mixed neutral and ground

Daneel said:

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

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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 said:

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.

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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.

Daneel said:

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.

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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.

Daneel said:

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.

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Good call. :thumbsup:

Daneel said:

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

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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.