neutral or hot wire touch ground

[anbm]

What happen to 20A branch circuit protected by thermal magnetic breaker in below two cases? The breaker won't be tripped right?

1. Neutral wire touch equipment ground wire (or touch metal conduit)

2. Hot wire touch equipment ground wire (or touch metal conduit)

My understanding is this type of breaker will trip only when circuit is overloaded or having short circuit or breaker is defective?

 

[jusme123]

What happen to 20A branch circuit protected by thermal magnetic breaker in below cases? Tthe breaker won't be tripped right?

1. Neutral wire touch equipment ground wire (or touch metal conduit)

2. Hot wire touch equipment ground wire (or touch metal conduit)

This type of breaker will trip only when circuit is overloaded or having short circuit?

Do you expect us to do your homework? You think if you take a hot wire to ground (equipment ground wire or conduit) it will not trip the breaker, if so, what is the sense of the breaker?

 

[anbm]

Do you expect us to do your homework? You think if you take a hot wire to ground (equipment ground wire or conduit) it will not trip the breaker, if so, what is the sense of the breaker?

GFCI breaker will trip in above case but not regular breaker, will this make sense or I am wrong?

 

[augie47]

Give it some thought.....
Why do we ground the frame of a piece of equipment ? To keep it from being energized if the hot wire touches the frame. If hot to ground does not open the OCP device of any type we have a problem.

If you have 10 amps flowing through a 20 amp (SP) breaker and that same current flows through the neutral. If the equipment ground and neutral become connected, does that increase the flow of current through the breaker. No. The load has not changed.

 

[augie47]

GFCI breaker will trip in above case but not regular breaker, will this make sense or I am wrong?

You are correct.

 

[jusme123]

OCP Device= over current protection device (a circuit breaker)

 

[K8MHZ]

You are correct.

Are you sure?

You are saying a hot wire touching a ground wire won't trip a regular breaker?

I disagree.

EDIT:

I see where you said it would.

So...I just don't understand your answer.....if you are saying that a neutral to ground fault will trip a GFCI but not a regular breaker, that I understand.

 

[anbm]

Give it some thought.....
Why do we ground the frame of a piece of equipment ? To keep it from being energized if the hot wire touches the frame. If hot to ground does not open the OCP device of any type we have a problem.

If you have 10 amps flowing through a 20 amp (SP) breaker and that same current flows through the neutral. If the equipment ground and neutral become connected, does that increase the flow of current through the breaker. No. The load has not changed.

You mean if the neutral touch metal case, the breaker will open...

If the hot wire touch the metal case or equipment ground wire, the breaker won't open unless it has ground fault protection feature?

 

[K8MHZ]

What happen to 20A branch circuit protected by thermal magnetic breaker in below two cases? The breaker won't be tripped right?

1. Neutral wire touch equipment ground wire (or touch metal conduit)

2. Hot wire touch equipment ground wire (or touch metal conduit)

My understanding is this type of breaker will trip only when circuit is overloaded or having short circuit or breaker is defective?

1. In a non-GFCI breaker, there would not be a trip.

2. Yes, when hot touches ground, the breaker should trip.

 

[jusme123]

What happen to 20A branch circuit protected by thermal magnetic breaker in below two cases? The breaker won't be tripped right?

1. Neutral wire touch equipment ground wire (or touch metal conduit)

2. Hot wire touch equipment ground wire (or touch metal conduit)

My understanding is this type of breaker will trip only when circuit is overloaded or having short circuit or breaker is defective?

GFCI breaker will trip in above case but not regular breaker, will this make sense or I am wrong?

You are correct.

Augie, which case are you suggesting he is correct, # 1 scenario or #2 scenario?

 

[anbm]

1. In a non-GFCI breaker, there would not be a trip.

2. Yes, when hot touches ground, the breaker should trip.

I see your point, what is the difference between hot touch ground and neutral touch ground???

 

[K8MHZ]

I see your point, what is the difference between hot touch ground and neutral touch ground???

The neutral is already bonded to the ground in the panel. No additional current will flow if they come in contact with one and other at any other point in the circuit. (to speak of).

When the hot touches the ground, the current is large and flows from hot through the grounding wire and back to neutral, causing a large amount of current to flow through the breaker and trips it.

As far as the breaker is concerned, a hot touching a neutral and a hot touching a ground are the same thing (short circuit) and will trip when either happens. That is the whole purpose of the design, to make sure the breaker opens when a hot touches a ground, like the grounded metal chassis of a radio or a wash machine.

 

[charlie b]

. . . what is the difference between hot touch ground and neutral touch ground???

Others have answered this aready, but with a hot-to-ground (or hot-to-neutral) short circuit, a large current will flow, and the breaker will trip, regardless of whether the breaker is GFCI or non-GFCI, and regardless of whether the load is turned on or not. With a connection between neutral and ground, a non-GFCI breaker will not trip. That is because this does not create a large amount of fault trip. However, with a connection between neutral and ground, a GFCI breaker might trip, and it might not, depending on whether the load is turned on or not. Before you connect the neutral to the ground, if the load is running, then some current is flowing in the hot wire, and all of that current is returning via the neutral. The two wires have the same current, and that is what the GFCI device is measuring. If the load is running, and you then connect the neutral to ground, the same amount of current will flow in the hot wire, but the current returning to the source will be shared between the neutral wire and the ground wire. Therefore, as the GFCI device compares the currents in the hot wire and the neutral wire, it will see a difference, and it will trip. Finally, if the load is turned off, and you connect the neutral to the ground, nothing will happen, not even with a GFCI breaker. That is because no current is flowing in the hot wire or the neutral wire, and the GFCI device will not detect a difference in those two currents.

 

[anbm]

Others have answered this aready, but with a hot-to-ground (or hot-to-neutral) short circuit, a large current will flow, and the breaker will trip, regardless of whether the breaker is GFCI or non-GFCI, and regardless of whether the load is turned on or not. With a connection between neutral and ground, a non-GFCI breaker will not trip. That is because this does not create a large amount of fault trip. However, with a connection between neutral and ground, a GFCI breaker might trip, and it might not, depending on whether the load is turned on or not. Before you connect the neutral to the ground, if the load is running, then some current is flowing in the hot wire, and all of that current is returning via the neutral. The two wires have the same current, and that is what the GFCI device is measuring. If the load is running, and you then connect the neutral to ground, the same amount of current will flow in the hot wire, but the current returning to the source will be shared between the neutral wire and the ground wire. Therefore, as the GFCI device compares the currents in the hot wire and the neutral wire, it will see a difference, and it will trip. Finally, if the load is turned off, and you connect the neutral to the ground, nothing will happen, not even with a GFCI breaker. That is because no current is flowing in the hot wire or the neutral wire, and the GFCI device will not detect a difference in those two currents.

Will this act same (neutral-ground connection) to electronic breaker with ground fault protection feature?

 

[iMuse97]

Will this act same (neutral-ground connection) to electronic breaker with ground fault protection feature?

Aif you are asking about the last mentioned scenario in Charlie B.'s post, yes. nothing will change. You need to do some real-life testing of circuits.

1. Lift the 120V ungrounded conductor of a 15A, GFCI protected circuit and touch it to the grounded conductor (neutral). It will trip.

2. Then reset the breaker and touch it to the grounding conductor (equipment ground). It will trip.

3. Then re-land the ungrounded conductor. Jumper a wire from the grounded conductor to the grounding conductor. Nothing will happen.

Do this on your own time in your own house. Nothing in my recommendations in OSHA approved or in any other way is an encouragement to do anything that would jeopardize your safety or that of anyone around you. Proceed at your own risk.

 

[readydave8]

theory or real life?

theory or real life?

As we all know, hot can touch ground or grounded metal, spark, melt metal, and sometimes not trip the breaker. I may be wrong but it seems to happen more often the longer the run back to the breaker, is it possible that resistance of wire affects breaker tripping?

And many of us have cut a live romex, ruined our Kleins, cussed and then, assuming that the breaker must have tripped, done it again.

So any lab experiments inspired by this thread should be carried out with caution, or not at all.

 

[anbm]

Aif you are asking about the last mentioned scenario in Charlie B.'s post, yes. nothing will change. You need to do some real-life testing of circuits.

1. Lift the 120V ungrounded conductor of a 15A, GFCI protected circuit and touch it to the grounded conductor (neutral). It will trip.

2. Then reset the breaker and touch it to the grounding conductor (equipment ground). It will trip.

3. Then re-land the ungrounded conductor. Jumper a wire from the grounded conductor to the grounding conductor. Nothing will happen.

Do this on your own time in your own house. Nothing in my recommendations in OSHA approved or in any other way is an encouragement to do anything that would jeopardize your safety or that of anyone around you. Proceed at your own risk.

So when will the ground fault feature in an electronic breaker be tripped???

 

[iMuse97]

So when will the ground fault feature in an electronic breaker be tripped???

When there is a fault from the ungrounded conductor or within the equipment itself to the grounding conductor (equipment ground or case which is bonded to equipment ground). This is the action which defines a ground fault, and it is what a GFCI (ground fault circuit interrupter) is designed to detect.

This detection and circuit interruption eliminates the possibility that exposed metal on the equipment will become energized and create a dangerous and life-threatening condition.

 

[kwired]

Should we really add confusion and say we are now dealing with an ungrounded system? High impedance ground system?

 

[anbm]

Is this summary correct?

1) Hot wire touches Hot wires: Short circuit --> Breaker will trip

2) Hot wire touches Neutral wires: Short circuit --> Breaker will trip

3) Hot wire touches Equipment ground wires (or metal enclosure): Ground Fault --> Breaker will trip

4) Neutral wire touches Equipment ground wires (or metal enclosure): Ground Fault --> Only breaker with ground fault protection feature will trip (GFCI breaker or Electronic breaker with ground fault relay/protection)

Item #4: Per NEC, neutral wire and Equipment ground wires should not bonded together except at service disconnect or separate derived system, etc.