# Bonding in large industrial facilities



## splatz (May 23, 2015)

Related question on a much smaller scale. Should you put a bonding jumper between the hot and cold at the water heater? I have seen this debated but never to a clear win. There are usually a number of arguments that don't really hold water (i.e.: the grounding electrode system must be continuous) but it boils down to, how likely is likely? 

In your basement screw it can't hurt and even if I didn't think it made sense, who wants to argue over $3 in parts and scrap wire. In your plant, well, it's not so easy to go along...


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## Peewee0413 (Oct 18, 2012)




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## mburtis (Sep 1, 2018)

@Peewee0413 we do have those on some of the flow meters, the mag meters mostly. I don't think I could guarantee that the pipe is bonded back to the grounding electrode system with any confinidence though.


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## mburtis (Sep 1, 2018)

@splatz ive never thought about it that much but don't the pipes screw into the metal tank so they should be bonded together through that? Sure there is tape on the threads but it gets smashed out of the way anyway so I would think it would still make contact.


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## CraziFuzzy (Jul 10, 2019)

The larger the piping system, the likely more continuous the conductivity. Welded pipe, bolted flanged connections, and threaded fittings all conduct just fine, and what gauge 'ground wire' do you thing those 14" chilled water pipes are equivalent to?

The system bond points end up typically being the EGC on the pumps.


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## Almost Retired (Sep 14, 2021)

I would say that much piping, resting on and going through concrete, bolted flanges, water filled, connected to tanks on slabs, etc. etc. It is ufer bonded at the very least.

When was the last time you heard of anyone getting shocked (even a small static charge (not counting from yourself which if it happens it proves they are bonded)) from any of the piping or tanks ?


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## mburtis (Sep 1, 2018)

So that was one of my thoughts, there is an EGC running to most everything, and most everything is a metal case connected to the pipe with a threaded or flanged connection. The small threaded connectors I have no issue saying they are bonded, the flanges that a bolt screws into a threaded flange I have no issue saying those are bonded. However I'm not sure if I could say that the flanges with a through bolt and nut are bonded when your dealing with the thick epoxy paint that they spec on everything around here.


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## Almost Retired (Sep 14, 2021)

If the bolt is properly torqued, wont it gouge through the paint ?


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## mburtis (Sep 1, 2018)

Almost Retired said:


> If the bolt is properly torqued, wont it gouge through the paint ?


You would like to think so but I've taken apart connection that don't show much damage to the paint. Some of this stuff is like an 1/8 layer as hard as concrete.


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## Almost Retired (Sep 14, 2021)

ok ... so now you are relying on the water inside the pipe ? 
In other words, i cant imagine where grounding/bonding is a big deal in an industrial site (assuming proper initial construction of course)
I watched an addition to my mill in 2000. all building steel, mats and under ground grounding conductors were bonded and cadwelded.
if properly constructed, i find it hard to believe an industrial site would have issues


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## 460 Delta (May 9, 2018)

mburtis said:


> @splatz ive never thought about it that much but don't the pipes screw into the metal tank so they should be bonded together through that? Sure there is tape on the threads but it gets smashed out of the way anyway so I would think it would still make contact.


If your home is plumbed in with copper pipe, you’d best use a die-electric unions. The top of the heater will rust out in 5 years if you don’t.


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## mburtis (Sep 1, 2018)

So what brought this back to the top of my mind was this. The other day i noticed a transformer down in the pipe gallery with a bare copper wire running out the back of it and not connected to anything. Upon further investigation sure enough it was the building electrode connection for that transformer. You can see where it used to run over to one of the metal inlet pipes. However 10 years ago or so this plant went through several years of upgrades that included replacing a lot of the big piping with plastic. I'm sure this transformer bond was disconnected then because the pipe is no plastic. That got me to thinking "well I need to hook this up to the building electrode system" then as a stood there looking around with a dumb look on my face I thought "how in the hell do I know what is part of the electrode system and what isnt". 

The original plant was built in the 60s with I'm guessing an ungrounded 240v service (since we still have to 240v ungrounded system) and a major addition was done in the 90s, and then the service was changed to 480 10 years or so ago along with more additions. I know newer parts of the plant have ufer grounds, it's anybodies guess what going on in the old section of the plant. 

What about metal roof steel sitting on top of block walls? Typically would there actually be a wire that runs up and bonds it or is the fact its in contact with the walls enough?


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## Almost Retired (Sep 14, 2021)

One of the mills i work in has an ungrounded 480 service, the bare messenger of the arial quadraplex is not connected at either end from the poco transformer to the first OCPD/disconnect
However i have seen more than one place where building steel is cadwelded to a GEC going down thru the slab. On top of which concrete conducts.
There for the building is grounded/bonded even tho the service is not. The various panels etc. are bonded to the building.

The secondary purpose of grounding is to prevent an accidental difference in voltage between what you stand on and what you touch. The primary is for short circuits of course.

Yes the loose transformer wire needs to be connected, preferably to building steel

If the roof you mentioned does not connect to another portion of roof that connects to building steel, then Yes it needs bonding

is this the answer you are looking for ? or did i miss it?


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## SWDweller (Dec 9, 2020)

I was the maintenance electrician (along with 3 others) for a central plant for a university.
Plant was built in the late 40's, meaning it had been remodeled several times. We found a transformer with a 250 mcm going into the concrete floor that had no relationship with ground. 
Tested by an AMEC 3731. A re-pipe job was going on with the 36" welded chilled water pipes. We found a lot of not funny goofy ground readings. Not really concerned as most of our equipment at that time was not electronic, but relay based. We investigated cad welding and found that the ability to weld on big pipes was limited. The Burndy guy showed up for another reason and brought us the compressive grounding fittings and the battery tool. There were fittings for the edge of an eye beam. Also ones with 1" holes so we could do the pipe flanges, as well as a ton of water bond clamps, city water, clean water, chilled water, DI water, soft water to name the easy ones. Then there was the hot water systems and compressed gas piping. Very few of them were in anything other than metal.
We ended using 8 2" 30' long chemical ground rods connected by a 4/0 ring around the building. Then we installed bonding wires in 3 places inside the building for the piping systems. Most will say doing it 3 times is a waste. We decided that 3 times allowed someone to open a system for repair and or upgrading and still have the remaining piping stayed grounded. I took over a year to get the materials, run the bare cables and get the piping systems bonded to the building. 

This building was constructed on old river run, mostly sand and some select boulders the size of a beetle. (the car) Using the AMEC we found several buillding were there was no earth ground. I noticed one ground rod and pulled it out with one hand. Having a tunnel system was no help as everyone that worked on campus thought the water pipes were a ground electrode. When I took them into the tunnel and showed them the water never touched earth until it go back to central plant. Could be 1000's of feet depending on the building location. I spent 10 years there and got into every substation twice. We had an grounding system when I left.


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## mburtis (Sep 1, 2018)

The entire plant is block walls with metal truss roof. I would have to investigate to see if there is a bonding jumper from the roof down to tie into the grounding electrode system. Reason I thought of the roof is that there is another transformer that is using the roof as it's grounding electrode connection, BUT what if the roof really wasn't part of the electrode system... 

These are the spiralling rabbit holes of doom my brain sends me down when I'm at the plant all by myself. 

As far as the transformer with the missing electrode bond, if I go down the wall 10 or 15 feet the pipe is still the original metal so I can bond it there. Now this pipe runs through the wall outside and through the ground for a ways. So it would definatly qaulify as a grounding electrode... BUT since the pipe transitions to plastic inside the plant I'm not sure if there is an intentional bond back to the other grounding electrodes in the plant or not.


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## SteveBayshore (Apr 7, 2013)

On the many water treatment plants that we have done, we only hit the process piping once with our UFER conductor. Have never seen or installed anything additional.


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## Almost Retired (Sep 14, 2021)

I would think there is some sort of metal/rebar holding the roof to the walls. However that will not be a part of the GEC system, there for not a good bond

I have heard of and seen situations where an ungrounded metal roof can accumulate static voltage. It will bite if it does, but it will usually be static only.

Personally (in the situations i am familiar with, cant answer for you) i wouldnt worry about the roof until it causes an actual problem


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## mburtis (Sep 1, 2018)

@Almost Retired like i say the only thing that made me question the roof was that a transformer is using it for its grounding electrode connection. If it wasn't for that I'm not sure it would even be required to be bonded. I guess that comes down to whether having conduit and lights attached to it makes it likely to become energized or not.


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## Peewee0413 (Oct 18, 2012)

mburtis said:


> You would like to think so but I've taken apart connection that don't show much damage to the paint. Some of this stuff is like an 1/8 layer as hard as concrete.


There's a reason through hole bonding requires grinding the surface.


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## Almost Retired (Sep 14, 2021)

so if you have conduit on the ceiling, it is the grounding path for those circuits, or the EGC inside it is. bring a pigtail out of a junction box or ceiling box and connect to the steel.

Probably not code but better than nothing. An EGC is not intended to be part of the bonding system and is also not large enough, but it would prevent static charges, etc
however it could cause a problem if a poco conductor (or something else with large fault currents) gets dropped on the roof and the short circuit current burns up all the wires in that conduit. Very long shot im sure, but just as an example of worst case

as for the txr, i would hope it already has an EGC in the feed to it. If not then it is old school and they are using the conduit for egc. That wont completely get rid of the voltage difference between it, and where you stand to work on it, unless it is sitting on the concrete you would be standing on. In which case , no worries 

Another idea about the abandoned wire on the txr, they may have been borrowing the txr's ground for something else that was removed a while back. Possibly that pipe you mentioned, it may have had a sensor on it that was misbehaving due to lack of grounding


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## mburtis (Sep 1, 2018)

Both transformers I mentioned have EGC ran with the primary feed, and both are sitting on the concrete floor. Although now that I think about it the EGC for the one is disconnected in the MCC. I forgot I still need to hook that up. Sometimes this place is like trying to keep a leaky ship afloat with a teaspoon. I'm betting that the pipe fitters unhooked the electrode bond for the transformer when they tore the old pipe out and it never got hooked back up to anything.


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## splatz (May 23, 2015)

mburtis said:


> @splatz ive never thought about it that much but don't the pipes screw into the metal tank so they should be bonded together through that? Sure there is tape on the threads but it gets smashed out of the way anyway so I would think it would still make contact.


Maybe it would, maybe it wouldn't, now or later. Same answer if someone asks isn't hot bonded to cold at the faucets. Dielectric unions, plastic stuff, sharkbites, just general bad connections, I don't know. Lots of things could happen that the jumper won't help, but it will help some of them.


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## gpop (May 14, 2018)

I can lend you a welder that will test your bonding system. Hes great at finding any bond that wont handle a 120 amps.


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## splatz (May 23, 2015)

mburtis said:


> The entire plant is block walls with metal truss roof. I would have to investigate to see if there is a bonding jumper from the roof down to tie into the grounding electrode system.


In a lot of commercial construction, 250.68 allows you to use the steel itself as a conductor. So you usually see the GEC for the secondary side of the transformer just goes to the nearest i-beam or column. I definitely don't think a block building with a metal roof satisfies that requirement. I see those jumpers run to anything metal at all, all the time, and it passes, but I can't connect the dots to see how it is compliant in many of those buildings, like yours. It's not enough that the metal just have decent contact with earth. 

Also in 250.68 - the water piping can be used the same way, up to 5' from where it enters the building, or farther in industrial buildings like yours - as long as it's exposed. I think this implies, but doesn't explicitly state, that you should be able to visually inspect the pipe and make sure electrical continuity is maintained, which would mean jumpering around the meter or etc. 

_Exception: In industrial, commercial, and institutional buildings or structures, if conditions of maintenance and supervision ensure that only qualied persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a bonding conductor to interconnect elec‐ trodes that are part of the grounding electrode system, or as a grounding electrode conductor, if the entire length, other than short sections pass‐ ing perpendicularly through walls, oors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed. _​


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