Grounding Versus Bounding

I think the idea has been that if both hot leads and the neutral of a 240V feed to a home were "floating" with respect to ground, then accidentally grounding one of the hot leads may not be noticed at first, but would make the other one much more dangerous. By center-tapping the transformer 240V secondary as a neutral, and grounding it, the highest voltage to ground becomes 120V. If one of the hot leads does get accidentally grounded, it stands a good chance of kicking the breaker.

I don't know if this is a reason that was actually considered but it doesn't take much thought to agree it's a good idea. Lightning. If the grid floated and you had lightning strike the grid anywhere within miles the whole grid would "light up" so to speak. I would not want to be holding a hair dryer at that moment. Can you imagine what a million or more volts to ground might do in your kitchen or bath room?

Yes I beleive it is 1 of the primary reasons [Lightning].

look & you will see grounds for incoming telephone & cable {tv} service.

Common pratice is a nearly straight line from the incoming service to @ least a water pipe [ground].

i agree that bounding is good choice.

put it another way round. bounding improves the earthing of the equipments and facilities.

while the overall objective id earthing for protection from stray current or the like, bonding simply enhances that. bonding helps to ascertain that all linked points are protected.

idong archibong

Go to www.mikeholt.com

Gounding is supplying a ground path for fault current to ground, bonding is connecting all associated metalalic equipment to this path. The concept is just that.

You've got the two terms correct -

Bonding is to ensure overcurrent devices "trip" to open the circuit.

Grounding (earthing) is to ensure the grid/system/source has a zero-point that is connected well to the earth (and by NEC 250.32 in the US, this includes all metal building-connected systems as well as grounding electrodes) for stray current, with the largest source of this being Lightning.

High-impedence grounding systems, of course, operate under their own restrictive rules to ensure safety.

As the others have posted, bonding ensures that there is a good (low resistance) path for fault current to return to it's source (the utility transformer) and trip the overcurrent protective device nearest the fault. Earch grounding simply ensures that any (metal) parts that people can come in contanct with are at the same potential as the ground they are standing on. This greatly reduces the chances of accidental electrocution. Also, on a solidly grounded system, approximately 10% of the ground fault current flows through the earth - the balance of the current flows through the bonding connections and grounding conductor.