GFCI Question

[Bruceper]

When not on shore power, it would be possible to mitigate the chassis from being energized. That would be through the use of an earth ground.

You would need a ground strap connected to a conductive rod that would be spiked or hammered into the ground. The depth of the ground rod would be at least three feet into moist soil but most electrical code will specify deeper.

If you have a generator, read the manual and you will see that it says something along the lines of "Be sure to attach to an earth ground before using".

Here's what OSHA has to say about grounding generators

Grounding Requirements for Portable and Vehicle-mounted Generators
Under the following conditions, OSHA directs (29 CFR 1926.404(f)(3)(i)) that the frame of a portable generator need not be grounded (connected to earth) and that the frame may serve as the ground (in place of the earth):

• The generator supplies only equipment mounted on the generator and/or cord and
plug-connected equipment through receptacles mounted on the generator, § 1926.404(f)(3)(i)(A), and
• The noncurrent-carrying metal parts of equipment (such as the fuel tank, the internal
combustion engine, and the generator’s housing) are bonded to the generator frame, and the equipment grounding conductor terminals (of the power receptacles that are a part of [mounted on] the generator) are bonded to the generator frame, § 1926.404(f)(3)(i)(B).

Thus, rather than connect to a grounding electrode system, such as a driven ground
rod, the generator’s frame replaces the grounding electrode.

If these conditions do not exist, then a grounding electrode, such as a ground rod, is required.

[JohnnyFry]

In following this discussion, a couple of points have been missed.

First: The operation of a GFCI does not require a ground of any kind. A ground point is not used in the operation of the circuit. Basically, a comparator circuit senses the current flowing in both sides of the outlet, that is, the current going out one prong and the current returning through the other prong. If there is a difference of 16mA the circuit activates to shut off both sides of the outlet. I researched this in working with ungrounded neutral power systems on ships where neutral is not referenced to ground. I know, the G in GFCI stands for ground because the usual case implies current going to ground through someones body...they would probably have better named the device a DCCI (Differential Current Circuit Interrupter). When there is a difference in the current, the current is flowing somewhere else, probably through your body or some other path rather than back into the outlet where it was sourced.

Second: The necessity of a grounding rod for a generator is questionable for this reason: The generator frame itself is attached to the frame of the vehicle making its own self contained grounding system. The only connection to "Earth" is through the tires which, being rubber, are insulated. Therefore there is no way in which the skin of the vehicle could become "hot" with reference to the earth. That said, there are 2 exceptions to this: If the generator is external (i.e.: sitting on the ground outside the vehicle) it is possible for the generator frame to leak to ground. In this case it is necessary that a firm ground be run between the generator frame and the RV chassis, (although a 3 wire properly wired supply cable would normally accomplish this).

The second case is a park outlet with a lifted ground connection. In this case the system ground is provided by the power company and if it is not carried through to the RV chassis the vehicle could, indeed, become "hot" referenced to earth ground. In this case a grounding rod could be used to accomplish this (not ideal because ground resistance might be high due to soil conditions and you could get shocked.) it would probably be better to move to another site with proper wiring.

[booster]

Originally Posted by JohnnyFry

In following this discussion, a couple of points have been missed.

First: The operation of a GFCI does not require a ground of any kind. A ground point is not used in the operation of the circuit. Basically, a comparator circuit senses the current flowing in both sides of the outlet, that is, the current going out one prong and the current returning through the other prong. If there is a difference of 16mA the circuit activates to shut off both sides of the outlet. I researched this in working with ungrounded neutral power systems on ships where neutral is not referenced to ground. I know, the G in GFCI stands for ground because the usual case implies current going to ground through someones body...they would probably have better named the device a DCCI (Differential Current Circuit Interrupter)



Second: The necessity of a grounding rod for a generator is questionable for this reason: The generator frame itself is attached to the frame of the vehicle making its own self contained grounding system. The only connection to "Earth" is through the tires which, being rubber, are insulated. Therefore there is no way in which the skin of the vehicle could become "hot" with reference to the earth. That said, there are 2 exceptions to this: If the generator is external (i.e.: sitting on the ground outside the vehicle) it is possible for the generator frame to leak to ground. In this case it is necessary that a firm ground be run between the generator frame and the RV chassis, (although a 3 wire properly wired supply cable would normally accomplish this).

The second case is a park outlet with a lifted ground connection. In this case the system ground is provided by the power company and if it is not carried through to the RV chassis the vehicle could, indeed, become "hot" referenced to earth ground. In this case a grounding rod could be used to accomplish this (not ideal because ground resistance might be high due to soil conditions and you could get shocked.) it would probably be better to move to another site with proper wiring.

The second item mentioned is what I mentioned earlier. The hot chassis comes from open ground on shore power, the hazard from inverter comes from having a"hot earth ground" due to having a hot short to earth ground from an appliance that is plugged into the van, or generator. In the case of the "hot earth ground", a ground rod would be of safety benefit, because it would complete the circuit from earth and the neutral and ground on the van, and by doing so would eliminate the voltage between the ground and the van that could travel through you if you are standing in water and touch the van, while the hot short to ground is happening.

[Saldar]

I'm not able to follow the electrical upshot here, but it sounds terribly important. Are these the kind of dangers a "Progressive Industries Hard-Wired Portable Electrical Management System" would help protect against? We just ordered one for our new Travato.

[cruising7388]

Originally Posted by Saldar

I'm not able to follow the electrical upshot here, but it sounds terribly important. Are these the kind of dangers a "Progressive Industries Hard-Wired Portable Electrical Management System" would help protect against? We just ordered one for our new Travato.

If what you ordered is one of the EMS serires protectors, IMO you are getting the best protection available. Get the inexpensive remote to make monitoring convenient.

EMS-HW30C 30 Amp Hardwired EMS with Remote Display

[booster]

It appears that it would protect against the open neutral on shore power, but likely would not catch the generator, inverter, "hot earth ground" situation. Most of the time, the generator and almost all the time the inverter, are not even wired through the power protector, anyway.

[cruising7388]

Originally Posted by booster

It appears that it would protect against the open neutral on shore power, but likely would not catch the generator, inverter, "hot earth ground" situation. Most of the time, the generator and almost all the time the inverter, are not even wired through the power protector, anyway.

It's primarily designed to analyze shore power but will also monitor generator output depending on where in the AC path you insert the protector. I wired mine downstream of the transfer switch so it was also able to monitor the generator.

[JohnnyFry]

You have the best protective box on the market. It will protect you when hooked up at a campground from: overvoltage, undervoltage, hot/neutral reversals, ground/neutral reversals, (all of which can and do occur in campgrounds), and high voltage spikes (think lightning, especially in Florida). It will sacrifice itself in a lightning situation, however, and PI will fix it for free in this case.

It will probably not protect you with the generator, but that is not usually a problem as the generator is hard wired into the electrical system and does not present the misconnection issues present with shore power connections. Although not typically done, it could be wired in such a way to do this. The GFIC should give you positive protection against electrocution.

[booster]

Originally Posted by JohnnyFry

You have the best protective box on the market. It will protect you when hooked up at a campground from: overvoltage, undervoltage, hot/neutral reversals, ground/neutral reversals, (all of which can and do occur in campgrounds), and high voltage spikes (think lightning, especially in Florida). It will sacrifice itself in a lightning situation, however, and PI will fix it for free in this case.

It will probably not protect you with the generator, but that is not usually a problem as the generator is hard wired into the electrical system and does not present the misconnection issues present with shore power connections. Although not typically done, it could be wired in such a way to do this. The GFIC should give you positive protection against electrocution.

I don't think the power protector includes a GFCI, it would have to be a 30 amp one, and many vans don't have GFCI on all the outlets. Getting the GFCI protection is why I rewired our van to run all of the outlets off of the inverter, same as if on shore power, through the internal 30 amp transfer switch in our inverter/charger. That allowed me to put GFCI breakers in the main panel, so all outlets would always be protected no matte where the 110v AC was coming from. We do have a hardwired PI power protector in also on the shore line, also.

[cruising7388]

Originally Posted by JohnnyFry

It will probably not protect you with the generator, but that is not usually a problem as the generator is hard wired into the electrical system and does not present the misconnection issues present with shore power connections. Although not typically done, it could be wired in such a way to do this. The GFIC should give you positive protection against electrocution.

You're right, once the generator is correctly hardwired, you're delivered from pedestal issues created by some campsite maintenance and repair ignoramus, but nevertheless it provides valuable protection from a generator malfunction like a regulator gone bad causing over/under voltage conditions and, particularly, out of tolerance frequency deviations.

[avanti]

Before you spend a lot of money on one of those fancy power monitors, check what protections you already have. If you are running your power through an inverter/charger with an internal transfer switch, there is a good chance that most of the expensive features of an external monitor are redundant. That would certainly be the case with my Outback inverter. I basically already had everything except surge suppression. If this is the case, you can get better protection for much less money by installing a residential whole-house surge suppressor from Home Depot. I use this one:

surge.jpg

[booster]

Originally Posted by avanti

Before you spend a lot of money on one of those fancy power monitors, check what protections you already have. If you are running your power through an inverter/charger with an internal transfer switch, there is a good chance that most of the expensive features of an external monitor are redundant. That would certainly be the case with my Outback inverter. I basically already had everything except surge suppression. If this is the case, you can get better protection for much less money by installing a residential whole-house surge suppressor from Home Depot. I use this one:

Attachment 4114

We discovered the same thing when we put in the Magnum, all there except surge, but we already had the PI, so just left it in place. Of course we still have the plug in monitor/alarm we had before the PI, too, which is kind of useful to see how good the power is out of the inverter.

[Saldar]

Our new 59k travato doesn't have an inverter. I have read about installing the PI before (protects switch) or after the transfer switch (to include protection from generator). I hope/expect our generator is connected safely. I bet the PI will go where it fits in easiest. Thank you for the reassuring information.