Open Ground question

ktmrfs wrote:

enblethen wrote:
Turning off breakers or on will not show a GFCI issue as breakers do not open ground or neutral leads. You must physically open that portion of the system. Problem could be any where in the 120 volt AC system.
Refer, water heater equipped with 120 volt AC element or converter would be places to start.

wrong, wrong wrong. opening a breaker will tell you if a given circuit has a ground fault, if the hot lead is open, which it is when the breaker is tripped, then there is no current flowing and no way to trip the GFI for a current imbalance in that circuit. close the breaker and if it trips the GFI then there is a ground fault in that circuit. So, it's a way to find which circuit has an imbalance.

If the GFI trips with an open breaker downstream, then the GFI is telling you there is a ground neutral bond in the ciruit.

so in the case of the OP, breakers are a good way to isolate the problem within a circuit.

GFCIs have grounded neutral detection in addition to the current imbalance detection and will trip on either fault. That is, they detect when the neutral and ground are connected and trip even if there is no load applied. (They do this by injecting a small common-mode signal on both the hot and neutral lines. If the neutral is grounded, some of this signal on it is diverted to ground and an imbalance exists to detect.)

The neutral and ground is common through the 120 volt electrical system. It is not isolated to a particular circuit. They are all tied together, neutrals on a neutral buss, grounds on a ground buss. From the rig they remain separate back to the electrical service panel where they are tied together by the main bonding jumper.

enblethen wrote:
The "leakage" between ground and neutral will be present at any time.

Not necessarily. Consider a simple heating element normally connected between hot and neutral, insulated inside a metal box that is bonded to ground. Now let’s say the element broke free from the neutral and fell against the case. Now there is no connection between ground and neutral and there will only be a current mismatch between hot and neutral if the breaker is on.

enblethen wrote:
The "leakage" between ground and neutral will be present at any time.

there will still be a leakage path, but there is only current flowing when the circuit is completed. open the hot side and the upstream GFI cannot see any any current flow.

ground and neutral will not have current flow between them since there is no way to complete a path UNLESS there is a connection to another hot ciruit. which is a no no and unlikely or if there is induced current from another circuit. but both of these are highly unlikely.

enblethen wrote:
Turning off breakers or on will not show a GFCI issue as breakers do not open ground or neutral leads. You must physically open that portion of the system. Problem could be any where in the 120 volt AC system.
Refer, water heater equipped with 120 volt AC element or converter would be places to start.

wrong, wrong wrong. opening a breaker will tell you if a given circuit has a ground fault, if the hot lead is open, which it is when the breaker is tripped, then there is no current flowing and no way to trip the GFI for a current imbalance in that circuit. close the breaker and if it trips the GFI then there is a ground fault in that circuit. So, it's a way to find which circuit has an imbalance.

If the GFI trips with an open breaker downstream, then the GFI is telling you there is a ground neutral bond in the ciruit.

so in the case of the OP, breakers are a good way to isolate the problem within a circuit.

enblethen wrote:
The "leakage" between ground and neutral will be present at any time.

Yes but the magnitude of the neutral to ground leakage will be much less then the hot to ground leakage because the neutral to ground voltage is "near" zero.

The "leakage" between ground and neutral will be present at any time.

wnjj wrote:

enblethen wrote:
Turning off breakers or on will not show a GFCI issue as breakers do not open ground or neutral leads. You must physically open that portion of the system. Problem could be any where in the 120 volt AC system.
Refer, water heater equipped with 120 volt AC element or converter would be places to start.

Generally true but there could be a device that only leaks current to ground when powered up and flipping breakers is simple to try as a first shot.

Your point is precisely why some have suggested unplugging the fridge to eliminate the heating element.

Which is why I said start by turning breakers off. If that doesn't come with anything, then time to dig deeper...

enblethen wrote:
Turning off breakers or on will not show a GFCI issue as breakers do not open ground or neutral leads. You must physically open that portion of the system. Problem could be any where in the 120 volt AC system.
Refer, water heater equipped with 120 volt AC element or converter would be places to start.

Generally true but there could be a device that only leaks current to ground when powered up and flipping breakers is simple to try as a first shot.

Your point is precisely why some have suggested unplugging the fridge to eliminate the heating element.

Turning off breakers or on will not show a GFCI issue as breakers do not open ground or neutral leads. You must physically open that portion of the system. Problem could be any where in the 120 volt AC system.
Refer, water heater equipped with 120 volt AC element or converter would be places to start.