Generator issue

I have a Coleman Black Max 5000w generator I use to charge my batteries and on occasion run a window AC in my cabin. The gen is wired to a small breaker box I removed from a camper via a large shore line type extension cord. After hooking up the gen last time down I thought I would check the wiring with a plug in polarity tester, it showed neutral and hot were reversed. This is inside the cabin as well as at the generator. I then checked voltage at the plugs and found from ground to neutral had apprx. 80 volts and ground to hot apprx. 40 volts???? I do not yet have a grounding rod installed but plan on doing so. Will the grounding help with the floating neutral? Or is something else going on? I've used this generator for about 5 years to power a camper and I'm going to guess this has been like this all along. Any thoughts or suggestion would be appreciated. Thanks Dan

WITHOUT going into the merits of how it SHOULD be done, if the neutral and ground are not connected/bonded at some point and you are measuring the difference in potential between them with a sensitive digital meter, the results you are seeing MAY be meaningless.

You should probably call an electrician. Hal

How did you measure those voltages, some of these cheap meters show voltages that are not really there, if those readings were really that high I suspect you would have some problems you could see and smell, did you measure this with the generator unloaded?

If it runs an AC you must have 100+ volts, they don't like low voltage. Did you chec the voltage with a significant load, that might be more accurate. We all waiting for John TTTTTTTTTTTTT's responce!

I don't think I'm smart enough to tell whats actually going on not being there and armed with my old fashioned less sensitive Simpson 260 ANALOG meter, so I will throw out a few thoughts:


1) Typically those small portable gensets would have the Neutral bonded to the metal case/frame and likewise the receptacles 3rd wire Equipment Grounding Conductor terminal is bonded to case/frame and Neutral. Thats the single point Ground. On a cheap unit I could imagine all that taking place in the receptacle outlet and that's a place a wire could be broke or missing ???

2) As far as Hot and Neutral being reversed, are you sure when you wired that breaker box the Neutral wired to the Neutral Buss and the Hot went to the circuit breaker?? With the setup you have I'm unsure if that "tester" can actually determine Hot and Neutral reversal??? But no warranty on that I just don't know the tester and how youre actually wired.

3) Typically an RV panel does NOT have Neutral bonded to Equipment Ground (like in a home entrance panel). The Neutral Buss is insulated and isolated off the case and Equipment Ground. That means if you ran a Hot and a Neutral and the 3rd wire Green/Bare equipment Ground to that RV panel, black Hot to breaker and white Neutral to the insulated stand alone Neutral Buss and the Green/Bare Equipment Grounding to the Ground Buss.

4) I dont think driving an earth ground rod will cure your problem. Heres the deal, its permissible to power plug and cord connected equipment from that genset provided the tool/appliance is plugged into on board mounted receptacles NO GROUND ROD REQUIRED.

HOWEVER if youre running the genset to a home breaker box and out of the box to feed loads (like AC etc) THEN THE GENSET NEEDS A GROUNDING ELECTRODE and it attaches to where the Neutral bonds to the case frame and the equipment Grounding Conductor.

PURE GUESSES AS TO WHATS GOING ON

Perhaps the Gennys Neutral is NOT connected to the case/frame or the 3rd wire equipment Grounding terminal. Id really look at that!!!!

Perhaps the RV panel is mis wired or Neutral and Ground are mixed up

If Neutral isn't connected to case frame and you have a sensitive high impedance digital meter its no telling what youre reading as voltage gets induced into parallel conductors.

Id insure the gennys wiring,,,,,,,,, its Neutral to case/frame and ground are bonded,,,,,,,,the RV panel is wired correct,,,,,,,,,,install a ground rod at the genset,,,,,,,,,,,,,try an analog meter and take some readings

Best I have to offer not being there

Im headed to Wisconsin later today in the RV and may or may not be back online so much the next week so yall take care and behave yourselves lol

John T

Yo Bob, FWIW (not a cent lol) I agree big time with that diagnosis. On a cheap genset the Neutral may not be bonded to the case/frame and Ground as it should be and with inductive and capacitive coupling in parallel conductors and a digital meter NO TELLING WHAT HES READING???

John T

Your keyboard must be like mine, sometimes the last keystroke stickssssssssssssss lol

John T

(quoted from post at 23:22:01 09/09/14) If it runs an AC you must have 100+ volts, they don't like low voltage. Did you chec the voltage with a significant load, that might be more accurate. We all waiting for John TTTTTTTTTTTTT's responce!

Click to expand...

First of all a voltage of 40 between line to ground and 80V neutral to ground is not a low voltage issue for connected loads.
Ground wires are not current carrying conductors.
The 120V loads are to be connected between line and neutral. The ground just holds metallic cabinets , cases, water lines etc to true earth potential.
I'll bet the generator is producing 120V between line and neutral.
For this cabin application. The generator should have an internal neutral to ground bond. The generator case should be connected to a ground rod. The cabin power panel needs the bond screw removed between the ground and neutral bar. The cabin ground bar needs to be connected to a ground rod.

In actuality, it is not a characteristic of Just cheap generators to have the neutral isolated from the ground conductor.

Case in point, the extremely popular and quite expensive Honda EU2000i generator which is arguably one of the most desirable generators for the camping world.

On that generator, the neutral is not connected to the ground lead.

It is built that way on purpose for several reasons.

On that generator as with most all of the generators of that design, the generator has two capacitors of small value connecting the hot lead and the neutral lead to the ground lead.

It is in a kind of voltage divider network.

On my Honda EU2000i, when I measure the voltages, with a digital voltmeter, I see 60 volts between the hot lead and the ground, and I see 60 volts between the neutral and the ground.

That is as it should be.

Then, when I measure the voltage between the hot and the neutral, I see the 120 volt output of the generator.

This is often a topic of conversations on many forums, with a basic question of why some loads will not operate correctly if one is attempting to run them on an EU2000i or similar generator.

Some new furnaces will not operate on a generator that has a floating neutral.

This happens when a homeowner isolates his furnace with just a pigtail power input lead to plug his furnace into a generator during power outages.

A very basic and simple solution is as follows. Most all of these generators have two outlets. Simply use one of them and at the other, insert a standard plug that has a wire connecting it's neutral and ground together, and nothing else.

That makes it so that the furnace sees the neutral and ground tied together and everything works.

Another potential problem is if a homeowner connects a generator to his house wiring through a transfer switch and the generator has the neutral connected internally to the generator's ground terminal.

If the transfer switch does not switch the neutral, the generator will have the neutral bonded to ground and the house wiring will have the neutral connected to ground as well, creating a ground loop situation that has been known to cause all kinds of strange problems.

The reason your generator did not produce identical voltage readings on the two tests is simple enough, the value of those two internal capacitors are not quite identical.

There is nothing wrong with your generator, more than likely it was wired that way when new.

But, remember, you may have to connect the neutral to the generator's ground for some appliances to work properly. Some new battery chargers are quite picky about that, it is not only furnaces. Some new washing machines are the same.

Thanks everyone for the replies, lots of good info. If I read correctly it sounds like I have a couple of things to do but, not a lot to worry about ...thanks again Dan

The generator must be loaded with at least a 100 watts or so of load to get an accurate measurement.

Interesting... you have me wondering how my Honda EU6500I is wired. I use mine as a whole-house generator. It is connected via the 220V plug to my breaker panel via one of those mechanical interlocks. To switch to generator I open the main breaker, hold up the interlock and close the breaker which goes to the generator receptacle out on the porch. It"s been this way for two years and everything works fine but I have no idea if I should be providing an earth ground or not.

I had an electrician install the entire setup.

I did read a post somewhere that some of the Honda industrial generators like the EU5000 (?) had issues when used as a whole-house generator due to something about the ground-neutral connection. Apparently there is a jumper you have to remove or replace - assuming you understand this stuff and know what you are doing.

To be honest with you, I am not familiar with a Honda EU6500i, but, I am familiar with the EU2000i, I have one of those.

I believe it to be that the EU6500i is wired with a floating neutral. I have read that it is.

This would be in compliance with the electrical code for a backup generator if it is to be connected to house wiring with a transfer switch.

You see, at the breaker box in your house, the neutral of your house wiring is bonded to ground.

You would not want the neutral bonded to ground at two different places, thus the floating neutral inside your generator.

Now, to answer your question about providing an earth ground, that is a different question entirely.

There is nothing wrong with connecting the frame (ground screw) on your generator's frame to an earth ground, although it is arguably not necessary.

That is not the same as connecting the generator's neutral to your generator's frame (ground).

Basically, you answered your own question, if your system has worked for two years, it is apparent you do not have a neutral/ground bonding problem.

It is those who do not use transfer switches who sometimes run into the floating neutral problem and when they do, it is when they isolate an appliance like a furnace and run it on an extension cord.

That is the way I do mine, my furnace runs on a pigtail lead that is normally plugged into an ordinary 120 volt outlet box near the furnace.

When I lose power, I unplug the furnace, and plug it into an extension cord that runs through the window out to my EU2000i.

I was prepared for it not to work because of the floating ground problem and had a plug wired up that I would have used, just in case I had to connect my generator's neutral to it's ground.

I found out by trying it, that although my furnace is of the newer type, it does not require neutral to be bonded to ground.

Thank you very much for the additional explanation. While my setup has been working it is beneficial to me to better understand the recommended configurations.

I initially considered the transfer switch route but didn't want to have to rewire all my circuits and be limited as to what I can power. By powering the entire panel I can pick and choose any of the circuits. Even though my generator is only 6500 watts I can pretty much run the entire house except for the central air and hot water heater. We have an oil burner furnace. I can run the water heater by itself if I first turn off a few other circuits.