K8MHZ
Senior Member
- Occupation
- Electrician
'Not necessary' is not the same as 'maximum allowed'.
Indian electrical code.
- Thread starter ActionDave
- Start date
- Status
'Not necessary' is not the same as 'maximum allowed'.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
So. The NEC does not have a "maximum allowed" EGC either. I could run a 250kcmil for a 15A circuit.
- Occupation
- Licensed Electrician
Yes, I was. I couldn't see anybody making a rule for a maximum sized EGC allowed.
K8MHZ
Senior Member
- Occupation
- Electrician
I'm not the one that said either had a maximum allowed. TM said the Indian Electrical Code had a maximum size allowed, not me. I looked through the (copyrighted) code book he posted a link to and found no limits on the maximum size of an ECG.
Last edited:
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
My bad. I missed that in the OP.:ashamed1::slaphead:
Some day I will learn to read closer, but I guess this ain't it.
K8MHZ
Senior Member
- Occupation
- Electrician
My bad. I missed that in the OP.:ashamed1::slaphead:
Some day I will learn to read closer, but I guess this ain't it.
Wet noodle lashes to you!!!
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Wet noodle lashes to you!!!
Agreed.:weeping:
kwired
Electron manager
- Location
- NE Nebraska
True, might explain why that mess is there. If it were copper someone would likely have stripped it away. That or most of it is 18-2 lamp cord and not enough copper to be worth messing with it. Although there has to be a significant amount there anyway even if most of it is lamp cord.
T
T.M.Haja Sahib
Guest
But there is a conflict between the two codes. The Indian code permits not to increase the copper earth conductor beyond 100 sq.mm size, whereas the U.S code does not. That is the point here. Isn't it ?
kwired
Electron manager
- Location
- NE Nebraska
I think you are talking about maximum size of grounding electrode conductor. There is no such thing in NEC. There is minimum size required but you can always use a larger size.
Table 250.66 only lists the size of 3/0 (which 100 mm? falls between 3/0 and 4/0 AWG) as the largest minimum size grounding electrode conductor ever needed. Nowhere does it say it is the maximum size allowed.
T
T.M.Haja Sahib
Guest
So, it means this:
Per US NEC, it is not necessary to use copper ground conductor of size beyond 3/0. (no matter what the conductor size is).
Per Indian NEC, it is not necessary to use copper ground conductor of size beyond 100 Sq.mm. (no matter what the conductor size is).
K8MHZ
Senior Member
- Occupation
- Electrician
Just to clarify, per US NEC, it is not necessary to us any larger than a 3/0 CU for a Grounding Electrode Conductor. That does NOT apply to an Equipment Grounding Conductor. The size of the EGC is determined by table 250.122. Table 250.122 only goes to an OCPD setting of 6000 amperes, which requires an 800 kcmil EGC.
kwired
Electron manager
- Location
- NE Nebraska
Other than the equipment grounding conductor that K8MHZ brought up, Yes - where are you going with this?
100 mm? is between 3/0 and 4/0 AWG so requirement is nearly the same with both codes.
T
T.M.Haja Sahib
Guest
Even if GEC were accidentally cut in a grounding system per US NEC, protection for short circuit is still available through EGC still connected to the neutral. But if the earthing conductor in a grounding system per Indian NEC were cut, protection for short circuit is lost. So on this basis, I think providing a upper limit for minimum size copper conductor as 100 sq.mm per Indian NEC does not seem to be correct.
kwired
Electron manager
- Location
- NE Nebraska
I do not know Indian code.
In NEC, GEC is not intended to carry short circuit current. Your likelihood of ever having one able to carry enough current to allow for operation of an overcurrent device is not that great either. Exception would be a metal water pipe electrode that also has GEC attached to it at other services - this is because the primary fault current path would return to the source via the water pipe and then through the grounded service conductor at the other service. If the only path back to the source is through the earth even 1 ohm of resistance is not necessarily low enough to be reliable for the purpose of operating an overcurrent device. It will open smaller sized devices but not on magnetic trip features - it will take time to operate the overload feature.
If you are in an area where there is not much lightning, even though against the NEC requirements you can do just fine without a grounding electrode most of the time. Even if there is frequent lightning I have seen many places with no grounding electrode, doesn't mean it would be a little better installation with one, but often they just sit there doing very little, and a misapplied electrode creates more problems than it solves.
So what does the GEC do then? I thought it was to open "a" over current device. Though I've never understood how exactly, because it seemed to me it would open the circuit on the utility lines. For example, when the short to ground was in the service riser.
I take it, from your comment, that the Equipment grounding conductor is sized to open the over current device, but not the GEC?
Thanks
Mike
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
(2008)250.4A1 said:
After 40+ years in the business I still don't know what a "line surge" is. I also don't know how driving a ground rod will "limit the voltage to ground".(2008)250.4A2 said:
I don't think us Americans have this grounding thing figured out yet.
ice
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Un-documented, un-proven, personal opinion:
The ten bazillion driven ground rods in the US provide the utilities with a free ground grid. And that is something they can use.
ice
K8MHZ
Senior Member
- Occupation
- Electrician
As for line surges, I got to wire a $450,000 log home because its predecessor was burnt to the ground by a line surge.
What happened was (this from POCO engineers) a couple lines got crossed in a windstorm, fully saturating a transformer. When the lines came back apart, the transformer 'outrushed', surging the voltage on the lines for a few cycles. Enough to turn a night light into a fire. From there the fire spread to the curtains and shortly thereafter the entire log home was engulfed and destroyed.
The ground rods, obviously, were of no help. The new home is now outfitted with whole house surge protection.
As for Americans not having this grounding thing figured out yet, I have to agree. I get to see grounding from a different perspective than most, being a ham radio operator and all.
I can tell you that there are many myths about grounding that refuse to die. I can also tell you that most people can't explain the difference between bonding and grounding.
It's funny you bring up 'limit the voltage to ground'. I just had a conversation about that. If you read the entire passage, the reason for grounding is to limit the voltage between the ground and normally non-current carrying materials, such as metal enclosures and raceways.
While a rod or two will provide some limitation, they are poor choices for grounding electrodes. You have to realize that the NEC is a bare minimum. It's perfectly fine to use a more effective means of 'limiting', which is actually an attempt at equipotentiality.
- Status