grounding for cathodic protection

[jdgnflorida]

I work for a water utility where we use rectifiers for cathodic protection for the main water pipeline. We use individual services (along a main roadway and bridges) to feed our rectifiers. We are using two ground rods that are six feet apart as our main grounding electrode as we do not want to affect the rectifier by grouding to the waterpipe. My question is what else can we use in accordance with the code to achieve 25 ohms or less rsistance to ground without interfference to the rectifiers as the ground rods are not working?

 

[Dennis Alwon]

What are you expecting the ground rods to accomplish?

 

[ActionDave]

@ Dennis- Are you thinking he is expecting the ground rods to prevent the water pipe from deteriorating? That is what it sounds like to me.

@ jdgnfloridathe- 25 ohms or less rule only applies to a single ground rod, so if that is what you are trying to avoid you could make your own Concrete Encased Electrode, but by the strict interpretation of the NEC you would still have to bond a metal water line present at the service.

 

[kwired]

@ Dennis- Are you thinking he is expecting the ground rods to prevent the water pipe from deteriorating? That is what it sounds like to me.

@ jdgnfloridathe- 25 ohms or less rule only applies to a single ground rod, so if that is what you are trying to avoid you could make your own Concrete Encased Electrode, but by the strict interpretation of the NEC you would still have to bond a metal water line present at the service.

I would guess the water line is not part of the building or structure containing his service equipment is one way to not have to bond to the water pipe. If this is just a post/pole with service and his cathodic protection equipment installed on it all he will likely have for grounding electrode in most cases is a ground rod - or two.

 

[don_resqcapt19]

You can't use the water line as a grounding electrode when it has cathodic protection. The code would only require the two ground rods in this application.

 

[tom baker]

You can install and use any of the electrodes listed in 250.52.

Personally I would just install two and call that good. However, if you are concerned about protecting your equipment from lightning, then your grounding system will be much more expensive and extensive.

 

[mike_kilroy]

I work for a water utility where we use rectifiers for cathodic protection for the main water pipeline. We use individual services (along a main roadway and bridges) to feed our rectifiers. We are using two ground rods that are six feet apart as our main grounding electrode as we do not want to affect the rectifier by grouding to the waterpipe. My question is what else can we use in accordance with the code to achieve 25 ohms or less rsistance to ground without interfference to the rectifiers as the ground rods are not working?

What does this mean? not enough current flow from the rectifiers? Pipe is corroding anyway? no voltage differential between the pipe or rectifiers and ground rods?