Dock shock

[readydave8]

From a conversation with acquaintance

Swimmers getting tingle from water to ladder

Electrician found 3 volt difference

HO said Electrician added ground rod at house (not dock) and problem went away

I feel like there is more to story. Is there a way that extra ground rod at house could have changed voltage reading between water and dock?

 

[don_resqcapt19]

In my opinion, the addition of the ground rod making the voltage go away is very unlikely. Something else is going on.

 

[hillbilly1]

Is this on Lake Rabun? Or is it further south on Lanier? Lanier has about 3 volts on it anywhere you go. I drove three rods on Nottely, and actually increased the voltage on the metal dock by a half volt. The lawyer that owned it rented the house and dock as a VRBO, and was worried about liability. He had me install this;

Dock Lifeguard | Products

Purchase Dock Lifeguard Products

www.docklifeguard.com

 

[readydave8]

This one is on Hartwell

Yeah I was thinking same thing that more ground rods might make it worse

Acquaintance (he's not a customer) confirmed that EC drove rod at house, not dock

Something else going on, probably never know what

 

[readydave8]

"Back Feed from your Home: If you have a well-grounded dock with a grounding rod < 25 ohms, but your "homes grounding rod is above the 25 ohm threshold, your electrical system my run into the situation where non-lethal stray electricity from your home (i.e. From a A/C Unit or Heat Pump) may bypass the home’s grounding rod and feed down to the grounding rod with lower resistance (The Dock) which is tied to your dock. To correct this situation you will need to correct the ground resistance of your home’s grounding rod, or you can run an isolated grounding rod to feed the Dock Lifeguard unit."

Huh.

 

[Little Bill]

"Back Feed from your Home: If you have a well-grounded dock with a grounding rod < 25 ohms, but your "homes grounding rod is above the 25 ohm threshold, your electrical system my run into the situation where non-lethal stray electricity from your home (i.e. From a A/C Unit or Heat Pump) may bypass the home’s grounding rod and feed down to the grounding rod with lower resistance (The Dock) which is tied to your dock. To correct this situation you will need to correct the ground resistance of your home’s grounding rod, or you can run an isolated grounding rod to feed the Dock Lifeguard unit."

Huh.

AI?

 

[readydave8]

AI?

It was from FAQ in advertising for product Hill Billy mentioned

 

[kwired]

It was from FAQ in advertising for product Hill Billy mentioned

Looking at the advertising seems this is mostly an alarm and not so much any automatic protector. It mentions (with no details) tripping a GFCI to turn power off at dock which does nothing to prevent EGC to earth voltages which are the major issue in most these situations.

 

[hillbilly1]

Looking at the advertising seems this is mostly an alarm and not so much any automatic protector. It mentions (with no details) tripping a GFCI to turn power off at dock which does nothing to prevent EGC to earth voltages which are the major issue in most these situations.

It will trip the gfi, if it gets to alarm status, but as you said, if the voltage is coming from elsewhere, it will not help as far as removing the voltage unless it is coming from that protected circuit. If I remember correctly, they had a resistor from the neutral to the ground in series with the alarm dry contact. Watch the installation videos, they say to drive ground rods until you get to 25 ohms! LOL!

 

[Fred B]

The potential for shock is very recognized thus the requirements found in article 555 of the NEC.
Article 555.1 indicates these requirements apply to both commercial docks as well as private docks for 1 or 2 family dwellings. Part of the requirements are for posting of signage as currently there is no way to prevent and ensure that a voltage variants won't be present. Source of these voltages are varied and can be anything from a local wiring issue to a neighbors system, to a utility system, to a fault from a boat on that dock or nearby.

555.10(3) The signs shall state “WARNING — POTENTIAL SHOCK HAZARD — ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER.”

Closest thing that can be done is to create an equipotential bond between the water, lake bottom and the dock with all the attached components. Easier said than done. The only problem with trying to "cure" the issue with bonding is the potential of bring in a charge that might not be present without the connection.

 

[LarryFine]

Faraday wet-suits?