Problem Grounding a Generator

I recently acquired a small portable back up generator for nuisance
outages. Only paid $200 new. It is 2500 watts continuous, 3250 surge rated
and no 220 volt outlet, so I won't be hooking it up to a transfer switch.

Even though I'm going the extension cord method, I decided to properly
ground it, and use an inline GFI and surge protector. I'm willing to risk
using a back up computer with it, and I am hopeful that a surge protector
might clean up the "dirty" generator power.

Now the problem. I drove an 8 foot ground rod into typical soil, used a
correct copper clamp (nothing improvised), and connected the rod to the
generator ground lug with a single strand 12 gauge copper wire.

Trouble is, the generator outlets still tests as ungrounded.

I immediately suspected miswired outlets on the generator. So I tried
checking the resistance from the power receptacle outlet ground to both
the generator frame and the generator ground lug. Both tests resulted in
zero ohms of resistance. I'm thinking that would eliminate miswiring on
the generator as the cause.

I then removed both ends of the ground wire connection, checked and
reconnected them.

Same result, tests as open ground with a three prong plug in tester. I
also tested the tester, and it shows grounded outlets in my house as
properly grounded.

I checked the resistance from the generator end of the ground wire to the
ground rod itself. It was also zero ohms.

So it seems to be a case of it has to work, but it doesn't work. Any
suggestions are welcome.

--
Tony Sivori
Due to spam, I'm filtering all Google Groups posters.

On Sun, 15 Nov 2009 17:52:46 -0500, Tony Sivori <(E-Mail Removed)>
wrote:

>I recently acquired a small portable back up generator for nuisance
>outages. Only paid $200 new. It is 2500 watts continuous, 3250 surge rated
>and no 220 volt outlet, so I won't be hooking it up to a transfer switch.
>
>Even though I'm going the extension cord method, I decided to properly
>ground it, and use an inline GFI and surge protector. I'm willing to risk
>using a back up computer with it, and I am hopeful that a surge protector
>might clean up the "dirty" generator power.
>
>Now the problem. I drove an 8 foot ground rod into typical soil, used a
>correct copper clamp (nothing improvised), and connected the rod to the
>generator ground lug with a single strand 12 gauge copper wire.
>
>Trouble is, the generator outlets still tests as ungrounded.
>
>I immediately suspected miswired outlets on the generator. So I tried
>checking the resistance from the power receptacle outlet ground to both
>the generator frame and the generator ground lug. Both tests resulted in
>zero ohms of resistance. I'm thinking that would eliminate miswiring on
>the generator as the cause.
>
>I then removed both ends of the ground wire connection, checked and
>reconnected them.
>
>Same result, tests as open ground with a three prong plug in tester. I
>also tested the tester, and it shows grounded outlets in my house as
>properly grounded.
>
>I checked the resistance from the generator end of the ground wire to the
>ground rod itself. It was also zero ohms.
>
>So it seems to be a case of it has to work, but it doesn't work. Any
>suggestions are welcome.

You may have high resistance soil, and need more than one ground rod.
Code typically calls for three, wired together.

PeterD wrote:

> <(E-Mail Removed)> wrote:
>>So it seems to be a case of it has to work, but it doesn't work. Any
>>suggestions are welcome.
>
> You may have high resistance soil, and need more than one ground rod.
> Code typically calls for three, wired together.

I think you are probably right.

A quick Google shows that multiple ground rods are often necessary.
Although I found the NEC calls for multiple rods only when a single rod
installation exceeds it says 25 ohms. And it seems that every other
possible reason has been eliminated.

--
Tony Sivori
Due to spam, I'm filtering all Google Groups posters.

"Tony Sivori" <(E-Mail Removed)> wrote in message
news(E-Mail Removed)...
> PeterD wrote:
>
>> <(E-Mail Removed)> wrote:
>>>So it seems to be a case of it has to work, but it doesn't work. Any
>>>suggestions are welcome.
>>
>> You may have high resistance soil, and need more than one ground rod.
>> Code typically calls for three, wired together.
>
> I think you are probably right.
>
> A quick Google shows that multiple ground rods are often necessary.
> Although I found the NEC calls for multiple rods only when a single rod
> installation exceeds it says 25 ohms. And it seems that every other
> possible reason has been eliminated.
>
> --
> Tony Sivori
> Due to spam, I'm filtering all Google Groups posters.

I think I know what the problem is. In a house, at the electrical panel,
the neutral wire is connected to the ground. Your tester maybe assuming
this and that is why it is not showing a ground connection. Your generator
probably has a floating output (neutral not connected to the frame ground).
Which is why the tested shows no ground. This will not pose a problem when
using the generator, it is still grounded, it's just that the neutral is not
connected to ground.

Shaun

Andrew Erickson wrote:
>
> It sounds as though the generator's neutral leg is not tied to ground at
> the generator. The outlet tester isn't actually testing that the ground
> prong is anywhere near ground, merely that current can flow between the
> hot and the ground leg.

I wasn't aware of that. Thanks.

> (In a standard residential setup, the neutral leg is tied to ground at
> the main breaker box, and all neutral and ground wires go to the common
> neutral/ground bar.

That much I did know. I even knew that the only place the neutral can be
grounded is at the junction box.

> The outlet tester would still show the outlet is wired properly even if
> the ground leg were not actually connected to ground.)

A test with the outlet tester and an ungrounded outlet confirms that
you're right.

> By the way, the surge suppressor will do pretty much nothing to clean up
> the generator output power. It's also rather likely that the output is
> reasonably clean to begin with; certainly far better than a typical
> "modified sine wave" inverter output, which is a combination of a couple
> of square waves. A typical computer, with a switching power supply, is
> not picky at all about power quality, as the first stage in the power
> supply is a rectifier and reservoir capacitor, changing whatever the
> input is into (unregulated) high voltage DC power. They run just fine
> from the above mentioned modified sine wave inverters, potentially even
> a bit more efficiently than from sinusoidal inputs.

I've heard a few anecdotes of generator power damaging televisions and DVD
players. I thought a pair (one on each outlet) of cheap surge protectors
might help.

> Anyhow, you could tie the "neutral" leg of the generator output to
> ground at the generator, which would be safe provided the generator
> frame is actually grounded, and which would make the outlet tester
> happier.

Unless it would add safety, I'm not at all worried about bonding the
neutral to ground.

> Safer, IMHO, is just using the GFI and not worrying about it
> more. Indeed, code permits GFIs to be used on existing ungrounded
> circuits to allow three-pronged devices to be plugged in despite the
> lack of a safety ground conductor (albeit with certain cautionary
> labeling required).

I may do that. One of the reasons I was dead set on proper grounding is
that I knew that the surge protectors can't work without a ground. If the
surge protectors are useless and unneeded, I could leave the ground
connected as is, and just use the inline GFI.

--
Tony Sivori
Due to spam, I'm filtering all Google Groups posters.

Shaun wrote:
>
> I think I know what the problem is. In a house, at the electrical
> panel, the neutral wire is connected to the ground. Your tester maybe
> assuming this and that is why it is not showing a ground connection.
> Your generator probably has a floating output (neutral not connected to
> the frame ground). Which is why the tested shows no ground. This will
> not pose a problem when using the generator, it is still grounded, it's
> just that the neutral is not connected to ground.

You're right about the floating neutral.

I found a couple of OSHA pages discussing portable generator grounding and
neutral bonding.

http://www.osha.gov/OshDoc/data_Hurr..._generator.pdf

although it seems to contradict this one:

http://www.osha.gov/pls/oshaweb/owad...ONS&p_id=20448

--
Tony Sivori
Due to spam, I'm filtering all Google Groups posters.

On 11/15/2009 8:06 PM Tony Sivori spake thus:

> Andrew Erickson wrote:
>
>> (In a standard residential setup, the neutral leg is tied to ground at
>> the main breaker box, and all neutral and ground wires go to the common
>> neutral/ground bar.
>
> That much I did know. I even knew that the only place the neutral can be
> grounded is at the junction box.

Don't say "junction box", as that statement will make all electricians
wince. You meant to say "breaker panel" or "distribution panel", right?


--
Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the media as a condom?

- harvested from Usenet

David Nebenzahl wrote:

> On 11/15/2009 8:06 PM Tony Sivori spake thus:
>
>> Andrew Erickson wrote:
>>
>>> (In a standard residential setup, the neutral leg is tied to ground at
>>> the main breaker box, and all neutral and ground wires go to the common
>>> neutral/ground bar.
>>
>> That much I did know. I even knew that the only place the neutral can be
>> grounded is at the junction box.
>
> Don't say "junction box", as that statement will make all electricians
> wince. You meant to say "breaker panel" or "distribution panel", right?

A slip of the tongue, or fingers, if you prefer.

I've found some more pages on the pros and cons of bonding a
portable generator floating neutral to ground.

http://blog.rv.net/2009/10/generator...and-grounding/

http://blog.rv.net/2009/10/portable-...tor-grounding/

--
Tony Sivori
Due to spam, I'm filtering all Google Groups posters.

Tony Sivori wrote:
> I may do that. One of the reasons I was dead set on proper grounding
> is that I knew that the surge protectors can't work without a ground.
> If the surge protectors are useless and unneeded, I could leave the
> ground connected as is, and just use the inline GFI.

No relation to "wtom" ?

--
Best Regards:
Baron.

In article <(E-Mail Removed)>,
Meat Plow <(E-Mail Removed)> wrote:

> My generator is 2500/3250 surge like
> yours. And it is brushless. But there was nothing I could do to filter
> the output well enough where my two 1000va APC UPS units would come
> back off battery.

I've read elsewhere that the problem with generators and UPS units, is
that the generator doesn't hold an exact 60 Hz. You might find a
generator's frequency will range as much as 63 Hz to 59 Hz from no load
to full load. The UPS likely depends on a crystal controlled oscillator
to determine if 60 Hz power is present.

I wonder if inverter generators like the little Honda EU1000i, will work
with a UPS?

Fred