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View Full Version : Grounding Issue with PG&E



garnell22
04-01-2009, 09:53 PM
Hi All

Have a question I'm hoping someone can help with. Recently had the house rewired. Had an early morning wake-up call from the Pacific Gas and Electric SWAT team today saying that I'm sending current down their gas line!

They came in and saw that the house has been grounded to the gas pipe from the street just before it goes into the meter. After the ground connects to the gas pipe it continues to a new ground rod. I also have a connection on the main water pipe again with a ground rod. Apparently you need 2 grounds to keep San Francisco inspectors happy?

The PG&E guy told me I have to move the ground connection to the other side of the meter so it is on the pipe coming out of the meter feeding the house rather than on the main feed going into the meter. They say the meter acts as a breaker so this is fine for them (i.e. won't be sending anything down the gas main).

This all leads me to ask several questions

How the heck did PG&E know I had a ground on the pipe (what were their sensors picking up?)
If the meter does really act as a breaker then surely that would defeat the point of me attaching the ground to the gas pipe coming out of the meter (i.e. it wouldn’t be grounded?!). In fact why are the grounds connected to the gas pipe and water pipe at all if they both run to ground rods?!


Thanks!!!

jimbo
04-02-2009, 07:16 AM
You need a well qualified electrician to sort this out.


As I understand it , you problem may revolve around this situation:

The gas pipe needs to be BONDED TO the grounding system. This prevents the gas pipe from becoming 'hot' in the event of a short of somekind. But the gas pipe should not BE the ground. In the latter case, current could flow in the gas pipe, and you do not want that.

Billy_Bob
04-02-2009, 08:09 AM
...How the heck did PG&E know I had a ground on the pipe (what were their sensors picking up?)...

Big companies can afford to buy big expensive test equipment!

Or it could be they just train their meter readers to be on the lookout for such connections and they saw yours.

As to finding this by testing... Gas companies have "cathodic protection systems" which are electrical gas line "electroplating" gizmos. Rather than an underground gas pipe deteriorating with age and then needing replacement, these systems sort of electroplate the pipe with the use of an underground electric current.

I'm sure they have all sorts of fancy test equipment to test these systems to be sure they are working. So perhaps they were not getting the reading they should and went looking for the source of the problem?

More on this...
http://en.wikipedia.org/wiki/Cathodic_protection