I know what you mean on the pump houses 10/2 w/g was all all people used to use . I ve seen them drive a ground rod and bond it to a small panel in the pump house and say ok that 10/2 w/g is my power co and I grounded it just like they do . so whats wrong with connecting a 110 circuit ? . I had to admit two hots and a ground is two hots and a ground not matter how you get it .
But their statement of “two hots and a ground is two hots and a ground not matter how you get it†is incorrect.
What the power company supplies to a dwelling is two hots and a grounded conductor. The definition of ground by the NEC is simply, “earth†as shown here
Now couple this with the requirement found in 250.56 concerning the resistance of a rod and using Ohm’s Law we can see that two hots and a ground equals not much of anythihg.
250.56 Resistance of Rod, Pipe, and Plate Electrodes. A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8).
Using E=IXR and the 25 ohms mentioned above we can see that at 120 volts the earth would only carry 4.8 amps. In most cases connecting this 100 watt bulb to a 120 volt circuit using ground as a return path and the bulb will not burn.
When connecting this two conductor with ground to a 120 volt circuit what happens is the equipment grounding conductor is elevated to a potential of 120 volts. Anything connected to this equipment grounding conductor becomes energized to a potential of 120 volts.
The purpose of the equipment grounding conductor is outlined in 250.4 which states
(2) Grounding of Electrical Equipment. Normally non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
but what has happened is the voltage has been elevated and not limited.
Using this two conductor with ground to connect a 120 volt load to a 240 volt circuit using the EGC as the grounded neutral conductor in no way resembles what the power company delivers to a dwelling unit. It is nothing less than a death trap that will end up hurting or killing someone. The only question is when.