2011 Mep 803 wiring for house

Please understand that I'm not telling you what to do. All I'm doing is trying to explain the framework of the rules. The choice to follow them is 100% in your court.

I do have a concern with one of your comments. If there is something that allows for a hot chassis with the bonding jumper removed in a generator there is a problem somewhere that needs to be found and repaired. Removing the bonding jumper should in no way affect the chassis ground of a set. This would suggest that the grounding conductor has a break or high resistance connection somewhere.

One more thing to comment on is these rules do change over time. When I was young and working as an electrician in the field a 3 wire system was OK. The rules in this area have changed in the last 10-15 years. If you don't work directly with this stuff it is very easy to fall behind the current acceptable methods.

If there is something specific that is confusing I am happy to share my thoughts on it. I won't necessarily know the local conventions but I do understand the NEC pretty well since it is part of my day job.

Potentially hot chassis if the generator or something else happens. In this instance, "hot" chassis referenced an ungrounded chassis that could become electrically charged due to a malfunction or even an external charging source.

Yea, I understand that. If removing the jumper makes that possible then there is a wiring fault somewhere. The chassis should remain grounded in a 4 wire system if the jumper is removed.

DieselAddict said:

Yea, I understand that. If removing the jumper makes that possible then there is a wiring fault somewhere. The chassis should remain grounded in a 4 wire system if the jumper is removed.

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.....and the unit remains connected to the house.

We have members that use a 4 wire system that may be interrupted by several methods, unplugging the connection, usings various methods to interrupt the hot, hot, or hot, hot, neutral, or even hot, hot, neutral and ground. Each one of our systems is different.

Placing a ground rod for a chassis ground is not a bad idea if the generator bonding to neutral is not used. What makes it so difficult is that neutral and ground are one in the same at the electric panel. Not so on the generator. On the MEP803a, in single phase mode, you in reality have, hot hot, ground (neutral), and ground. The entire purpose of bonding is to make neutral a ground which is a misnomer because there is no neutral in a live circuit. A neutral wire is one that has no connection to it, like a 2 foot piece of wire. That is neutral because there is no ground (not connected to earth ground) nor is there a hot lead to it. So it's a nothing wire, ie neutral.

We all know that at the panel that neutral, the white wire, and ground, the green wire, are bonded at the panel making both the white wire and ground wire one in the same. The white wire that connects to the panel from the generator is nothing more than a green ground wire because it is bonded to the ground wire at the panel which is attached to a grounding rod at the panel. Theoryretically, you can even leave the ground wire disconnected at the generator and you will still get power because you have a hot and ground for 120vac or a hot hot and a ground for 240vac. Is this not correct up to this point?

I know this to be true because I can go to any outlet in my house and disconnect the neutral white wire replace it with the ground wire, plug in my toaster and push down the handle and it will still work because it is a completed circuit.

So why have the white wire at all? Because not all appliances or other items are internally bonded. Two wire power tools, three wire power tools (don't remove the round prong on the plug, it is the bonding of the appliance or item now required by law when it was not in the past) they all function the same, a hot lead and an earth ground somewhere in the system.

Now, why have the fourth wire at all? Well unless it is for another hot lead, it seems pretty useless because all it is is a double grounding.

Here is where you get to the current carriers. Is my assessment of the above correct? If not, then this is where the disconnect takes place.

The only purpose for the green wire is chassis ground so you will not be used as a conduit between a hot source and Earth ground should the item malfunction and the hot wire accidently charges the chassis. If there is no conduit between the hot chassis and ground, you become it if you touch any part of toaster or whatever that has become charged and are in contact with earth ground somehow. This is why linemen can work on charged power lines from helicopters, there is no source to earth ground. It still scares the crap out of me to see them do this with 150000 volt live wires.



As an aside, I really hate Google keyboard and whomever designed the software should be ....... It takes me 4 times longer to type with this keyboard than it does on my computer.

I am going to move from my FPad to my computer.......

TECO power failure. No internet. Will have to finish later.

Dude.. That is WAY too much to be typing with a virtual keyboard. WOW.

What I have written below is not an attempt to convince you to change what you are doing. It is an explanation of why things have evolved to where they are today.

A couple of things from your post above. Neutrals.. They are not grounds. The are current carrying conductors. They can electrocute you as easily as the "HOT" can. The reason we can come in contact with them in "relative" safety is due to the N-G bond in the panel. That is a false sense of security. Any current carrying conductor can be a source of fault current. When we talk about fault current we are talking about energy that is not where it is supposed to be and energy that needs a place to go (safely). It will be happy to go through you. That is not the ideal place to send it. Lots of potential collateral damage with that scenario.

Now.. What I describe above is the reason for moving to a 4-wire system. There are inherit risks with using your fault conductor as a current carrying conductor. If anything causes a disruption in the current carrying ability of that single conductor you have lost your ability to give fault current a safe place to go. In the current code you are not allowed to use your fault conductor to carry anything but fault current. That is the rule. We may not agree with it but it is what it is.

So, how does this apply.. Since the ground and neutral are already connected together at the panel, when you connect the bonding jumper in the generator you have just created two parallel neutrals. The ground is no longer a fault current only conductor. It is now a current carrying conductor just like the neutral. We need to understand that electricity follows all paths. Any two wires connected together at the ends will share the power between them. If one wire becomes disconnected all of the power shifts to the remaining conductor. This is where leaving the jumper in place in the generator runs afoul of the code when you are connected to a 4 wire system. The sole purpose of a 4 wire system is to not allow anything BUT fault current on the ground wire.

On to another point. Inside a toaster the neutral should not be connected to the case (It may be connected in some very old appliances but not anything made in the last 40 years). The reality is there is nothing connected to the case of most toasters since they are considered double insulated. If you have an industrial toaster like what restaurants have they will have a 3 wire plug with a safety ground connected to the chassis. Neither of the load carrying conductors will be connected to the chassis.

I agree that if you are not paying attention and you disconnect the generator you loose your bonding point. Its easy to do.

Lets push all the code crap aside for a minute and ask the question - Is leaving the jumper in the generator a serious problem??

No. It is a code problem more than it is a real problem. Its only one you can be dinged on if you are on the wrong side of it. The chances of it causing any noticeable issues are very small.

Howdy,

KISS

Don't over think it.

In the field, ground rod in the ground, wired to generator, bonding strap in place.

At a house with a Service Panel, 4 wire connection with bonding strap removed.

Hello all, I hate to reopen this thread (BTW it was incredibly informative) but what do you do if you periodically load test you generator without connecting it to house panel? I believe there's no issue with the generator being permanently grounded with a rod (near the generator) even when connected to the house BUT does the bonding strap need to be reconnected when performing your periodic load test when the set is not connected to the house panel? Thx

You need a single ground to neutral bond in the system, so yes. However, I've made a work around so I don't have to repeatedly connect / disconnect my machine's ground to neutral bonding strap. I use an electric stove as a load bank and my ground to neutral bond is in the stove. When I connect to the house I'm using the house's ground to neutral. When I run a test I'm using the stove's ground to neutral. Not NEC approved, but I won't forget to disconnect the machine's bonding strap when the house's power goes off.

I've got a ground rod at my generator, too, but it's only around 40 feet from my breaker box.

Zed254 said:

You need a single ground to neutral bond in the system, so yes. However, I've made a work around so I don't have to repeatedly connect / disconnect my machine's ground to neutral bonding strap. I use an electric stove as a load bank and my ground to neutral bond is in the stove. When I connect to the house I'm using the house's ground to neutral. When I run a test I'm using the stove's ground to neutral. Not NEC approved, but I won't forget to disconnect the machine's bonding strap when the house's power goes off
I've got a ground rod at my generator, too, but it's only around 40 feet from my breaker box.

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Great idea and thx for the clarification.

enem178 said:

Hello all, I hate to reopen this thread (BTW it was incredibly informative) but what do you do if you periodically load test you generator without connecting it to house panel? I believe there's no issue with the generator being permanently grounded with a rod (near the generator) even when connected to the house BUT does the bonding strap need to be reconnected when performing your periodic load test when the set is not connected to the house panel? Thx

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I put a switch in place for the ground/neutral bond. If it's needed, flip the switch.

CallMeColt said:

I put a switch in place for the ground/neutral bond. If it's needed, flip the switch.
View attachment 777386

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Thats smart!

I leave my generator connected to the house for load testing. My transfer switch only switches the 2 hot legs, the ground and neutral are always connected....so no need to add another ground at the generator or mess with the bonding strap at the generator.