@tonywinga ,
I was hoping you would respond to my above post in response to yours.
My post, 10/21/2021 9:03am.
It’s not often to read a post where someone with your back ground, can backup their findings with actual hands on testing with measurements.
I don’t doubt for a second what your test engineer suggested driving the ground solved the problem you were having. But do you know for sure why it did?
1) How old is the building? The reason I ask as a building ages the soil under a concrete slab, floor, that is on poured on grade will dry out.
2) What is the length of the ground rod that is driven into the earth through the drilled hole in the concrete floor? 8ft? Less?
3) By chance was the rod to soil resistivity, resistance, checked using the proper type of test equipment? If tested what did it measure? Less than 5 ohms?
If not tested the rod to soil resistance could actually be high. If the resistance is high then basically it would be no different than floating the chassis of the piece of test equipment above ground. Or at the very least equal to a resistor, resistance, in series with the test equipment and earth connection...By chance did the test engineer repeat the same test with the ground rod ground wire lifted from the piece of test equipment? (Floating the test equipment chassis above ground.)
4) If the test equipment is made to be used on airplanes I can’t help but wonder why you are not using a medical grade type Isolation transformer for a power source for the testing equipment.
One thing I have learned over the years about branch circuit wiring is the type of wiring used and the wiring method used for installation can make a difference on how well a circuit will perform.
A true dedicated circuit should not share the same raceway, conduit, or cable assembly with other branch circuits. Installing more than one branch circuit in the same conduit can/will cause induced voltage, as well as noise, from one current carrying circuit conductors to the other. Also when an insulated EGC is pulled in the conduit the current carrying circuit conductors can induce a voltage, and noise, onto the insulated EGC. This is true even for a dedicated circuit installed in a dedicated conduit where the hot, neutral, and insulated EGC are installed loosely, randomly, in the conduit. Twisting the current carrying conductors together and installing the EGC just along side the twisted current carrying conductors in the conduit greatly reduces the induced voltage onto the EGC.
Well worth reading.
2012 Seminar w-Notes v1-0.ppt - indy-aes-2012-seminar-w-notes-v1-0.pdf
Note page 16 and read pages 31 thru 36.
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FWIW: A test of a dedicated ground rod not bonded, connected, to the electrical service main system ground. (Grounding Electrode System).
A while back I drove a 5/8" x 8’ ground rod in the rock garden at the back of the house to use as a dedicated test grounding electrode. The driven ground rod is probably a good 70’ straight as the crow fly s, from the electrical service’s three 10’ each driven ground rods. I did a quick check measurement today and the difference of potential, voltage, from the test ground rod to the electrical service grounding electrode system measured 347mV. ( Meter, Fluke 87 mulimeter).
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