Grounding a generator

[toller]

No typo, stupidity. They also put three 20a circuits on a 50a breaker. I replaced the #10 with #12, and put each 20a circuit on its own 20a breaker.

[HorneTD]

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

[Bruce in Alaska]

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

[Ignoramus25975]

Thanks, that's interesting.

i

[toller]

I've seen this "IgnoramusXXXXX" stuff for years. What is the story?

[m II]

12 with 10..

mike

[SQLit]

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.

[m II]

This may help things..

[Ignoramus25177]

I completely agree and will do it by the code.

i