Next Tech: Ground Loop/Lift

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Proformance

DJ Extraordinaire
Nov 6, 2006
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4,180
Update:

Did a basic test on the circuit to determine what level of sustained current load it is capable of carrying without failure. The purpose of the test is to determine if the circuit can meet or exceed the same sustained load capacity rating of the wire segment it replaces. So, far I have not been able to find it's failure point.

I installed the circuit directly inline on the live supply return (120V measured) and began the test immediately after soldering such that the components in the circuit were already heated to a point too hot to touch. I then increased the load in 100 watt (resistive) increments until the circuit was running a sustained 2400 watts, or 20 Amps. If you recall, that's 4 times higher then the published rating for the HumX.

Nothing in the circuit failed in that load range. It was able to carry a 20A sustained load and maintain a secure closed circuit.

I do not have a tester capable of determining if one or both diodes have retained current blocking properties below 500mV (Ground loop inhibitor.) 20A is precisely at the rectifiers rated limit - so, it depends on how conservative that rating is. The purpose of this test was simply to determine if the material structure of the assembly itself is at least as robust as the original rated wire segment.

At a later date I'll test it with 15A and 20A inductive loads, and then try a direct short, but my instinct at this point is that with respect to safety this is going to perform just as it should.

Whether or not it will be effective at inhibiting the kind of ground loop I'm targeting is still to be determined.
 

Proformance

DJ Extraordinaire
Nov 6, 2006
6,844
4,180
Should clarify, each time the load was increased the ENTIRE load was switched on from a zero state, so that any surge associated with switching or hot-plugging that we see in real life would be equally possible with every step of the test.

While these won't be used with inductive loads I'm going to do that test just for it's surge potential, i.e. I have radial arm saw with a 120V/240V motor and in 120V mode a cold start can often produce a surge that trips a breaker the moment you hit the switch..
 

Proformance

DJ Extraordinaire
Nov 6, 2006
6,844
4,180
Update: Success!
Did another test on this circuit today.

First, having previously tested it successfully with a 20A (resistive) continuous load , I was now able to verify that even after operating at that level, the circuit and it's diodes still retained their current blocking qualities in the minimal ground loop interrupting range. (Recall - this test installed it onto the live line load rather than the typically uncharged ground leg.)

Second, I tested the circuit in a dead short.condition. The test could best be described as: uneventful. The cold branch breaker tripped instantaneously while the entire assembly of diodes and resistor saw no visible damage and emitted no heat. The entire leg and assembly passed the short to the breaker equally as well as the original uninterrupted ground wire.

Third, after the dead short, the high current carrying capability of the circuit's diodes (as predicted) remained intact while their ground loop blocking qualities did not. Hence, the safety ground remains after a serious fault, but the diode's would need to be replaced if we still want it to perform the ground loop remedy.
 
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