Circuit tester reading w house neutral disconnected?

[Peter Shepherd]

Would my circuit tester read neutral as being open if house neutral were
disconnected, but grounding electrode to water pipe was connected?

My understanding is that grounding electrode conductors have around 25 ohms
impedance, whereas house neutrals to transformers are about 2-5 ohms.

My electrical inspection teacher (for home inspection course) gave this as a
bonus question on our final, but wasn't sure himself what the tester would
read.

Thanks.



Peter Shepherd

 

[Bob Weiss]

Would my circuit tester read neutral as being open if house neutral were
disconnected, but grounding electrode to water pipe was connected?

If your electrical system is properly bonded to the incoming water
piping, and the piping has a continuous metallic path to your neighbor's
house (and to powerline neutral through their breaker panel), then the
water piping will act as a neutral return path.

A bit more voltage drop than usual, but it will work for a while.

 

[Ben Miller]

Would my circuit tester read neutral as being open if house neutral were
disconnected, but grounding electrode to water pipe was connected?

Assuming the typical three-light plug-in circuit detector, it will indicate
a normal circuit. It uses neon lamps that will light with several thousand
ohms in the circuit, so the earth resistance will not affect it.

My understanding is that grounding electrode conductors have around 25 ohms
impedance, whereas house neutrals to transformers are about 2-5 ohms.

That is a common misunderstanding. The resistance of the earth path back to
the transformer could be a lot more than 25 ohms. The 25 ohm figure is the
code requirement for a single made electrode, and is only the electrode to
earth resistance. The actual electrode to transformer resistance could in
fact be several hundred ohms.

Ben Miller