Service equipment neutral to ground

Status
Not open for further replies.
cppoly said:
Just curious, if the neutral buss bar is connected to the ground buss bar at service equipment, then wouldn't neutral current flow through the service enclosure as a return path back to the utility source?
Click to expand...

I have a little bit of a different take on it. Now as others have said, even with no common metal water pipes connected back to the transformer thru other services, and just a rod or two, you will have some current getting back to the source via dirt. That isnt really what the OP was asking or questioning. Note that the GEC is required to connect to the neutral conductor or its buss. I dont see current generally flowing through the service enclosure/cabinet unless something is not done correctly. I suppose where you have a separate EGC and neutral bus and metal frames of utilization equipment are sitting on dirt/concrete or connected to metal water pipes, you would then have a very small amount of current flowing through the cabinet.
 
electrofelon said:
I have a little bit of a different take on it. Now as others have said, even with no common metal water pipes connected back to the transformer thru other services, and just a rod or two, you will have some current getting back to the source via dirt. That isnt really what the OP was asking or questioning. Note that the GEC is required to connect to the neutral conductor or its buss. I dont see current generally flowing through the service enclosure/cabinet unless something is not done correctly. I suppose where you have a separate EGC and neutral bus and metal frames of utilization equipment are sitting on dirt/concrete or connected to metal water pipes, you would then have a very small amount of current flowing through the cabinet.
Click to expand...
The most common scenario for current "through" the enclosure is when there is metal conduit between the service disconnecting means enclosure and the meter can
 
cppoly said:
So if there is neutral current flowing through service equipment enclosures, 10A, 20A, 100A, etc... this isn't harmful if someone touches the equipment?
Click to expand...
Totally depends on the impedance of the current path back to the source. There will be a voltage drop on any conductor but keeping that minimal only gives minimal rise in voltage when measured between the point you are interested in (service enclosure in this case) and the ground potential objects within reach of a potential shock victim.

mwm1752 said:
The current does not flow to the grounding electrode in earth as a path
Click to expand...

mwm1752 said:
the flow goes back to the source & earth is not a source -- the same reason the electrode will not trip a breaker -- show me a diagram of your thoughts -- simply if there is a current flow & your break the connection/ tap the buss & you will see an arc occurs. now take you electrode conductor & do the same thing/ no arcs -- now we can get into the resistance differentials & path continuity & really have conversation.
Click to expand...
Others already responded - but current takes ever path available. More impedance there is in a particlular path the less current flows in that individual path though. Typical grounded service conductor of just a ohm or two at the most carries nearly all the current, but even then at least a few milliamps is probably finding a way back through grounding electrode(s), earth and additional electrode(s) at the POCO infrastructure.

Earth is a pretty good conductor, but it is hard to make a low impedance connection to it. POCO has thousands of electrodes just in a local distribution area all bonded to their MGN making a pretty low impedance to earth on their end. But a single electrode at some customer building is still going to introduce quite a bit of resistance if you want to use the electrode only as a return path from a load to the source.
 
Status
Not open for further replies.
Top