Katessa Harris
New User
In a house that is not new construction, is there a way to tell if it has been properly grounded?
correct grounding
- Thread starter Katessa Harris
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wbalsam1
Senior Member
- Location
- Upper Jay, NY
Katessa Harris said:
My suggestion is to have a skilled electrician make the call. Satisfy yourself to his/her credentials, first. :smile:
76nemo
Senior Member
- Location
- Ogdensburg, NY
No one else in the Local 134 can help you? Are you referring to local amendments:-?
- Location
- Illinois
- Occupation
- retired electrician
Look for the connections to the grounding electrodes that are required in 250.50 are there.
brian john
Senior Member
- Location
- Leesburg, VA
I visual inspection by a QUALIFIED electrician is the best way I can think of.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Katessa Harris said:
I would look for ground rods, which most won't have, water pipe bonding and proper bonding of any metal conduit that contain service conductors. I would also make sure the service panel is bonded properly and would check any subpanels to be sure they have separate bars for the grounding conductors.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
About all you can do is check and see if the proper sized grounding electrode conductor is attached to all the required grounding electrodes.
L
Lxnxjxhx
Guest
grounding
grounding
There are many previous posts on how to measure ground resistance. The specification limit seems to be < 25 ohms.
The instruments made for this purpose use frequencies other than 60 Hz, or multiples thereof, because there seems to be a lot of ground noise at various freqs. I think there are some favored, "quiet", freqs. commonly used.
This 60 Hz prohibition kind of puts a damper on homebrew ground testers.
You may want to read some of Fluke's online literature on this.
If they don't use DC, then ground impedance, Z, =E/I, where Z, E, and I are all vectors, not scalars. In principle the measurement is very straightforward, but there are probably many ins and outs when actually doing this. I wouldn't rule out a shock hazard.
Using a schematic (or wiring diagram which is not the same thing) of your service as a roadmap-of-sorts may prevent confusion as to where the current is actually going. If the current goes through your body then there usually is no confusion.
grounding
There are many previous posts on how to measure ground resistance. The specification limit seems to be < 25 ohms.
The instruments made for this purpose use frequencies other than 60 Hz, or multiples thereof, because there seems to be a lot of ground noise at various freqs. I think there are some favored, "quiet", freqs. commonly used.
This 60 Hz prohibition kind of puts a damper on homebrew ground testers.
You may want to read some of Fluke's online literature on this.
If they don't use DC, then ground impedance, Z, =E/I, where Z, E, and I are all vectors, not scalars. In principle the measurement is very straightforward, but there are probably many ins and outs when actually doing this. I wouldn't rule out a shock hazard.
Using a schematic (or wiring diagram which is not the same thing) of your service as a roadmap-of-sorts may prevent confusion as to where the current is actually going. If the current goes through your body then there usually is no confusion.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
there is no requirement that the ground resistance be any particular value in the code. as long as the required GE connections are present, its good as far as the code is concerned.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
The code does not have a maximum limit on the grounding resistance. What it says if a rod, pipe or plate electrode is more than 25 ohms an second electrode must be added. Then you go home.Lxnxjxhx said:
L
Lxnxjxhx
Guest
Philosophy question
Philosophy question
If the NEC is about safety, I'd think where it is reasonably practical to do so there'd be performance testing required. Is this wrong? Is testing of new work just "good practice?"
It doesn't seem to me that following proper procedures, even meticulously, always guarantees the desired result.
Philosophy question
If the NEC is about safety, I'd think where it is reasonably practical to do so there'd be performance testing required. Is this wrong? Is testing of new work just "good practice?"
It doesn't seem to me that following proper procedures, even meticulously, always guarantees the desired result.
stickboy1375
Senior Member
- Location
- Litchfield, CT
Lxnxjxhx said:
IMO, its terribely wrong and a waste of time.
- Location
- Illinois
- Occupation
- retired electrician
The connection to earth has very little to do with electrical safety in standard building wiring installations. 250.56 is the only place the 25 ohm rule showes up and it only applied to rod, pipe (driven pipe, not water pipe) and plate type electrodes. It only says that if you don't have 25 ohms or less with the first electrode you install a second. There is no requirement to try to get down to the 25 ohms.Lxnxjxhx said:
L
Lxnxjxhx
Guest
testing of new work, not just for grounding
testing of new work, not just for grounding
I finally figured out what bothers me about this.
If you follow The Code, you're covered, . . .right? OK, here's something from
http://en.wikipedia.org/wiki/Moral_hazard
"For example, an individual with insurance against automobile theft may be less vigilant about locking his car, because the negative consequences of automobile theft are (partially) borne by the insurance company."
I mentioned some guys who wired my screened porch in another post. Now, I recall that while the outlets did actually supply electricity the GF did not trip with a 60 mA fault from L to G. The test button did work because it connects an internal resistor.
If this was his own screened porch, would he have put a resistor or small lamp from hot to ground?
The inspector wrote this guy up from A to Z for other problems, but I didn't him using a test lamp either.
When there is a problem, how is the Hot Potato of Blame, the "due diligence" issue, handled? Does the NFPA assume liability?
testing of new work, not just for grounding
I finally figured out what bothers me about this.
If you follow The Code, you're covered, . . .right? OK, here's something from
http://en.wikipedia.org/wiki/Moral_hazard
"For example, an individual with insurance against automobile theft may be less vigilant about locking his car, because the negative consequences of automobile theft are (partially) borne by the insurance company."
I mentioned some guys who wired my screened porch in another post. Now, I recall that while the outlets did actually supply electricity the GF did not trip with a 60 mA fault from L to G. The test button did work because it connects an internal resistor.
If this was his own screened porch, would he have put a resistor or small lamp from hot to ground?
The inspector wrote this guy up from A to Z for other problems, but I didn't him using a test lamp either.
When there is a problem, how is the Hot Potato of Blame, the "due diligence" issue, handled? Does the NFPA assume liability?
- Location
- Illinois
- Occupation
- retired electrician
Not possible. If the GFCI trips with the internal test button it will trip with a 60mA external ground fault. All the internal resistor does is let some of the current flow on a path that is not sensed by the current sensor.Lxnxjxhx said:
brian john
Senior Member
- Location
- Leesburg, VA
If there are any grounding issues this is the least of your concerns. A complete visual inspection BY SOMEONE that knows what they are looking at is IMO the best solution.
Yes it is wrong, because the average electrician is not going to perform the test properly so the results are meaningless.
Do you perform earth ground resistance test?
Last edited:
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080427-1942 EST
The basic theory of a GFCI is a current transformer with a threshold detector on the current transformer output that trips a latch.
If you run the hot and neutral wires thru the current transformer in the correct direction, then if both currents are equal they balance each other and the current transformer output is zero. A resistive load on the current transformer output provides a voltage proportional to the unbalanced current. There are other ways to build the same device.
For some very useful information see
http://cache.national.com/ds/LM/LM1851.pdf
Notice the trip-time curve on p4, and a typical circuit figure 2 on p6. Note: the UL specification is rather long at 5 MA, about 5 seconds, and to get 1/2 cycle operation it is about 200 to 300 MA.
To cause an unbalanced current it is not necessary that the leakage be to ground. Any way that a sufficient unbalanced current can be introduced into either the hot or neutral conductor will cause the device to trip.
.
The basic theory of a GFCI is a current transformer with a threshold detector on the current transformer output that trips a latch.
If you run the hot and neutral wires thru the current transformer in the correct direction, then if both currents are equal they balance each other and the current transformer output is zero. A resistive load on the current transformer output provides a voltage proportional to the unbalanced current. There are other ways to build the same device.
For some very useful information see
http://cache.national.com/ds/LM/LM1851.pdf
Notice the trip-time curve on p4, and a typical circuit figure 2 on p6. Note: the UL specification is rather long at 5 MA, about 5 seconds, and to get 1/2 cycle operation it is about 200 to 300 MA.
To cause an unbalanced current it is not necessary that the leakage be to ground. Any way that a sufficient unbalanced current can be introduced into either the hot or neutral conductor will cause the device to trip.
.
L
Lxnxjxhx
Guest
. . .you perform earth ground resistance test?
. . .you perform earth ground resistance test?
No, but I did electronics work.
With equipment that had sensitive inputs driving several watts of power on the output we had to worry about single point grounds, but that was it.
We don't have the equivalent of the NEC, so I guess we did a lot more testing. At least I did.
. . .you perform earth ground resistance test?
No, but I did electronics work.
With equipment that had sensitive inputs driving several watts of power on the output we had to worry about single point grounds, but that was it.
We don't have the equivalent of the NEC, so I guess we did a lot more testing. At least I did.
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