MadSci Network: Engineering
Query:

Re: Just a house meter question?

Date: Fri Dec 8 21:23:25 2006
Posted By: Donald Howard, Nuclear Engineering, Retired
Area of science: Engineering
ID: 1165508939.Eg
Message:

The subject of grounding electrical systems is complex.  I recently had my 
house rewired, and the electricians put in two ground rods: iron bars 10 
feet long and a half inch in diameter driven into the ground.  In some 
areas of the world, the ground wire may simply be tied to a water pipe
and use the water supply piping to the house as a ground.  

When you say you put a pipe in the ground, does it have as much surface 
area in contact with the soil at those two ground rods?  

It may, since you do measure 110 volts, but if that ground has a high 
resistance, not a "solid" ground, current flow through it will be 
restricted.  You should be able to measure 110 V from the hot side of an 
AC outlet to any part of your plumbing system - which is a lot of pipes 
buried in the ground.

Your local utility is using the earth as part of its distribution system.  
They recommend local grounding as a safeguard against lightning strikes, 
but without any local ground, your appliances, lights, etc. would work 
just as well.  

Your pipe just provides a current path in parallel with the utility's 
ground system.  Power still flows through the Watt-Hour meter to feed your 
house. 




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