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Daneel 05-29-2011 09:24 PM

mixed neutral and ground
 
An old log cabin I am thinking of remodeling has no separate safety ground. Two ground electrodes (ground rod, well pipe) connect to neutrals at the meter base, in a junction box, and at the hot water heater.

Definitely not to code. If I isolate ground connections and connect them directly to the main panel, there may still be "joints" between neutral and ground that I haven't found. How unsafe is this and why?

Thanks,
Daneel

Jim Port 05-29-2011 09:30 PM

Grounding electrode conductors as well as equipment grounding conductors can be connected to the neutral buss in a service panel.

Are you asking about receptacles or panel connections?

Speedy Petey 05-29-2011 09:50 PM

Quote:

Originally Posted by Daneel (Post 657383)
An old log cabin I am thinking of remodeling has no separate safety ground. Two ground electrodes (ground rod, well pipe) connect to neutrals at the meter base, in a junction box, and at the hot water heater.

Definitely not to code. If I isolate ground connections and connect them directly to the main panel, there may still be "joints" between neutral and ground that I haven't found. How unsafe is this and why?

Thanks,
Daneel

As Jim states, this is perfectly normal and required.
This "joint" as you call it is the neutral/ground bond, or "main bonding jumper", and is what gives you the safety ground for circuits and feeders. This safety ground does NOT come from ground rods or other electrodes.

Daneel 05-30-2011 12:18 AM

mixed neutral and ground-clarification
 
I thought the safety ground "network" (including a ground rod and other grounding electrodes) was only supposed to be bonded to neutral at the main panel.

In this old house, these is no separate ground network. The ground rod connects to the meter base neutral and to neutral conductors (via a wire nut) in a junction box. One ungrounded duplex apparently was replaced with a grounded receptable and the ground is simply connected to the neutral conductor. A wire from the well pipe is also connected to the water heater frame and to neutrals in a nearby juction box (via a wire nut). I suspect there are other boxes where neutrals are bonded to box metal. In the main panel, some neutrals go to the a bar that bonds to the panel. One neutral is connected to panel itself -- so panel metal is part of the conducting path back to the PoCo neutral.

I propose to replace the main panel, connect the ground rod and well pipe only to the main panel, and to provide a separate safety ground to a few receptacles and main junction boxes -- until I get around to rewiring everything.

My question is how unsafe is the present hodge-podge of grounded neutrals and what can go wrong if some boxes (receptacles, lights) and conduits are bonded to neutrals?

Thanks,
Daneel

Speedy Petey 05-30-2011 08:23 AM

Quote:

Originally Posted by Daneel (Post 657465)
I thought the safety ground "network" (including a ground rod and other grounding electrodes) was only supposed to be bonded to neutral at the main panel.

Once again, the grounding electrode system has NOTHING to do with the "safety" equipment grounding conductors. They are two different systems that service two different purposes.



Quote:

Originally Posted by Daneel (Post 657465)
In this old house, these is no separate ground network. The ground rod connects to the meter base neutral and to neutral conductors (via a wire nut) in a junction box. One ungrounded duplex apparently was replaced with a grounded receptable and the ground is simply connected to the neutral conductor. A wire from the well pipe is also connected to the water heater frame and to neutrals in a nearby juction box (via a wire nut). I suspect there are other boxes where neutrals are bonded to box metal. In the main panel, some neutrals go to the a bar that bonds to the panel. One neutral is connected to panel itself -- so panel metal is part of the conducting path back to the PoCo neutral.

I sort of misread your first post. I now see what you are saying about the grounds being connected to neutrals outside the main panel and/or meter base. YES, all of that is BAD news, and should be corrected.




Quote:

Originally Posted by Daneel (Post 657465)
I propose to replace the main panel, connect the ground rod and well pipe only to the main panel, and to provide a separate safety ground to a few receptacles and main junction boxes -- until I get around to rewiring everything.

Good call. :thumbsup:



Quote:

Originally Posted by Daneel (Post 657465)
My question is how unsafe is the present hodge-podge of grounded neutrals and what can go wrong if some boxes (receptacles, lights) and conduits are bonded to neutrals?l

It is very unsafe if there is a fault or a compromised neutral somewhere. There is <almost> always current flowing on a neutral, so if it is connected to ground somewhere and the neutral is compromised then the grounding conductors and/or any exposed metal parts can and will become energized.

AllanJ 05-30-2011 07:19 PM

why am I gettting double posts when I try to edit?

AllanJ 05-30-2011 07:38 PM

For 100 amp or smaller service run a #6 copper ground wire non-stop from the first main disconnect breaker of switch's box where neutral and ground are tied together, to the ground rod. Run a #6 ground from the water pipe to the closest point on the former items.

For larger services run a #4 ground wire from the pipe to the panel (may be spliced) and a #6 non-stop from the ground rod to the panel.

Separate neutrals from grounds everywhere downstream of the main disconnect. You can temporarily run separate ground wires from selected receptacles to the panel or to the nearest point on one of the fat ground wires mentioned previously.

Ground fault circuit interrupters will work if the circuit or receptacles are not grounded.

Now if I were compelled to put in a new main disconnect upstream of, say at the meter, what had been my main disconnect, say the top breaker in my panel, then I would be mighty tempted to make no changes in the latter panel or the cable going to it, assuming I was not upgrading there.


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