Target Intelliground™ Reading: No Neutral-Ground Short. (NOTE: If all indicated lamps ‘blink’ every two seconds when performing this test, it is likely that the hot conductor at the outlet is loose!)
IMPORTANT: If the Intelliground™ indicates a NEUTRAL-GROUND SHORT, then it must be corrected before performing any other measurements with the tester.
Likely Cause For Incorrect Reading: The neutral conductor and the ground conductor are bonded together within 20’ (6m) of the outlet that is being tested.
NOTE: If the outlet being tested is within 20 feet (6m) of a Main Service Panelboard or Isolation Transformer, then the outlet is likely detecting the bond at either of those two locations.
Likely Solution: There may be many reasons why the outlet is wired improperly. Proceed with caution! Engage a qualified electrician to rewire the outlet so that there is no bond between neutral and ground.
Why Is It Important To Separate Neutral and Ground?
The National Electrical Code requires that the neutral and equipment grounding conductors only be bonded at the main service equipment and the source of a separately derived system (e.g., secondary winding of an isolation transformer). Bonding the neutral and the ground downstream from either of these two points would result in ac current flowing on the ground, which would elevate voltages on the frames of all equipment with respect to earth. The amount of voltage on the frame of equipment would be a product of the ac current and the equipment grounding conductor impedance.
As seen in the drawing below, an improper neutral-to-ground bond exists at the branch circuit panelboard. Some of the load current (10 amperes) splits at the improper neutral-ground bond and flows along the equipment grounding conductor path. The current traveling through the equipment grounding conductor’s impedance (1 ohm) produces a 5-volt drop on the frame of the panelboard and all equipment fed from it. This voltage will create a shock condition for personnel downstream from this point.
Another potential problem is the likelihood ac current could be imposed on bonding conductors within telecommunication spaces. This could further compromise the site characteristics and no amount of additional bonding will make the problems go away!