ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Extension cords
by LongRunner. 05/25/18 12:19 PM
Fire source!
by LongRunner. 05/25/18 01:49 AM
Alternative income sources
by gfretwell. 05/24/18 10:07 PM
Furnace igniter leaking noise to stereo
by geoff in UK. 05/23/18 01:18 PM
Opinions Please
by Keith_Mc. 05/23/18 09:22 AM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
2 registered members (ampherder, geoff in UK), 29 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 3 1 2 3
Is this safe? #219268
04/25/18 06:21 PM
04/25/18 06:21 PM
T
twh  Offline OP
Member
Joined: Mar 2004
Posts: 940
Regina, Sask.
Our inspectors are going to enforce new rules about grounding and bonding. It strikes me as wrong because we are moving back 40 years to when I started in this trade. The problem only applies to buildings with a metal water supply and metal internal piping – most buildings that might need a service upgrade.

40 years ago, (when I started) the neutral was grounded to the nearest cold water line and the meter was jumpered to maintain the ground if the water meter was removed. City employees were reportedly getting shocks when they changed water meters.

When plastic water lines became popular so a plumber might replace a section of copper line with plastic, we grounded to the street side of the water meter and bonded the inside copper lines.

Now, we are to ground the neutral at the top of the mast. The ground wire runs to the meter socket where the socket is bonded, and continues to ground rods or a ground plate. My understanding of this type of ground is that it will have a resistance of more than 10 ohms, and a lot higher when the ground is frozen.

From the meter socket, the panel is bonded. The closest cold water line is bonded to the panel. So, the neutral is electrically connected to the water line, but we now call it a bond.

The jumper across the water meter is to be removed.

My issue is that I have a metal water meter. I isolated it and it clearly has 0 ohm resistance across the meter. Removing the jumper doesn't stop electricity from flowing through the meter.

In the future, if we lose an overhead neutral from the poco, the return path will be through the water line, through the meter and through the incoming water line which is bonded to neutral in the neighbor's house. If a plumber cuts a line, or a city employee removes a meter, they will break the new return circuit. I don't think being in parallel with a 10 ohm ground rod is going to save them.

What do you think?

Work Gear for Electricians and the Trades
Re: Is this safe? [Re: twh] #219269
04/26/18 02:04 AM
04/26/18 02:04 AM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,225
Estero,Fl,usa
I don't see where much really changed except they don't trust water pipes as being a grounding electrode anymore. I agree back in the old days with solid metal water systems the water pipe was the current path when the neutral opened so breaking that pipe circuit might always present a danger.
These days the Ufer (concrete encased electrode) is rapidly becoming the "go to" grounding electrode and it is part of the footer inspection in Florida, to insure it will be "present".


Greg Fretwell
Re: Is this safe? [Re: gfretwell] #219270
04/26/18 11:04 AM
04/26/18 11:04 AM
T
twh  Offline OP
Member
Joined: Mar 2004
Posts: 940
Regina, Sask.
Originally Posted by gfretwell
I don't see where much really changed except they don't trust water pipes as being a grounding electrode anymore. I agree back in the old days with solid metal water systems the water pipe was the current path when the neutral opened so breaking that pipe circuit might always present a danger.
These days the Ufer (concrete encased electrode) is rapidly becoming the "go to" grounding electrode and it is part of the footer inspection in Florida, to insure it will be "present".


The water line is still a parallel path to the transformer through the neighbor's house. the only thing that changed is that they renamed the "ground" wire as "bond" wire. If the overhead neutral is lost, the water meter becomes the return path. That problem was solved before I started in the trade in 75 and now we unsolved it.

Lets put it another way. Cut the overheat neutral and take the water meter out without a jumper. Does the guy working on the meter get a shock?

We aren't installing Ufer grounds. Where did that come from?

Re: Is this safe? [Re: twh] #219271
04/26/18 01:54 PM
04/26/18 01:54 PM
T
twh  Offline OP
Member
Joined: Mar 2004
Posts: 940
Regina, Sask.
Does anyone know the resistance of two ground rods?

Re: Is this safe? [Re: twh] #219272
04/26/18 01:59 PM
04/26/18 01:59 PM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 6,967
Brick, NJ USA
twh:

"We aren't installing Ufer grounds. Where did that come from?"

I guess that is a difference between Canada (CEC) and the USA (NEC)

We require a Ufer to be installed on new construction, additions with new footings, etc. Both resi and commercial. The metal water line is becoming a thing of the past.

Yes, we still jump out water meters that have metal supply visible within the structure. It could be plastic out to the street, but who knows.

One POCO does not allow the ground conductor to enter the meter pan, another does. It gets interesting when some ECs work in an area that they are not familiar with.

On the funny side, I occasionally come upon the hot/cold bond at a water heater that has PEX piping. Waste of two pipe clamps and a length of wire.


John
Re: Is this safe? [Re: twh] #219273
04/26/18 05:03 PM
04/26/18 05:03 PM
T
twh  Offline OP
Member
Joined: Mar 2004
Posts: 940
Regina, Sask.
Here is a sketch of two buildings grounded and bonded to our new rules, with the fault path if a poco neutral is broken.


Attached Files
NewGrounding.pdf (25 downloads)
Re: Is this safe? [Re: twh] #219274
04/26/18 10:42 PM
04/26/18 10:42 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,225
Estero,Fl,usa
I am not sure what changed. The service can be grounded anywhere from the service point to the bus bar in the service disconnect enclosure. It is grounded (or bonded) pretty much like it always was. The only reason we distinguish between grounds and bonds is to describe the intent of the connections. The electrons don't know the difference. You have always been using the water utility as your best connection to the utility neutral. We just can't say that. It is like saying my swimming pool is my best grounding electrode. (I don't have utility water)
It doesn't sound right to say that but it is still a fact.


Greg Fretwell
Re: Is this safe? [Re: twh] #219275
04/26/18 10:47 PM
04/26/18 10:47 PM
T
twh  Offline OP
Member
Joined: Mar 2004
Posts: 940
Regina, Sask.
Greg, it isn't the point where neutral is grounded that is the issue. It doesn't matter. Don't get stuck on that. I just show it on the drawing to be exactly accurate.

The point is that if the poco neutral is lost, the system keeps working because there is a neutral connection through the water meters. Then, if the plumber cuts the line, he is cutting the neutral connection.

Re: Is this safe? [Re: twh] #219277
04/27/18 08:58 AM
04/27/18 08:58 AM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 6,967
Brick, NJ USA
OK, I see your points with the sketch and your comment above.

Yes, if the metal water line is cut, the return path is broken, if the utility neutral is 'lost'.

There have been lost utility neutrals, both OH & UG, that sometimes create havoc, and sometimes go unnoticed for some time, all dependent on the earth ground system integrity.

We collectively have to accept that the 'water piping' as an earth ground is becoming a thing of the past with the proliferation of non-metallic water supply piping. IMHO, that is one of the main reasons to install the Ufer system.

I have had a few calls over the years of techs from the water utility getting 'shocks' when changing out water meters. The utility held a safety meeting, and requires their meter techs to look for the NEC required jumper first, and if one is not present advise the owner.
They also have 'temp jumpers' for safety. Yes, we still have 'aged' homes that lack the jumpers on the water meters, and the water heater units.


John
Re: Is this safe? [Re: twh] #219279
04/28/18 02:40 AM
04/28/18 02:40 AM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,225
Estero,Fl,usa
The metal utility water line has always been a neutral path, whether the PoCo neutral is connected or not. Remember current doesn't take the path of least resistance, it takes all paths. The copper water pipe may end up having more circular mils and lower resistance than the 1350 aluminum conductor. Back in the olden days the whole water system was a grounded conductor. This is nothing new. What is new is that water pipe is probably plastic now. That will certainly be true soon if the original was lead.


Greg Fretwell
Page 1 of 3 1 2 3

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
JoeKP
JoeKP
Berkley, MA
Posts: 144
Joined: March 2008
Show All Member Profiles 
Top Posters(30 Days)
twh 12
Popular Topics(Views)
246,909 Are you busy
184,276 Re: Forum
173,508 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.041s Queries: 17 (0.005s) Memory: 1.0312 MB (Peak: 1.2135 MB) Zlib enabled. Server Time: 2018-05-25 18:20:29 UTC