"Vern Heiler" wrote in message
...
Thanks to all. It makes me feel better about writing them up having a
better knowledge of why.

Of equal importance to not bonding the neutral or grounded conductors on the
load side of the service is the importance of having a main bonding jumper
installed at the building service. Without the main bonding jumper a short
to ground will not trip the circuit breaker in many cases. I have found
main bonding jumpers missing in several inspections.
Let me give you a real life example that happened a Chena Hot Springs Resort
near Fairbanks, Alaska in about 1990 that almost got me killed.
A competent(?) master electrician had wired an 8 plex and I was performing
the final inspection. There was no rough in inspection since we don't have
State building permits here and I was the State Inspector. The building was
supplied from a generator at 240/120 volts located about 600 feet from the
building through an underground service lateral.
While preparing to write my inspection report I laid my metal tablet on the
Kitchen range of one unit. As I picked it up I accidentally placed my other
hand on the adjacent metal sink and received a jolt. I said what goes here?
I got my meter out of the car and checked and found 120 volts between the
range and the metal sink. Holy, mcMoley, I had just inspected the crawl
space and literal wrapped myself around metal pipes while crawling around.
I went to the service panel and checked there and again there was 120 volts
from ground to the neutral. The ranges had been grounded using the neutral
or grounded conductor and not the equipment grounding conductor as now
required. I had the master electrician come over to the open service panel
and asked him for a short piece of wire. I used the wire to temporarily
short the neutral bar to ground and whammo, a 20 ampere circuit breaker
popped. That 20 ampere circuit breaker fed a small water pump in the crawl
space. We went to it and found that the cover had pinched a hot wire to the
metal ground placing all the metal water pipes in the building at 120 volts
to whatever. We went back to the panel and sure enough the main bonding
jumper was missing. It was just a green screw that made the neutral bus
bond to the panel metal can and equipment grounding conductor.
There was a ground rod and it was bonded to the metal pipes and to the
equipment grounding bus in the service panel. Without the main bonding
jumper the fault current had to go through earth all the way to the
generator building to trip the circuit breaker and the ground resistance was
simply too high. The result was there was 120 volts potential between every
range and every metal sink in the entire building. The conclusion of this
is to never assume anything about the main bonding jumper. It is the first
thing I learned to look for when performing an inspection. Luckily, I lived
to tell this story.