Yesterday we were inquired to explain the importance of an SPD installation. This was because the contractor wanted to install the SPD at a lead length of approximately 10 feet. The effects of this would be devastating, we explain since the rule of thumb is that you increment 15 to 25 volts for every inch of cable you leave in the installation of an SPD. We explain that the closest an SPD is to the source or incoming bus bar the better and that installing the SPD, that far away from the service entrance would defeat the purpose of having an SPD in the first place to protect them from transients voltages or currents.
Installation is essential with these type of power quality products. You will have to refer to recommendations on the IEEE green and emerald books, for further information. Lead lengths cable is one cause of poor performing SPD’s and you can not blame the manufacturer of the product for this installation mishap.