To bond or not to bond neutral and ground in new electric service panel?

[buickanddeere]

The ground system is not expected to trip a supply breaker every time something live touches it. The ground system's function is to hold everything connected to it as close as possible to true earth potential. To reduce step voltage and touch voltage around electrical failures for people and animals.

 

[3Ts]

There is value in hiring an licensed electrical contractor and taking out permits, and having final inspections. Just my two cents. Bob

But only if he knows what he's doing! I have one that put in a multiwire circuit with 12/3 from the attic to the kitchen island. He then ran 12/2 from the attic to the main breaker panel. Each side of the 12/3 draws 15 amps (a dishwasher on one side and a 120v water heater on the other side). He put in a single 20 amp breaker and tied the red and black together. I told him he needed a 12/3 with a bonded breaker. He put in a doubled up breaker and connected the black wire to one terminal and left the other open. Wrong! Then he wanted to put a 30 amp breaker on the 12/2 wire. Wrong again! I repeated that he has to run the 12/3 wire all the way to the main panel - he said he can't do that. (This is new construction and was pointed out before the wall was closed in. They closed it in anyway.) I'm refusing to accept anything that's not right on this circuit so it's going to be an issue with the builder, cause he's going to have to open up the wall, dig out the spray foam and run the 12/3 wire.

 

[dweitzel]

MossRoad has it covered. Give the AC dude a cussing for connecting the ground to the neutral bar. Did you purchase the QO panel with the built in generator transfer switch ?

Buick, no I bought the larger 52 space QO panel. The Kohler generator transfer switch is outside, and outdoor rated and sits near the generator and meter base approx 220' from the building.

 

[buickanddeere]

Buick, no I bought the larger 52 space QO panel. The Kohler generator transfer switch is outside, and outdoor rated and sits near the generator and meter base approx 220' from the building.

Sounds like a good system with proper design and installation. My Square D transfer panel wasn't really planned. I have a 200 amp transfer switch outside at the main service. However the main breaker failed in my old undersized 200amp FPE stab-loc. panel. For all the difference in price between the SQD with and without the transfer, installed the transfer unit anyways. 42 circuits with 40 used.

 

[CobyRupert]

The ground system is not expected to trip a supply breaker every time something live touches it. The ground system's function is to hold everything connected to it as close as possible to true earth potential. To reduce step voltage and touch voltage around electrical failures for people and animals.

Yes, it should trip if it’s a grounded system, example: from a grounded transformer, or grounded wye, or center tapped transformer. That’s why the neutral is bonded to ground rods and the ground system (the green wires), so that there is a low impedance (resistance) path back to the neutral of the transformer and a large short circuit fault current develops that trips the breaker.
There are unique systems, for example a transformer with a “delta” configured secondary that is ungrounded, or a “wye” transformer that has a high impedance grounding resistor that limits ground fault currents to a level that won’t trip the breaker, but these are rare and usually only seen in industrial or utility settings.

 

[prichard]

The ground system is not expected to trip a supply breaker every time something live touches it. The ground system's function is to hold everything connected to it as close as possible to true earth potential. To reduce step voltage and touch voltage around electrical failures for people and animals.

Really? Granted it's been a while since I was licensed but every code book I've read specifically says propose of grounding is to make breakers trip. IIRC it says something along the lines of "to facilitate the operation of over current protective devices". I don't recall any where in NEC that says it is to keep things close to earth potential or about step voltages.

 

[Tractor Seabee]

DYIerrs: Beware, there is a lot of misinformation in this thread and a lot of dangerous practices touted as gospel. I do not have the energy to go through this thread and spot all the bewares. There are plenty of resources out there; Big box stores have some good ones, get some before you start and follow that, not what some armchair expert says. Article 250 (Grounding and Bonding) does not always explain theory behind the requirement. It is assumed the NEC user has adequate theory already in their brain locker. Grounding and Bonding is considered the most mysterious of all the rules. Many electricians, especially the self trained ones can be dangerous.

Apprentice and Journeymen training classes rely on a text book called "SOARES Book on Grounding and Bonding". It is available on Amazon I believe under $100. It bailed me out many times when I was an electrical inspector on military projects. They do not have their own inspectors for contracted work, the contractor hires their own team for all trades. I had it, the referenced code book plus several other manuals and still got caught short and had to go back and review. We did everything from communications up to 115KV distribution. Broad range of experience and I do not consider to be an expert on any of. I spent a lot of my own time reading and researching the night before a new situation. I lost very few arguments on work in place but lost many on my lack of theory training.

The NEC is revised and reissued every 3 years. Most jurisdictions specify the code prior to the current one to give their inspectors time to update. Both electricians and inspectors are not infallible. Some electricians are still working with older code books and inspectors are up on the new. Inspectors, when work is booming do not have time to really look at a job and rely on electricians they know to do it right.

Ron

 

[California]

Thanks for emphasizing the importance of getting it right.

Home Depot, Sunset, etc publish DIY books. Are there any at moderate cost that might be sufficient for a single DIY remodel project that would pass inspection?

 

[Tractor Seabee]

I will be starting a project soon. My old code books are long gone. I will check out what Lowes has probably next week and try to give my opinion on what I get to help me with current code and report back. Remember those books are somewhat generic and not necessarily in tune with local inspector interpretations. Mine is a generator. There is more than one opinion on such a system called "a separately derived system" about earth grounding of the generator. That has changed over the years. Stand alone portable generators used in the field are another subject covered under the OSHA Safety codes; used for building emergency power is the NEC.

LOL, Ron

 

[buickanddeere]

Really? Granted it's been a while since I was licensed but every code book I've read specifically says propose of grounding is to make breakers trip. IIRC it says something along the lines of "to facilitate the operation of over current protective devices". I don't recall any where in NEC that says it is to keep things close to earth potential or about step voltages.

Well admittedly I could have and should have explained that better . This is why all the ground rods/plates for the main service and sub panels should all be bonded together with a dedicated ground cable and on bojdnto neutral made at the utility service . Overhead supplies with a triplex cable cause some complications .