Open Ground question
Hi all, I have been having a problem with plugging into the shore power at our storage facility. They have all circuits run through GFCI outlets on the pole. When we plug in and we are not running any...
Forum Discussion
DrewE wrote: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.)
agreed. that's why I pointed out If the GFI trips with an open breaker downstream, then the GFI is telling you there is a ground neutral bond in the ciruit. circuit doesn't need to be hot downstream to trip on a ground/neutral bond. it will trip an upstream GFI either way. any downstream circuit must be hot for a GFI to trip on a current imbalance.
In most cases there is NOT a downstream breaker on GFI circuits, or most circuits for that matter, so it can be hard to distinquish between a ground/neutral bond vs a current imbalance.
So an RV protected by an upstream GFI poses both challenges (fault could be on one of many circuits) and advantages, (easy to determine if it is a ground/neutral bond or current imbalance).
