Dueling Suretests

[Michael D. Thomas]

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.

Defective 165, or ????

[Jeffrey R. Pope]

The 61-165 is more "sensitive" than others. Many times it will show an "open-ground" condition, when the contact/connection is poor.

Next time, check the ground impedance when you get this reading.

[Ralph Brady]

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.


Like this:

[Michael D. Thomas]

OK, bear with me a bit, I clearly don't understand this as well as I should, and if I don't probably a lot of others don't either.

Jeffery,

Across what two points should I measure the impedance, and what should I expect to find?

Ralph,

What result should I expect from your test technique?

Thanks

[Ralph Brady]

Originally Posted by mthomas2

Ralph,

What result should I expect from your test technique?

Thanks

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.

[Paul W. Abernathy]

Originally Posted by mthomas2

OK, bear with me a bit, I clearly don't understand this as well as I should, and if I don't probably a lot of others don't either.

Jeffery,

Across what two points should I measure the impedance, and what should I expect to find?

Ralph,

What result should I expect from your test technique?

Thanks

I think Jeff means using the SureTest to check that as it has this setting built in.

[Jeffrey R. Pope]

Originally Posted by pabernathy

I think Jeff means using the SureTest to check that as it has this setting built in.

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.

[Dave Bush]

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?

[Jeffrey R. Pope]

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.

[Patrick Bolliger]

Probably loose conduit at a fitting or corrosion at a fitting. Cuz you know EMT is perfect...Right Paul

[Paul W. Abernathy]

lol....Gotta love those Chicago EMT Lovers....lol

[Michael D. Thomas]

Thanks for the information.

[Bob Elliott]

Originally Posted by pabernathy

lol....Gotta love those Chicago EMT Lovers....lol

It belongs in metal conduit the way G-D intended.

Romex is glorified extension cord.(I am sure Edison and Tesla would agree ,if they had not both died touching Romex).