Amp readings on ground rod ?

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acrwc10

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
On most houses there is some minor reading on the GEC at the rod, at least in my area, on an average .03 to .05. This is with the main breaker off. What have you seen as "normal" and have there been any conditions that added it, telco, CATV, etc.
I ask because today I was reading a .13 amp on a house with the main service off.
 
resistance

resistance

Senior Member
Location
WA
acrwc10 said:
On most houses there is some minor reading on the GEC at the rod, at least in my area, on an average .03 to .05. This is with the main breaker off. What have you seen as "normal" and have there been any conditions that added it, telco, CATV, etc.
I ask because today I was reading a .13 amp on a house with the main service off.
Click to expand...
My first question would be and is. Are you using an analog or digital meter?

May be a good idea to grab an analog meter (If you don't have one), and see if you can get a voltage reading. If you can, then get back to us, and we can discuss neutral to earth voltage.
 
acrwc10

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
Yes it is a digital meter ( Fluke 33 ) and I do understand the phantom voltage issue with digital Volt meters but have not heard of phantom Amp readings.
What would be the best way of checking for Voltage, both AC and DC on the bonding side of the telco, CATV, and through the ground rod, What scale would you be testing at to see if , for example, the telco had a bonding/grounding issue at the pole, that maybe following the service grounded conductor. Or if there is a bad POCO neutral buried underground that is putting minor current onto the system?

Just trying to get a better ideal of what these readings could mean, if anything.
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
Current on the grounding doesent excite me as much as voltage, most services will have current on the grounding because of all the parallel paths in the power supply system, and I have seen as high as 12-15 amps. but voltage to Earth was less then 1 volt, the reason I say this is because current on a low impedance path will not raise the voltage on the neutral like when you have a lost neutral, it is when we start seeing a voltage to a Earth referance point that raises my hairs, when I see a house with a pool or on a lake with a dock that has electric, and I see more then 1 volt, then its time to look closer, if I see 15-30 volts the utility gets called, and test are done to check for a lost MGN connection or lost primary neutral, and thats pool or no pool.
 
Rick Christopherson

Rick Christopherson

Senior Member
Jim W in Tampa said:
Come on Bob i know your smarter than that. Clamp ons are nothing more than a transformer and it reads volts calibrated in amps.
Click to expand...
No Jim, a clamp on meter does not measure voltage, at least not in the way you worded your first reply. The meter itself may be seeing voltage from the clamp-on probe, but the probe is registering current in the conductor, and communicating this information to the meter as a voltage (voltage for a digital meter, but current for an analog meter) . The process is actually the same regardless whether the meter was connected in series with the load, or clamp-on.
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
most meters will be most accurate in the center rang of there scale, digital has auto range but I have found most at current above 2 or 3 amps can be very close, and think of it this way, since GFCIs also measure in the same way it would seem they would have to be very accurate, they just don't trip went the coil sees a voltage, it trips when it sees 5-6ma's I have 4 ranges on my Amp-Probe 400a AC 600 AC 400 DC and 600 DC each one specked by the manufacture to have less then a 2% error in the selected range.
 
A/A Fuel GTX

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
acrwc10 said:
On most houses there is some minor reading on the GEC at the rod, at least in my area, on an average .03 to .05. This is with the main breaker off. What have you seen as "normal" and have there been any conditions that added it, telco, CATV, etc.
I ask because today I was reading a .13 amp on a house with the main service off.
Click to expand...

Bad neutral terminations on services coming from the same transformer are likely contributors to this.....
 
Jim W in Tampa

Jim W in Tampa

Senior Member
Location
Tampa Florida
Rick Christopherson said:
No Jim, a clamp on meter does not measure voltage, at least not in the way you worded your first reply. The meter itself may be seeing voltage from the clamp-on probe, but the probe is registering current in the conductor, and communicating this information to the meter as a voltage (voltage for a digital meter, but current for an analog meter) . The process is actually the same regardless whether the meter was connected in series with the load, or clamp-on.
Click to expand...

The meter itself is reading voltage and calibrated in amps based on amount of current. Without volts you have nothing.
 
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