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How do I safely ground a sub-panel when it's impossible to do it correctly?

How do I safely ground a sub-panel when it's impossible to do it correctly?

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  #1  
Old 02-03-15, 04:22 PM
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How do I safely ground a sub-panel when it's impossible to do it correctly?

So I have a sub-panel on the back-side of my house that is fed from the main panel. I always assumed that there was a ground wire that ran from the main panel to this sub-panel, and just recently discovered that there ISN'T. This sub-panel has its own ground rod, and is wired with the neutral and ground sharing a bus-bar.

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I know this is an absolute no-no :NO NO NO:, and that the only place the neutral and ground should connect to the same bar is at the main panel. But with no ground connecting the panels together, does that rule still apply?

Unfortunately, it is basically impossible to run a ground wire from this sub-panel (which supplies half of the house) back to the main panel without tearing out absurd amounts of drywall and/or concrete.

Without being able to do it correctly, what options am I left with? What are the dangers of leaving it like it is (it's been like this for 15+ years) and is there anything I could do that would make it better/safer short of remodeling my entire house and getting a ground wire from the main to the sub? (My cold water pipes are PVC so that trick won't work either.)
 

Last edited by PJmax; 02-03-15 at 05:41 PM. Reason: corrected coding
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  #2  
Old 02-03-15, 04:25 PM
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Do you have a cable or conduit between panels? If conduit, what kind of conduit?
 
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Old 02-03-15, 04:29 PM
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No, the wires (older ones with silver insulation) just disappear into the wall and pop out from a wall on the other side of the house. No conduit.
 
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Old 02-03-15, 04:50 PM
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Can you take pics of these cables ? Seems odd to have (CABLES) for a sub feeder.I can't view what you have sent.

Geo
 
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Old 02-03-15, 05:09 PM
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You can only see two in the pic, but there are three of them there emerging from that old silver insulation. They are large ... I want to say #1 or #2. And aluminum, not copper. Really old Romex? http://images.ibsrv.net/ibsrv/res/sr...s/confused.gif
 
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Old 02-03-15, 05:36 PM
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That is old cloth covered service cable and it's most likely silver plated copper based on the age. That would be a normal sight between panels.

What are the extra cables that shouldn't be sharing the knockout with the service cable ?

In the past this may have been grandfathered in. Now it looks like the service cable is in need of replacement.
 
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Old 02-03-15, 06:10 PM
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The white Romex is abandoned, the black is a live circuit.

Yes, in an ideal world I'd replace the entire service cable, but---just like with adding a ground---that would require tearing open many walls and/or tearing out concrete. And to be honest, if I could afford to do that, I'd be living in a newer house that DIDN'T have old/hinky wiring

So at this point I just need to know what I'm risking by having the sub-panel wired as it is, and if there is any way to make it better/safer with the means at my disposal...which pretty much negates adding a ground between the panels or replacing the service cable altogether.

Thoughts? Ideas? (pity?)
 
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Old 02-03-15, 06:21 PM
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Not an electrician, but curious if the abandoned white romex - or a portion of it could become a ground. That would also assume that the other end is at the main breaker box. Probably not legal, just a thought.
 
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Old 02-03-15, 07:22 PM
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Nice thought, but no, it's a very short piece of abandoned Romex. The total run back to the main panel---best I can tell---is nearly fifty feet
 
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Old 02-04-15, 07:31 AM
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Your subpanel feeder was legal in some parts of the US until the mid-2000's, so it is OK to leave it as-is grandfathered under an older code. Some things you couldn't do with the panel would be to install a new hot tub, pool, cooking range or cloths dryer from it. You can continue to use existing circuits that are already installed. You could install new receptacle or light circuits from this panel.

The biggest danger with this type of installation is that the neutral (probably a braided bare wire) becomes loose, damaged or corroded at the terminals. Without a separate ground to serve as backup, circuits connected to the subpanel can develop shock conditions once the feeder neutral is deteriorated. If you give this panel a good inspection to make certain the neutral is in good shape and well connected on both ends, there won't be an issue.

For better lightning protection it would be best to disconnect the ground rod from the subpanel. Your house should only have a single reference to the earth at the main panel. Additional ground rods that are not connected the right way actually make the grounding worse than having none at all.
 
  #11  
Old 02-04-15, 08:28 AM
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If both panels are on outside walls getting a new subpanel feed isn't that hard.

(A) Fasten conduit to the outside of the house from one panel to the other.
(B) Run conduit down the outside wall, bury, and up the wall at the other panel.
(C) Run conduit protected cable up the outside wall, across the attic (no conduit needed), and (conduit protected) down to the other panel.
 
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Old 02-04-15, 08:37 AM
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Thanks, that's very helpful information

As for disconnecting the existing ground rod at the sub-panel: I'd heard that there should never be more than one ground-rod per structure. Is that correct?
 
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Old 02-04-15, 08:55 AM
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There should be single point grounding between all of the electrical systems (power, phone, cable, antennas etc) in a building. There can be multiple ground rods (two is common) or other earthing means, but they all must come together at one point by connection with a heavy copper wire before being bonded to any other system, including the power panel(s).

You should not have multiple grounding methods spread out across the building. It can cause many issues both cosmetic and serious.
 
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Old 02-04-15, 09:31 AM
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Ray2047, these are all good suggestions and for any semi-normal situation I'd agree with you.

But:

(C) There is no attic...all open beam. Very nice looking and all, but it provides zero options for a mechanical chase.

(B) At some point someone decided it would be a really good idea to put wide concrete walkways pretty much around the whole perimeter of the house, so no digging.

...and I put this one last because it is the most annoying of all: http://images.ibsrv.net/ibsrv/res/sr...milies/mad.gif

(A) They covered the entire house in Sears Vinyl Siding, under which lies a layer of 1" rigid foam board glued to the preexisting stucco. The siding is affixed by nails just stuck into the foam board, and every eave, windowsill, door, spigot, doorbell, etc. on the outside of the house is sealed in little glued together custom fitted vinyl trim abominations that are impossible to take apart without destroying.

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Oh, and you can't get any of the raw parts to re-do them yourself...you have to use an Authorized Sears Vinyl Siding Installer. This means that modifying anything, or permanently attaching anything to the outside of the house is almost impossible...unless you want to pay someone else to cut and glue little bits of plastic together.

Sears Vinyl Siding = DIYer's nightmare http://images.ibsrv.net/ibsrv/res/sr...milies/eek.gif
 
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Old 02-04-15, 10:41 AM
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Can't you put the conduit on top of the vinyl? Use long screws to fasten to the sheathing under the siding.
 
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Old 02-04-15, 11:08 AM
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Do you have exposed foundation wall?
Geo
 
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Old 02-04-15, 11:19 AM
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The offending siding is made to look like horizontal ship-lap, but in reality it's just a flimsy facade ... the "lap" part that protrudes has nothing behind it but void, so whenever you try to screw anything to it, it just crushes it in.

The stuff really is horrible in almost every way. http://images.ibsrv.net/ibsrv/res/sr...ilies/wall.gif

(the only exception: it's fire resistant. When I can afford it, I'm going to tear it all off and replace it with Hardie)
 
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Old 02-04-15, 11:27 AM
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"Do you have exposed foundation wall?"

At certain points yes, other places no. There are several decks, big built-in planter boxes, and a number of other obstacles that would make running conduit around the entire structure a logistical and aesthetic nightmare.
 
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Old 02-04-15, 04:45 PM
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Is the meter in or on the same building as the second panel?

That trim piece around the hose bibb is easily available in the big box stores.

https://www.google.com/webhp?sourcei...0trim%20blocks
 
  #20  
Old 02-04-15, 06:53 PM
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It's actually more complex than that diagram I put in the original post: The meter and main is on another building, and is grounded properly there. Then it runs (with a ground) to a secondary panel (properly bonded with neutral and ground separate) on the house, from which two more sub-panels run, neither of which have a ground wire running to them. One is inside the house and really close to the secondary panel so I can get a ground wire to it. But the other is pretty far away and is the one with ground and neutral connected, in addition to having its own ground rod.

And looking at the link you sent (and following where it led) it does appear that it is possible for the general public to get all the various parts to do the vinyl siding thing. Thanks for that

However, at this point I've just come to hate the stuff so much ... it absolutely kills me to think of buying it and actually working with it.

But it looks like that may be what I need to do .... http://images.ibsrv.net/ibsrv/res/sr...ilies/cool.gif
 
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Old 02-04-15, 07:12 PM
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Arlington also has very nice siding boxes for fixtures, meters and receptacles.

Arlington | Quality Electrical Products and Fittings
http://www.aifittings.com/catalog/siding-mounting-blocks/
 
  #22  
Old 02-04-15, 07:15 PM
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Most vinyl siding can be unzipped at the bottom* and folded part way up. You could run a ground wire underneath where the hollow is and snap the siding back in place. Better cut a channel in the foam for " PVC to run the ground only in.

*They make tools to unzip the siding. Example: https://www.google.com/search?q=viny...30025269805878
 
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