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Old 07-29-2013, 06:53 AM   #1
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Grounding of generator

I have a 3000 watt yamaha generator with the inverter and boost technologies built in, it works fine other then the grounding aspect. I checked the ground (round)hole and one of the other slotted holes and found that only about half was being grounded. I mean with a multitester I checked both slots on a 110 recepticle on the generator, and then checked one slot and the round ground hole, ideally it should read the same but it doesnt. Even the the trailer shows this same reading from the generated power. I did ground generator to a ground stake and reads the same, whats going on? seems that I could have problems in a wet enviroment. Also this is a new generator.
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Old 07-29-2013, 08:23 AM   #2
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It appears that you are reading from the ground side to the "neutral" side of the outlet. When reading from the ground terminal to the " hot leg" you will read 120 volts. When reading from the ground terminal to the "neutral leg" you will read "0" volts. When reading from the " hot leg" to the "neutral leg" you will read 120 volts.
While I haven't owned the generator you have. I believe the neutral and ground legs are tied together internal to the generator.
Power Companies bond (tie the neutral to ground. But since your coach is considered a sub panel, the neutral and ground are not bonded within the coach.
What you are reading is correct if I understand your description.
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Old 07-29-2013, 09:52 AM   #3
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Twinkie is correct.

The ground and neutral should read no volts as they are the same lead on the generator.

On a modern polarized 120 AC outlet, the wider of the two slots is the "hot" side, if wired correctly.

Your trailer should show the same readings plugged into a shore line, too.

A simple device for testing AS wiring is available at any Lowes, HD or decent hardware store. Picture below. It is quicker and easier than a meter.



Also, a simple ground is not necessarily a safety in wet locations. The device that offers the most protection in that instance is a Ground Fault Interrupt.

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Old 07-29-2013, 10:21 AM   #4
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Quote:
Originally Posted by jdalrymple View Post
Twinkie is correct.

The ground and neutral should read no volts as they are the same lead on the generator.

On a modern polarized 120 AC outlet, the wider of the two slots is the "hot" side, if wired correctly.

Also, a simple ground is not necessarily a safety in wet locations. The device that offers the most protection in that instance is a Ground Fault Interrupt.

Regards,

JD
JD,

You have it backwards!

The longer vertical slot on a standard 120VAC 15 or 20 amp wall receptacle IS THE NEUTRAL. By international convention, the neutral wire in any AC wire is designated and marked, as it is in molded extension cords where the neutral wire is designated by the ribbing or stripes on the insulation.
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Old 07-29-2013, 10:49 AM   #5
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Well .............

Tried again, and still having no luck explaining this to myself. If on shore power meter reads as it should "0", however when hooked up to the generator, I get a reading of around 60 volts ! I tried both legs and in different combinations and still get around 60. I cant believe this new generator would be wired wrong. I am grounding the generator to a wall outlet box. Does this ground post on the generator only protect against static electrical shock ? The manual does not go into depth on this subject nor does it say of any other grounding problems.
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Old 07-29-2013, 11:12 AM   #6
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Lew,

You are correct. I misspoke. The wider slot is neutral. Sorry for the mistake.

Bait Guy,

The frame-mounted grounding lug of the generator should not be tied to the wiring of the trailer in any way.

Some folks tie this lug to the trailer chassis, but that idea opens a whole host of what-ifs.

A three conductor cord ("hot", neutral, and ground) from the generator outlet to the trailer shoreline input is the simplest, best way to use your generator.


Then test the outlets in the trailer with the device I suggested above to make sure you have no wiring issues inside the trailer.


JD
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Old 07-29-2013, 11:28 AM   #7
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From a yamaha expert ...............

Just got off the phone with the yamaha company, I of course got "bounced" around to a lot of different people, this is the best answer they gave me : Yamaha brand generators (they would not included any other brand) have a "floating" ground built into their generators, the external lug is not needed but they only have there to satisfy some picky customers, well anyways, the ground and neutral wires ARE NOT BONDED together as they do for shore power, so that is why I get my readings, I am only checking half of the circuit ! I hope this makes sense to the other people of this forum, it makes sense to me now.
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Old 07-29-2013, 03:13 PM   #8
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Generator ground system

The text below is from the Honda EU2000i Owners Manual. I suspect there is similar verbiage in the documentation for your Yamaha.

==========

Ground System

Honda portable generators have a system ground that connects generator frame components to the ground terminals in the AC output receptacles. The system ground is not connected to the AC neutral wire. If the generator is tested by a receptacle tester, it will not show the same ground circuit condition as for a home receptacle.
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Old 07-29-2013, 04:03 PM   #9
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Bait Guy;
Do you read 120 volts between the neutral and hot slots on the generator receptacle?
Since the ground is not tied to the neutral. It is known as a "floating neutral"
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Old 07-30-2013, 08:42 AM   #10
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Reading

Yes, I get 120 readout across the "upright" slots.
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Old 07-30-2013, 12:18 PM   #11
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Everything seems to be as it should be.
If you feel better about grounding the frame of the generator. Then drive a ground rod and wire it to the ground terminal of the generator.
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