Using a ground as a neutral

[Jim Koepke]

When young my father often had me along as a helper when installing washers & Dryers. In those days most wall outlets were two prong instead of the three prong grounded outlet. Also in those days plumbing was all metal pipe, coper or iron were the most common. He would install a clamp on the cold water pipe and run a wire to the washing machine & dryer when needed.

jtk

[Dan Friedrichs]

The old practice of connecting neutral to a range or dryer chassis was, like all code provisions, a risk balance - the belief was that, being very infrequently unplugged, a range or dryer was unlikely to have a break in the neutral wire, so it could provide both functions with an acceptable level of safety. With experience and new information, the risk calculus now concludes that the cost and inconvenience of a separate ground wire is justified.

[Bill Dufour]

When young my father often had me along as a helper when installing washers & Dryers. In those days most wall outlets were two prong instead of the three prong grounded outlet. Also in those days plumbing was all metal pipe, coper or iron were the most common. He would install a clamp on the cold water pipe and run a wire to the washing machine & dryer when needed.

jtk

I think up to the 70's a washer included the ground clamp. I do not think my dad would have bought a new one and know he used a new one for the last washer he bought.
Bill D

[Maurice Mcmurry]

When the center tap of a transformer is zero volts, it is not a ground or vice versa. My Brit and European friends say "American 120 volt circuits are a cheat".

[Jim Koepke]

One problem of the neutral wire is it can have a voltage different than the ground.

Even though at some point the ground and neutral are bonded the distance from ground, an imbalanced load and the distance to the bond to ground can add up to an uncomfortable if not dangerous situation if one happens to be touching a stove while turning on the water.

jtk

[Frank Pratt]

It was only permitted to ground the frame of cooking appliances & clothes dryers to the neutral, up to when the 1996 NEC was adopted, now it is permitted in only in existing installations, it was NEVER permitted to use a grounding conductor as a grounded (neutral) conductor.

And that's an exception that never should have been allowed. I'd love to hear a good reason why it was, but I don't think one exists.

[Frank Pratt]

When the center tap of a transformer is zero volts, it is not a ground or vice versa. My Brit and European friends say "American 120 volt circuits are a cheat".

And they'd be dead wrong. The theory and implementation of the Edison 3-wire system is solid and safe.

[Bill Dufour]

And that's an exception that never should have been allowed. I'd love to hear a good reason why it was, but I don't think one exists.

Houses did not have a ground wire up until the 1960's. There is no good way to run a ground to an existing outlet clear from the panel. It was probably safer to use the neutral then to have no ground at all. I do not think you are allowed to tie a ground wire to the metal gas pipe on a stove?
Bill D

[Jim Koepke]

And that's an exception that never should have been allowed. I'd love to hear a good reason why it was, but I don't think one exists.

There may not be a good reason. The only thing that comes to mind is if the code at the time had neutrals tied to ground at the entry panel to homes.

jtk

[Brian Elfert]

And that's an exception that never should have been allowed. I'd love to hear a good reason why it was, but I don't think one exists.

I am thinking cost may have been an issue, but someone else mentioned that houses did not have grounds in the old days. I looked at an older house (1950s maybe?) for sale on a very large city lot and realized it did not have grounded receptacles. That was certainly one reason I decided the house was not for me.

[Andrew More]

The ground has always been a safety feature. A way to route a short into the earth, rather than shocking people or causing fire. This is the reason why you did not learn about the ground wire in high school science class, it's not part of the circuit, the hot and neutral are.

Further to have the ground wire work correctly the following factors need to come into play: there must be a short and the shorted wire must come into contact with some grounded part of the device. With today's modern plastic framed devices the likelihood of a failure of this nature becomes very unlikely. There just isn't any expose metal for people to touch.

That having been said, it's better to have it than not, since the cost with modern romex is relatively inexpensive. In the early days of Knob and Tube, running another wire was much more expensive, because they were much more careful about the way the wires were run: separated by about 6", each with an independent (hand drilled) hole, each hole with a ceramic insert, and all connections soldered together. With the move to all the wires together though a single hole, power tools to drill the holes, no ceramic insulators, and using wirenuts instead of solder it's become much much cheaper to run wires. The gauge of the wire is the same.

I honestly don't know which system is safer, I can't imagine the removal of ceramic insulators, soldering wires as an improvement. The distance between the wires in the old system makes animal problems less likely to occur. Generally speaking the issues with knob and tube are that it's old. Almost all the other issues, other than a lack of ground wire also happen with modern romex: people messing with it, overloading the circuit, shorts, etc.

[Brian Elfert]

Many of the problems with knob & tube come from people, especially unqualified homeowners, making changes or additions to the knob & tube wiring. It is not uncommon to see modern NM-B (Romex) cable spliced into a K&T circuit to extend the circuit. People try to run a modern household off of old K&T wiring and they often overload it. A house with K&T will often still have a fuse panel and people just install larger fuses when fuses blow due to circuit overload.

A new house wired to 2017 or 2020 NEC will very rarely have overloaded circuits as the code requires a lot more circuits these days. Lighting loads are decreasing due to LED lighting. Modern HVAC means it is very rare anyone will be plugging in a window A/C unit these days, nor a space heater. I ran a new dedicated 20 amp circuit to my bathroom in 2014. Last week the breaker tripped and pretty sure an electric toothbrush isn't going to overload a 20 amp circuit. I never did figure out why it tripped. My breaker panel was new in 2020 and all of the breakers are new since 2014.

[Andrew More]

Yes, like I said, overloading circuits and people doing dumb things is not limited to K&T.

Your breaker could be tripping because it's a GFCI or AFCI. Both are far more sensitive than older breakers, and they've started requiring them in modern panels.

[Bill Dufour]

K&T the wire is not always insulated. Not good to lean an aluminum ladder against it. or hang a metal coathanger over it. Obviously the power companies still use K&T it since no plastic insulation can withstand the high voltage in the sun and rain of a power pole.
Bill D

link is 230Kv insulator

[Lee Schierer]

K&T the wire is not always insulated. Not good to lean an aluminum ladder against it. or hang a metal coathanger over it. Obviously the power companies still use K&T it since no plastic insulation can withstand the high voltage in the sun and rain of a power pole.
Bill D

link is 230Kv insulator

K&T was originally insulated, but with time and critter help the insulation falls off. All the K&T I have encountered has been 14 gauge wire. It is not a good idea to leave it in place. My sister owned a house that supposedly had all the K&T replaced. What we found was the easily accessible wiring was replaced, but wiring in the walls was still K&T. They even pig tailed new outlets on romex that was tied into K&T behind the outlet box. Some was on 20 amp breakers. My Dad and I ran new runs to avoid the patch work and pulled out what was done wrong that we could reach.