected cable it can be reduced to the cable size that will now carry the bonding function.
The bond connection to the panel is very important. The anodized Aluminum frame of the panels must be electrically connected to the copper bond wire. To do this the anodized coating must be penetrated with a start washer or with a WEEB connector. There also needs to be anti-oxidizing pastes applied to the aluminum. If using a WEEB connector two must be in contact with each panel.
The connector that holds the bond wire must be waterproof, a stainless steel housing and screw work best for this application. The easiest type is a layin lug, that allows the bond wire to just lay in the connector and be attached with the stainless screw.
The bond wire continues until it connects to the proper terminal in the inverter as per manufacturer’s instructions.
The bond wire if spliced or connected at any location must be done so with UL listed connectors.