Grounding a generator

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I believe that the neutral is bonded to the frame.
I also expect to have a transfer switch that will only switch hots.
i plan on having separate neutral and ground wires going from home to the genset.

That's exactly why I want to explore opinions and come up with a solid plan. I do not want to have the generator grounded separately without need.
i

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Ron and I agree. I was just trying to avoid some of the NEC speak that confuses people. The point is you only want one bonding point between the neutral and ground and if the transfer equipment doesn't switch neutral that will be the jumper in your service panel. (Separately derived source is NEC speak for a system where the neutral is switched too so it will have separate bonding jumpers that go with the source). All the frame grounding will be bonded, no matter what the transfer scheme. Adding another electrode only insures that the ground on the case is more closely referenced to the dirt under your feet when you are standing there. Depending on where you live "ground shift" is more or less of a problem. Here is the sandbox (Florida) I have seen 35 volt transients across 30-40 feet between buildings.
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For my operations, I have all the gensets wired with the Neutral, Ground, and both Hot Legs comming out as sperate wires. They then connect to the Main Transfer Switch where both Hot Legs and Neutral, are switched. The Neutral and Ground are Bonded at the MAIN 240Vac Panel, which is where the Grounding Rod is also connected. At the 240/120Vac Transformer, the Neutral on the 240Vac winding goes back to the Neutral at the Main Panel, and one side of the 120Vac winding is brought to the Neutral Buss in the 120Vac SubPanel, which is also Bonded to the Ground Rod, to establish Neutral and ground for the secondary side of the Transformer. One Breaker in the 120Vac SubPanel feeds the Input to my 4024 Trace inverter, which then feeds the 120Vac Inverted SubPanel, where the Neutral and Ground are not bonded. This is because the Ground Connection on the Inverter is common to both Input and Output, therefor the bonding in the 120Vac SubPanel sets the Ground on both sides of the Inverter. The 120Vac Inverted SubPanel then feeds the Cabin Subpanel, as well as the ToolShed and GenShed Circuits.
Bruce in alaska
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Thanks, that's interesting.
i
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I've seen this "IgnoramusXXXXX" stuff for years. What is the story?
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You are connecting this to your home wiring with a transfer switch that switches only the hot connection. Is that correct?
I used to have a link to a long article that went into extreme detail and all that, but have misplaced it. Oh well. Anyhow...
If your generator ground is bonded to generator neutral, you MUST use a transfer switch that switches both hot and neutral, and you MUST ground the generator.
If your generator is not bonded (and no normally available generators are bonded afaik, but your monster...) then you can switch only the hot and MUST NOT ground the generator.
The article went on for pages about ground loops or somesuch thing (the neutral being grounded in two different places). So, my suggestion is that you find out if you can unbond your generator, since you are unlikely to find a transfer switch to switch both hot and neutral. There is no need to ground the generator separately, since it's ground is not connected to anything except the house ground.
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That would be my plan, yes. I have not yet bought the transfer switch, but all ones available for "homeowners" seem to be such.

Which I think is the case, I will check tonight with an ohmmeter.

Aha. Thanks. It makes sense, logically.

Okay. I will check for sure tonight or soon, and will report my findings.

I will check and post updates. I am not sure just what possible dangers to the generator could be created by unbonding.
i
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wrote:[snip]

prohibited by the NEC, multiple hot-neutral bonds are quite common. He has seen the question raised in professional meetings, and the answers were always sketchy.
It seems that some electronic equipment is affected by noise impressed onto ground, but the problem is overrated.
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Hot-neutral bonds?????????????????
i
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wrote:

resistance one. Second hand information from a "professional electrician"... geez, when I see some of the work done in the past on my house by professional; my 23a water heater was run with #12 on a 30a breaker, a multiwire circuit was all on the same leg, etc.
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toller wrote:

A bond implies no -middle man- sort of load between two conductors.
The gentleman meant to say ground to neutral connections.
The guy doing your wiring should have been fired. A number twelve wire suitable for house wiring is usually rated for 20 amps. Heating loads have to use no more than 80 percent of the wire 'ampacity.
So, his number 12 was good for only 16 amps in this situation.
a 30 amp (#10) wire would have barely met the legal requirements (.8 X 30 = 24)
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wrote:

I wonder if the water heater woudl be considered a 'continous load' like a houses heating, but it does make sense even without the derating, #12 shouldn't be used on a 30am breaker.
I'm guessing it was a typo.
later,
tom @ www.FindMeShelter.com
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I replaced the #10 with #12, and put each 20a circuit on its own 20a breaker.
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toller wrote:

12 with 10..<g>
mike
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wrote:

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Ignoramus24153 wrote:

I have done that many times, it's why I'm always buying new screwdrivers. Quite a show when it happens :-( Dave
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wrote:

I am sure that he is referring to multiple bonding points to the neutral. Your supposed to do it once at the service. The neutral is a "grounded current carrying conductor" Having it grounded/bonded in more than one place just increases the probability of something going wrong. Does it happen you bet, is it correct. NO
If you ground to your service, best in my opinion. Use the same size ground wire as your service. You are creating an "supplemental ground" for the service. Any ground conductor smaller than the ground for the service could create a weak link in the grounding. Bonding to the metallic piping systems is required. This may not be a problem if you are able to come off of the ground bar in the service. Assuming that the metallic piping systems are bonded currently.
Personally I like and use only switched neutral transfer panels. Solid neutral switches are available and a little cheaper. I have had to many problems with sensitive electronics over the years. If my customer insists then they find someone else to do the job. Almost all that have in the past have come "crawling back" for me to fix it AFTER the damage was done. They are very careful not to discuss or complain about price. Having two sources of power is not rocket science. It is problematic when incorrectly installed. If you land on a solid neutral block, you will have a the possibility of current traveling to your generator while it is off. Switching the neutral with the phases assures that the generator will be completely isolated when not being used.
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I completely agree and will do it by the code.
i
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I do not know exactly what the code says, but I do know what makes sense from a safety perspective. The neutrals of all circuits should be connected to ground at ONLY one place - in your main service panel. There must be no grounding of neutrals in sub panels. Ranges etc. connected to sub panel circuts should use a 4 pin connector (hot, hot, neutral, ground).
The ground wire from your main panel may be connected to multiple grounds and it's best if these are close together. Two grounding rods are frequently used for a lower resistance ground path and better reliability.
Do not ever use a pipe as a ground. The water supply line may be PVC or may be changed to PVC at some time in the future and you would have no ground.
Since a good ground is so important, use the gauge wire required by code or larger, protect it where required and never allow a splice in it. Use only the best quality U/L approved grounding clamps and be sure all contacting surfaces are clean and tight.
All of this applies to your generator too. For best safety, if your generator is outside, it should be physically close to your system ground.
If the code requires anything less, it should be changed.
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snipped-for-privacy@aol.com wrote:

The US NEC requires that any underground water piping that is ten feet or more in length shall be used as a grounding electrode. That is not optional. No matter how authoritative a posting recomending against this sounds it is bad advice for anyone who's work is governed by the US NEC.
If the underground water piping were too short or non conductive the code would require that any interior metal water piping that is likely to become energized be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. That connection is required regardless of whether there is any underground metal water piping present. Most Authorities Having Jurisdiction (AHJs) consider any metallic water piping that supplies water to any electric appliance as likely to become energized and although most AHJs will except the Equipment Grounding Conductor (EGC) of the electrical equipment attached to the piping as the bonding means for interior gas piping they will not except an EGC as the bonding means for water piping. For water piping the bonding conductor must comply with 250.104 of the US NEC which requires it to be sized exactly the same as an Grounding Electrode Conductor (GEC).
[250.50 Grounding Electrode System. If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.
250.52 Grounding Electrodes. (A) Electrodes Permitted for Grounding. (1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.
250.104 Bonding of Piping Systems and Exposed Structural Steel. (A) Metal Water Piping. The metal water piping system shall be bonded as required in (1), (2), (3), or (4) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible. (1) General. Metal water piping system(s) installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 except as permitted in 250.104(A)(2) and (A)(3).] Copyright 2002 the National Fire Protection Association.
Failure to follow the electrical code that is enforced as law in your area can void your fire and liabilty insurance if that failure results in an otherwise insured loss. It is considered a legal obsurdity to attempt to insure against the cosequences of the insureds own unlawful act. Insurance contracts are "contracts of utmost good faith." That means that all parties to the contract must scrupulously obey the law in all matters that could affect any other party to that contract. To fail to do so allows the other party to walk away from their obligation under that contract if the failure to obey the law was the proximate cause of the loss. -- Tom H
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