Grounding Requirements for Multiple elec. power Services in same building

Refer to your local electrical standards and regulations. All the requirements relevant to your country and site are clearly stated in them. If you don't have a copy of them, you need to get one.

Complicated question. Answer depends upon where in the world you live. Which is where?

Oh sure. My local electrical code clearly states only one grounding point to be used at the main service entrance. ALL sub-panels fed from that single main service entrance MUST not be fitted with additional grounds rods or plates. In fact all breaker panels come equipped with a brass grounding screw that ties the metal box (and the ground) to the neutral common bus. A tag notice is affixed reminding the installers to remove these screws when the breaker panel is used as a sub panel fed from the main panel. However the local inspector made the licenced electrician add a ground plate to every sub panel ( total of 12 ) fed by the main panel. WHY?

The inspector is contradicting the code book.

Maybe the inspector needs to go back to school! what You state also applies in the US.

oilcan13

Hi Elnav... please accept my apologies for not having responded to your email request for info on this subject. I have sat down twice to do so, but, each time I have been side tracked by something.

What you have described is in fact what is required under the Canadian code. Plain and simple, unless there is a code amendment in force in that jurisdiction, that inspector is wrong. Unless... there is livestock being housed in the buildings.

If that is not the case, you should have taken it up the food chain to the person's boss. As inspectors, we do not have the power to require things that are clearly not mandated by the code in effect in a jurisdiction.

Was this in BC? If so, why not write me up a formal letter detailing all that happened and I will pass it on for you to the powers that be for their comment. The Chief Electrical Inspector in that province is an acquaintance of mine.

Writing a formal letter would open a can of worms. The camp is a Bible study camp. Volunteer electricians from the churches normally employed elsewhere often do the electrical work. Permits are usually pulled but have not always been done in the past.

I have no standing in BC as far as certified electrical work goes. BC simply does not recognize my Ontario CET standing etc. I don't want to cause a problem for the camp or my friend. I can inspect everything and quietly recommend all deficiencies be upgraded without getting inspectors involved. Not to mention which critizing the only inspector here may antagonize him.

I worked for a power utility in Ontario and part of my job was to measure ground rod integrity of all utility poles and service entrance ground rods. Because of my back ground I am advising my friend who manages the camp as to what needs upgrading. But because of my lack of certified standing I can't act officially. A new cabin was erected and the inspector berated the electrician who pulled the permit for an improper ground at the cabin which was located about 150 feet from the main electrical service building. The inspector insisted on a plate instead of a rod. As I read the regs, only a ground plate or rod located at the main electrical building is required. In fact there at two rods, both tied to the same point inside the metering cabinet. But all the old cabins have ground rods. Was this a requirement back in the fifties?

Since two more cabins are planned this subject is likely to surface again.

Elnav,

Over the years, the codes have increased their emphasis on separation of the ground and neutral. For years, the frames of electric ranges and dryers were allowed to be bonded to the neutral. Then for mobile homes they couldn't; and now for all new construction they can't. Similarly, separate structures on the same premises were allowed to be locally bonded between the neutral and ground, but now must have their ground and neutral independent. It gets to be a gray area about requiring an earth-connected grounding electrode at each separate building, while maintaining a grounding electrode back to the main service that feeds each building. If you view this as a desire to have the lowest possible potential between the electrical ground and the physical points where a person can contact the ground (such as a metal building frame or metal pipe), then the additional electrodes are reasonable. All you are doing is increasing the number of parallel paths by which electricity (in a fault situation) can be kept from harming the people or the property while the equipment supplying it is clearing the fault.

--John M.

That sounds reasonable. The historical view also supports what I have seen. The earliest buildings were apparently done back in the sixties. Atco dormitories added sometime in eighties or maybe nineties. I removed as much aluminum wiring as I could. Made darn sure the remaining aluminum conductors (over head from transformers and pole to pole service feeds to cottages was properly pasted with anti oxidants and the connection lugs were suitable Al/CU compatible. With the continued expansion over the decades, I was concerned about over loading. I had the older rusty 60 Amp pony boxes removed and replaced with brand new Square D 100A boxes after making sure the major distribution feeders were adequate for the load. Each cabin and bulding is still limited to 60A service entrance. I did load checks with a clamp on meter as well as IR thermal scans under heaviest load conditions and everything is still running at less than 50% loading worst case.

Sounds to me like you have done a good job with this by advising and helping the guy who took out the permit. The church group is lucky to have your assistance.

Thanks! My friend worked in property maintenance for 15 years before moving up here. Between the two of us we are making major improvements. Last summer we rebuilt the water system with a submerged pump out under the lake and a fire main buried well below the frost line. This means there is now pressurized water even in winter and the main pipe is now large enough to serve as a fire main. And all risers to the buildings now have heat trace cable installed. We are now planning on a back up emergency generator. Winter storms often take out the line when trees topple and it takes days to repair. I got him to rebuild the closet housing the main electrical panels into a proper metering room 6' X 8' and locked so it doesn't get used for storage. He put on a new roof and a new floor. If and when we get an emergency generator, it will have its own building next to the metering room. There is room for a proper code approved transfer switch. None of this Walt Disney engineering of plugging into a dryer outlet and reverse feeding the house panel, like so many ranchers out here do. Yikes!

True and valid points.

However, the choice of increasing the safety of the installation, above minimum code requirements, by the addition of extra ground rods, is one that is in the domain of the property owner and not that of the inspector, who has a published prescriptive code to enforce.

To minimize ground loops (which can occasionally be life threatening ) all grounds need to go back to the ground at the main feed. If you use more than 1 ground rod they should always be tied together before they attach to the main feed for the same reason. Electrical codes can differ on the fine points, but I've never seen any codes that differed from the first 2 statements. Please check this with your codes to be sure.

Agree completely.

Also... the most important reason this is done is to ensure that the "bonding system" that is created at each separately derived system, is at the same potential as the next "bonding system" during fault conditions.

The impedance back to the source on a bonding system can cause an impressed voltage on a bonding system during fault conditions relative to the bonding system of the next separately derived system. Connecting them together ensures that won't happen.

This is the best answer. One premises may have different services & Separately derrived systems (Transformer, Generator etc.) but the bottom line is all grounding and bonding in a premises shall be in tied one grounding system to make zero potential among all grounded systems of all services.

Hello kamaig,

Your request is one where it is crucial to know what Country you are talking about. There is basic bonding requirements on a single dwelling and multiple dwellings in a block.

..................I am not referring The bond must always be continuous from flat to flat and, floor to floor.

All the multi-dwelling blocks should be grounded (earthed) on a cold water pipe. That will always go direct to ground and hence (earth).

Care should be taken NOT

to connect or bond the Earth cable to the hot water or any other water that may not go to ground!

babybear, I am concerned with your post.

Water pipes are NOT used as a ground electrode, cold or hot, in the modern day.

The code requirements involving bonding of (not grounding to) water pipes is for the protection of life in the event of an appliance failure etc that energizes the pipes.

There is no way to insure that a section of a piping system will not be opened (as during plumbing repairs) or that sections may be plastic, and therefore are specifically NOT used as the protective earth connection.

The reason for requiring a bond from the protective earth wiring system to the metal pipes is to protect the pipes, not to add to the protective earthing system.

I was called to a house to find out why the water tap in the kitchen was giving electric shocks. Upon arrival I found full strong line to neutral voltage between a metal window frame and the wet grass in the yard.I found that the incoming water main was plastic up to the first valve. The electricians had used the metal piping under the house as his earth electrode, and in addition some workman had driven a nail into one of the house circuits through the 'chicken wire mesh' of the stucco (plaster). The result was elevating the entire metal of the house, including the metal piping, to line voltage as respect to earth.

After locating & correcting the fault, I drove a ground electrode into the earth and connected the main panel ground buss as per US code. In the future any shorts will trigger the protective devices.

As to your comment about not bonding the hot water, a separate bond to the hot water is proper to also protect it from accidental electrification, since it is usually isolated by non-corrosive or galvanic fittings at the water heater.

Search this site, there have been several extensive discussions about this.

Regards, CJMcGill

Hello CJM,

As a little background .................... up until about 15 years ago all pipe were steel, or lead, but mostly copper, including the cold water mains feed. The electric earth or ground was always bonded to the cold water feed just above the soil. That has been the general rule in any houses I have worked on and in.

I fully agree with you that the rules and regs' have maybe changed since I last did any work on a house professionally. But when working on an all copper fed house, I/we always turned the power off when doing any plumbing. There was no need to use power tools at the precise time the plumbing was worked on. Any fixing of pipes was done after the power was back on. .........It is the way I/we worked.

I fully understand that since the use of plastic pipe there must be a completely separate bonding system.

I cannot recall what I said in my post now, but I think I mentioned about the safety aspects.

Hello CJM,

Thank you for your understand and kind reply post. I respect you and was glad you got back to me, thank you.

I think internal plumbing of plastic pipe should never have been allowed. It cannot take hardly any pressure and is a nightmare when it comes to "taking for granted"

the continuity of an earthing or grounding source!

Much the same can be said for the use of plastic soil pipes. As I finished working in the industry you could get whole sewer systems in plastic, and with a 'life' of just 20 years, anyone buying the houses built by the firm I worked for, would have to replace them two or three times in the time they may have lived there? I think it a disgrace. And a huge step backwards, when the industry should be taking steps to make buildings more safe and reliable, not the opposite.

Take care my friend.

• British Standard 7671.
• Indian Standard 3053.
• Etc.