[HAM] Alignment of Start Motor. Warning about exposed AC mains

[John Doyle]

Kon,

A typical US residential electrical service has three wires coming to the 
meter. Two hot wires and a neutral. The voltage reading between the two hot 
wires is 220VAC. The voltage reading from either of the hot wires to the 
neutral is 110VAC. These three wires go to the electrical meter can. The 
neutral goes thru the can and directly to the service panel (breaker or fuse 
box). The two hots go to the service panel after going thru the electric 
meter. At the service panel there is a ground buss. The neutral is bonded to 
this buss. The neutral is called a grounded conductor since it does carry 
current but is is grounded.

This ground buss is supposed to be grounded in the following fashion. There 
should be a conductor of proper size going from the buss to both sides of 
the water meter. There should also be a conductor going from the ground buss 
to one or two grounding electrodes. These electrodes are usually a rod or 
pipe driven into the earth.

The US electrical code is ever-changing. The last couple of updates include 
more regulation regarding ground fault circuit interrupters (GFCI). These 
are usually required in areas where water will be present like kitchens and 
bathrooms. These devices measure the amount of current being supplied via 
the hot wire against the amount of current returning thru the neutral. If 
there is enough of a difference, the circuit opens. This is a good idea 
since the only other interrupting means is a 15 or 20 amp fuse or breaker. 
When properly grounded, 1/10 of an amp can kill a human. A normal household 
receptacle has 150 to 200 times what is needed to take you out.

JD