grounding cold water pipe ?????

[stewdish]

hey guys a stupid question as i came up as a electrician in the navy so my theory of grounding is a little different on the ocean. anyway i understand driving a electrode for grounding and if there no electrode we can use the cold water pipe within 5 feet of entrance. but in layman terms why the cold water pipe and what is the theory of this as i am reading the nec and just NOT getting it.
hot tubs have to be grounded to the cold water pipe as well right. why and theory please.,


thanks stew

 

[Dennis Alwon]

hey guys a stupid question as i came up as a electrician in the navy so my theory of grounding is a little different on the ocean. anyway i understand driving a electrode for grounding and if there no electrode we can use the cold water pipe within 5 feet of entrance. but in layman terms why the cold water pipe and what is the theory of this as i am reading the nec and just NOT getting it.
hot tubs have to be grounded to the cold water pipe as well right. why and theory please.,
thanks stew

First off your question is not stupid-- my answer may be but not your question.:grin:

If the water pipe is in direct contact with the earth for 10 feet then it is an electrode and must be used. If there is plastic coming into the house and then copper water lines in the house then you must bond the water lines.

Ground rods are still necessary unless you use a CEE as described in art.250.53((A)(3). Yo should read art. 250. Section III-- it is hard to understand at times but it may help.

I will leave the "WHYS" to the engineers so they can get technical with you-- they love to do that so I'll let them play. :grin:

Tubs need to be bonded to the water lines if the tub is connected to a metal piping system. I will not go there as this has been argued forever.

 

[charlie]

Stew, the overall reason for bonding is to prevent a difference in potential between items that a person can touch and complete a circuit. Additionally, the bonding together of metallic stuff is also to provide a return for fault current to the source to operate overcurrent devices.

The overall reason for grounding is to provide a path for lightning and other sources of higher voltage such as a primary to secondary fault in a transformer.

Without going into a lot of detail, that is pretty much the reason for all of the rules in Article 250. By the way, a book can be written on the stuff I left out . . . OH . . . several already have been written.

 

[quogueelectric]

Stew, the overall reason for bonding is to prevent a difference in potential between items that a person can touch and complete a circuit. Additionally, the bonding together of metallic stuff is also to provide a return for fault current to the source to operate overcurrent devices.

The overall reason for grounding is to provide a path for lightning and other sources of higher voltage such as a primary to secondary fault in a transformer.

Without going into a lot of detail, that is pretty much the reason for all of the rules in Article 250. By the way, a book can be written on the stuff I left out . . . OH . . . several already have been written.

Why are there so many people who think grounding things are more dangerous than not??

 

[charlie]

Why are there so many people who think grounding things are more dangerous than not??

And you could write another book on that subject. :smile:

 

[augie47]

stew, using the cold water pipe goes back to early codes. You have to distinguish "bonding" the pipe for equal potential and using it for a grounding electrode. Back when I was a pup, the entire city water piping system was metallic and you could probably get no better ground that that miles of piping.
With the advent of PVC piping, the usefullness of the cold water pipe as a grounding elctrode diminished and we soon had the requirement to supplement it with another grounding means such as a ground rod.
Undeground piping is still useful as an grounding elctrode and interior piping must be bonded to prevent shock potential.