Does anyone know exactly how the SureTest knows that there is “No Ground” on a circuit? I see this a lot actually and it is sometimes intermittent for example I check the receptacle a second time and there is no indication of no ground. Now if I am on a non-GFCI circuit I test the ground impedance and if is showing greater than 3 ohms. I know the general rule of thumb is less then 1 ohm to protect people and less than .25 ohms to protect equipment.
Is it simply a continuity test to the panel that should be strapped and bonded? In other words by checking continuity between ground and neutral? That does not trip the GFCI but the impedance test does?
I really want to fully understand this. I check voltage drops on my inspections and tag the outlets or “receptacles” of the specific value if >5%. I comment on the <10% drops with a generic explanation of voltage drops, what is and is not required and why they are important, and the ones >10% get a different comment about safety issues when high power demand is made on a lower voltage circuit increasing the current and heat in the wire. I am starting to bring in grounds to the fold and marking those also with a green sticker indicating a ground failure. Often times these are circuits with surge protectors being used and IMO having no ground or a high impedance ground, will negate the ability of a surge protection device to do it’s job. My thought is that often times what the SureTest is getting a high impedance ground and calling it “no-ground” which…might as well be the same right?
Yeah that is a frustrating one. I have ran into that a few times and it was on dead outlets. Or better explained as outlets I thought were dead. I do not believe it is the cable though in the case of the ground issues I see. I believe I will also carry one of the small little receptacle testers and see if it also gets a “No Ground”.
A high impedance ground is basically a no ground. You need a low impedance path to trip a breaker. A high impedance path may light up a plug in tester since they require very little power, however a dead short circuit may never clear the breaker placing 120 volts on all grounded equipment connected to that circuit.
What is the wiring method used btw? BX is notorious for having a High impedance as well as DIY grounding screw ups.
Yep, totally agree. And the same can be said about surge protection. I’m just wondering how the 61-164 or 165 decides that no ground exists. And it could be more aptly described as insufficient ground ( which is just as bad as no ground ). Maybe for example the connection on the ground is very poor. There is a ground albeit with high impedance. Now I am wanting to know what are the actual impedance numbers on the other receptacles on the same branch? Maybe it is possible that every ground in the whole house has higher impedance than the hot and neutrals, and the actual issue is at the rod, uffer, bonding, strapping or other reason at the main panel. Possibly the others do not fail for ground but are none the less inadequate really if they are an ohm or more.
If I know exactly how the instrument works, it changes my perspective on the nature of the issue at hand. It may be beyond the scope I understand but… I just like to know things for certain.
Keep in mind that the UFER, ground rod and water bond have nothing to do with clearing a fault. The fault is cleared via the low impedance path provided by the main bonding jumper (or that the equipment grounds are on the neutral bar) But either way the service neutral is what open the breaker.
Common reasons for high ground readings are BX cable (which has no bonding strip) and DIY screw ups.
What you are doing is far from being beyond scope. Its actually essential and mandated by electricians in many parts of the world. A high resistance ground can electrocute or start a fire. Using BX as an example, the jacket will pass current, but it may not be enough to open the breaker. When this happens, the BX armor will heat up like a heating elements and possibly start a fire.
Ah OK thanks for the feedback on the BX cable. I’m going to learn what I can about that and its prevalence of use here in the N. Texas area. The next house I get with a lot of “No Ground” indicators on the 15A non-GFCI circuits, I am going to then check the ground impedance on each receptacle to look at the pattern, If it is consistently the case that the impedance on the ground is greater than that of the hot or neutral, then that is where I start to conclude that the issue is at the service panel and therefore common to all the circuits. Also will keep the same idea in mind with the individual branch circuits. BTW they become quite obvious where they start and end when you are looking at voltage drops. I know it is beyond the scope to for example find a branch that by itself has multiple “no ground” indications, and then simply tighten that lug on the bus bar and see the problem go away. But then ask yourself OK if they all had grounds (technically) then apparently there is a threshold of acceptable. And if that is the case then also how does the device know without sending a current over the ground conductor? I assume it cannot be doing that because it would pop GFCI outlets just like doing the impedance test on a receptacle in a GFCI protected circuit.
It’s just how my mind works. I feel the need to know how the tool works to understand how to read the results.
The funny thing is often times I can never get my brain to make sense of it until I see it in a schematic. Like the whole strapping and bonding difference between main panels and sub panels. Only after I see the circuit in a schematic does it make sense.