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Grounding a generator


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#1 Anya Shor

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Posted 22 June 2005 - 06:28 PM

I was talking to a couple of people, and they told me that you can ground a generator with a grip arm. how safe is that?
Sorry for the dumb question =)
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#2 Jeff Tanner

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Posted 23 June 2005 - 05:20 PM

I was talking to a couple of people, and they told me that you can ground a generator with a grip arm.  how safe is that?

<{POST_SNAPBACK}>



There is an ongoing argument about grounding generators...

According to what I understand of the NEC (National Electric Code) portable generators should not be grounded to earth at all. However, there are reputable Gaffers, set-electricians and certified electricians who all give different answers. Some say grounding is a must, some say it is extremely dangerous. Here's a bit of info that I received from the CML:

The complete discussion can be found in the NEC in section 250-6.
It is possible that the provisions of section 530 can also apply to
remote locations the way they apply to studios, and this depends on
the local inspector.

it is ILLEGAL to ground a generator being used for
motion picture use - in fact you must make sure that the safety chains
are not touching the ground. The only exception to this is if you are
powering equipment that is hanging on a metal structure or grid where
you are concurrently powering your equipment from "house power" in
which case the gennie should be grounded also.

A C stand arm pounded into the sand is not a ground. Oh, yes, and all the rules change above 600V.... but that's another section
of the NEC altogether.


[FONT=Arial]Check with some certified electricians in your area and ask them about NEC or local codes for grounding portable generators. This is not an issue to take lightly with so much electricity and so many people working with/around it.

Again, a c-stand arm is not a proper ground for anything.

Respectfully,

Jeff Tanner
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#3 timHealy

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Posted 23 June 2005 - 07:13 PM

To answer you question about a grip arm is no. There are specific codes for using grounding rods and I imagine the codes may change from country to country, and perhaps state to state under the NEC. There is absolutely no way that a grip arm is ever mentioned in any of these codes.

The question to ground or not to ground a generator is like asking which is better film or video.

for a great discussion about it can be found at

http://www.cinematog...g_Grounding.htm

In California where the film business is a big industry, they are much more strict about codes and violations and I believe a fireman/marshall can be found on most if not all sets. Someone with more knowledge about that can comment.

You will find that in CA it is illegal to ground a generator. But in NY you'll find many who will ground one. The CA law is written by humans. Electricity will not follow the laws humans but of physics.

You'll find many electricians who will say that if a mobile generator is insulated from the earth by rubber tires there is no potential if a live cable were to touch the earth. In a completely dry environment I would agree with that. But what if it were raining? What if cable was run through moist grass, dirt, mud, or pools of water? I find holes and cuts in cable all the time where the insulation on a cable was damaged from either from knife cuts or worn away down to the copper.

Read that thread. It is enlighting about both sides of the issue.

But the story I have that to me proves there is potential between an ungrounded insulated generator and the earth.

I was watching a 1200 amp generator when suddenly someone turned on something big on one phase. That something big was almost 400 amps of power. I called on the walkis to ask what it was and no one answered. So I start walking the line to find out where that load is coming from. I traced it to a distibution box with a few electricians huddled over it tryoing to solve another problem. I started tugging on the cable with the 350 amps on it asking what was this plugged in to when someone realized it was plugged in to a local ground that unknown to me, was attached to a small boathouse near a small fresh water lake. Yeah someone really screwed up to do that. When it was unplugged the load was disrupted and a hugh arc was seen by all. A closer inspection to the ground of the electric panel that it was attached to looked like a bolt of lightning hit it. The earth was taking as much power as the generator would produce. I can't iamgine in how many ways someone could have gotten hurt, but thank god no one did.

Even though there are arguments for grounding and not ground, I tend to think an earth ground from the generator is not a bad idea.

just my 2 cents

Tim
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