120V circuit to detached garage in conduit from load side panel in house.
My 61-165 indicated an open ground (and a correct ground everywhere else I tested inside the house), when further investigation by others indicated a correct ground I went back and retested with my 61-058, which indicated a correct ground.
If you are not sure about a circuit being open ground, you can plug in your tester, then use a voltage indicator on the face plate screw to see if it lights up.
If the circuit is grounded, the indicator will not light up. It it isn’t grounded the indicator will light up.
You should have one of these indictors to test for reverse polarity on open ground and 2-prong receptacles (the smaller slot should be hot, and the other one is not)
I recommend the fluke indicator. The CG el-cheapo’s are next to worthless IMHO.
The SureTest has this built into the unit. You can check the resistance of all three conductors up to 3.0 ohms. If your reading is >3, you can be sure the ground is no good, or not present.
A “normal” reading is generally in the range of 0.25 ohms. A reading of 1.0 or greater is too high for the EGC, and may show as an “open-ground” on the initial test cycle of the SureTest.
FWIW - If you test the ground impedance on a circuit that is GFCI protected, the GFCI will (should) trip.
Jeff/Paul, wasn’t there a discussion a couple of years ago about a false open ground with an outlet, typically in the garage, that is directly out of the panel box, or am I making this up?
I don’t recall that particular discussion Dave, however, there have been several discussions regarding “false-ground” readings with the SureTest.
Basically, the SureTest gives this indication when the resistance is to low between the ground (egc) and the neutral (grounded conductor).
It’s common to get this indication when the receptacle is close to the service equipment (where the grounds and neutrals are bonded) or near a distribution panel where the neutrals have been grounded (which we know to be improper).
The indicator is intended to help the inspector identify “bootleg” grounds, where the egc has been “grounded” to the circuit-neutral, rather than grounded at the panel.