gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110505-1512 EDT
You need quantitative data of the present conditions that can be consistently measured. That is slab to water voltage.
Then you could experiment in a small area with maybe two rods 4 feet apart driven under the slab. These would be connected to the EGC and see what effect this has on your previous test measurement in this localized area. For experimentation ground rod material would be convenient.
What is the ultimate solution? I do not know. Your groove, cable, and back fill might work, but the NEC, etc. experts need to advise on what must be done. If you can get the cement to water to be near zero volts, then what is the remaining potential gradient from the slab to the earth as you walk from the slab to the earth? What is near zero volts needs to be defined. My guess is under 500 millivolts.
Also you might need a filter that selects only 60 Hz at the meter input to minimize measurement error from higher frequency sources, such as close high power broadcast stations.
.
You need quantitative data of the present conditions that can be consistently measured. That is slab to water voltage.
Then you could experiment in a small area with maybe two rods 4 feet apart driven under the slab. These would be connected to the EGC and see what effect this has on your previous test measurement in this localized area. For experimentation ground rod material would be convenient.
What is the ultimate solution? I do not know. Your groove, cable, and back fill might work, but the NEC, etc. experts need to advise on what must be done. If you can get the cement to water to be near zero volts, then what is the remaining potential gradient from the slab to the earth as you walk from the slab to the earth? What is near zero volts needs to be defined. My guess is under 500 millivolts.
Also you might need a filter that selects only 60 Hz at the meter input to minimize measurement error from higher frequency sources, such as close high power broadcast stations.
.