Shock from Water

[jmellc]

Went to check out situation at a camp the other day. People getting shocked in the showers. We are replacing the service, which is very old and shabby.

I found a bad neutral, 69 volts to phase A and 174 to phase B. No ground wire from the panel feeding bath house. Neutral grounded to ground rods and water main. I think the missing neutral causes the water main to be energized.

Anyone seen similar situations?

 

[ptonsparky]

Went to check out situation at a camp the other day. People getting shocked in the showers. We are replacing the service, which is very old and shabby.

I found a bad neutral, 69 volts to phase A and 174 to phase B. No ground wire from the panel feeding bath house. Neutral grounded to ground rods and water main. I think the missing neutral causes the water main to be energized.

Anyone seen similar situations?

Sounds like you have it under control.:thumbsup:

 

[kwired]

at the voltages you mentioned and assuming nominal 120/240 system, your water pipe and ground rods are at about 50 volts above earth. They are still 120 to the source neutral but you have some voltage drop (and with an open neutral a very severe drop) between the source and your point of measurement.

Even if you didn't have an open neutral you would still see some voltage here but would be limited to whatever the voltage drop on the neutral conductor actually is.

 

[domnic]

at the voltages you mentioned and assuming nominal 120/240 system, your water pipe and ground rods are at about 50 volts above earth. They are still 120 to the source neutral but you have some voltage drop (and with an open neutral a very severe drop) between the source and your point of measurement.

Even if you didn't have an open neutral you would still see some voltage here but would be limited to whatever the voltage drop on the neutral conductor actually is.

HOW do you know their about 50 volts above earth with not knowing what is on in the bath house ?

 

[kwired]

HOW do you know their about 50 volts above earth with not knowing what is on in the bath house ?

Both lines are 50 volts (approximately) off in relation to this "remote neutral" then they are to the actual supply neutral that is grounded at the source. One is 50 volts high the other 50 volts low. Both still add up to the applied 240 line to line though you just have a remote neutral that is 50 volts off from the true neutral which is at ground potential. If you draw the circuit out and apply Kirchoff's voltage laws you will have a 240 volt source, one load with a 70 volt drop across it, the lost neutral point, another load with a 170 volt drop across it. The lost neutral point is going to be 50 volts different from the grounded neutral at the source. There will be high resistance path(s) back to the grounded neutral at the source via any grounding electodes present at the remote building that will throw those measurements off a little, but it will still be pretty close if OP is measuring 70 and 170ish volts.

Change the balance of the 120 volt loads and that figure will change. Get the loads so they are very near balanced and the water/water piping will be at very near zero volts from ground and the shock incidents will go away, until it is unbalanced enough to be noticeable again. Some people will have different tolerance levels and will begin to feel it at different levels.

 

[domnic]

Both lines are 50 volts (approximately) off in relation to this "remote neutral" then they are to the actual supply neutral that is grounded at the source. One is 50 volts high the other 50 volts low. Both still add up to the applied 240 line to line though you just have a remote neutral that is 50 volts off from the true neutral which is at ground potential. If you draw the circuit out and apply Kirchoff's voltage laws you will have a 240 volt source, one load with a 70 volt drop across it, the lost neutral point, another load with a 170 volt drop across it. The lost neutral point is going to be 50 volts different from the grounded neutral at the source. There will be high resistance path(s) back to the grounded neutral at the source via any grounding electodes present at the remote building that will throw those measurements off a little, but it will still be pretty close if OP is measuring 70 and 170ish volts.

Change the balance of the 120 volt loads and that figure will change. Get the loads so they are very near balanced and the water/water piping will be at very near zero volts from ground and the shock incidents will go away, until it is unbalanced enough to be noticeable again. Some people will have different tolerance levels and will begin to feel it at different levels.

If the GEC was open also what would happen then ?

 

[GoldDigger]

If the GEC was open also what would happen then ?

Nothing would change assuming that there are not any line to EGC faults present at the same time. And a two-pole GFCI would not detect any fault current, since the open neutral only affects line and neutral current.

 

[kwired]

If the GEC was open also what would happen then ?

The grounding electrode(s) already have a relatively high resistance, if they had low resistance they would carry the imbalance and we might not everknow the neutral is open.

Now if you lost the neutral to earth bond at the source that would change your ground reference, if the end of the line we are discussing has the only ground reference then the voltages from neutral to earth will be pretty minimal in the vicinity but if on top of that you still lost the (now not grounded) neutral conductor back to the source you would still have varying voltages between L1, L2 and the "local" N depending on load conditions at time of measurement.

 

[brantmacga]

Oh yeh ....

I went on a bachelor party excursion a few years ago, and we rented these small cabins on the St Johns River in Florida.

The first night, I came in knee-walking drunk and attempted a shower. I remember grabbing the shower head and then thinking I was dead; my god it hurt. Woke up some time later face down in the shower. Thankfully their drains were working properly.

I told the lady at the bait shop/check in desk the next morning about it and she shrugged it off. Someone probably died already.


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