Unique Grounding Question

[MoparTrucks]

I saw on another site (I wasnt a member so couldnt ask questions) where a thread went on and on from a guy who had a separate service to his pole barn about how he "bonded" the metal skin of his post frame pole barn to the grounding rod with #6 AWG (this was in addition to the standard grounding from his service). He went into great detail about how he had cleaned off the paint where the screw attached and didnt use a rubber washer and from the pictures it looked like he just used a standard metal siding screw.

Two questions; has anyone ever heard of this on a post frame building and would it do any good? I just cant wrap my head around what he was doing but it got me wondering since no one else on that site chimed in and asked WTF?

 

[ishiboo]

Not necessary nor code - only metal structures (ie the frame.) I don't see any significant advantage to it.

 

[Mustang51js]

Just a waste of time, and if he ran pipe or installed his panel to any of the metal in the building it would be bonded anyway

 

[MTW]

If it isn't intentionally grounded, you one day, may well wish it was. If that siding is floating (not connected) with respect to ground and becomes accidentally energized from any hot wire, it may kill you or others who touch it while standing on the ground. The ground connection serves to trip the breaker immediately and reduce the risk of shock or fire, in the event that it may become energized.

Here's another scenario. At a home I was troubleshooting, customer was complaining of getting shocked from a range hood in the kitchen. Sure enough put a tester between a gas stove and the metal hood, a full 120V. Examination of the hood and wiring done, nothing found defective. Checked the stove no power coming from there, only ground from the gas pipe. When the hood circuit was disconnected, power remained to the sheet-metal and ductwork. Disconnecting the round duct from the fan, the power disappeared from the hood housing. Putting the duct back on brought the voltage back. It was hard to believe because the duct was just laying in the insulation, foil coated insulation that is.

Turns out that the garage underground had gone bad from a frost heave and poor installation practices. One of the UF garage wires shorted to a conduit sleeve. The conduit ran up to the attic area before entering the house. Where it entered the house it was touching the bottom of the gutter and the aluminum covered fascia board. This energized all of the gutters and downspouts, as well as the foil coated insulation in the attic, from the fascia board nails contacting it.

I could take a wiggy tester and put a lead on a downspout and one in the dirt and read a constant 120V. Not a good situation to have happening. I asked the customer if they were having high electric bills, they said yes about $500 more than normal but thought it was due to an oxygen generator.
The conduit was not properly grounded as it should have been, just a sleeve like a lot of folks do. And since it was touching the siding and gutters, it was heating up the entire envelope of the building, including the foil coated attic insulation and hence the ductwork.

So the moral is just because the code doesn't mandate something, doesn't mean it a bad idea. The code is a minimum standard to protect life and property, not a design standard. If the conduit was grounded or the siding was grounded, it should have blown the breaker right away to alert you to the short circuit. Thankfully in this instance nobody got hurt watering the flowers which were surrounding the entire house where the downspouts were located, or cooking dinner for that matter.

An extra piece of 6 Ga wire to the siding is good insurance in my book, better than nothing.

 

[1grnlwn]

Since the panels are painted I see no continuity between panels, specially with wood frame. Har to say if any real advantage. Less dirt due to static?

 

[sberry]

Its metal it should be grounded.

 

[rockwithjason]

all metal parts likely to become energized must be grounded. if there are cables running near that metal siding then they are likely to become energized. now keep in mind that most jurisdictions will not enforce this, it takes too much time and energy

 

[MoparTrucks]

If it isn't intentionally grounded, you one day, may well wish it was. If that siding is floating (not connected) with respect to ground and becomes accidentally energized from any hot wire, it may kill you or others who touch it while standing on the ground. The ground connection serves to trip the breaker immediately and reduce the risk of shock or fire, in the event that it may become energized.

Here's another scenario. At a home I was troubleshooting, customer was complaining of getting shocked from a range hood in the kitchen. Sure enough put a tester between a gas stove and the metal hood, a full 120V. Examination of the hood and wiring done, nothing found defective. Checked the stove no power coming from there, only ground from the gas pipe. When the hood circuit was disconnected, power remained to the sheet-metal and ductwork. Disconnecting the round duct from the fan, the power disappeared from the hood housing. Putting the duct back on brought the voltage back. It was hard to believe because the duct was just laying in the insulation, foil coated insulation that is.

Turns out that the garage underground had gone bad from a frost heave and poor installation practices. One of the UF garage wires shorted to a conduit sleeve. The conduit ran up to the attic area before entering the house. Where it entered the house it was touching the bottom of the gutter and the aluminum covered fascia board. This energized all of the gutters and downspouts, as well as the foil coated insulation in the attic, from the fascia board nails contacting it.

I could take a wiggy tester and put a lead on a downspout and one in the dirt and read a constant 120V. Not a good situation to have happening. I asked the customer if they were having high electric bills, they said yes about $500 more than normal but thought it was due to an oxygen generator.
The conduit was not properly grounded as it should have been, just a sleeve like a lot of folks do. And since it was touching the siding and gutters, it was heating up the entire envelope of the building, including the foil coated attic insulation and hence the ductwork.

So the moral is just because the code doesn't mandate something, doesn't mean it a bad idea. The code is a minimum standard to protect life and property, not a design standard. If the conduit was grounded or the siding was grounded, it should have blown the breaker right away to alert you to the short circuit. Thankfully in this instance nobody got hurt watering the flowers which were surrounding the entire house where the downspouts were located, or cooking dinner for that matter.

An extra piece of 6 Ga wire to the siding is good insurance in my book, better than nothing.

You know I had never thought of it from that perspective and was thinking like 1grnlwn that since they are painted you wouldnt get much conductivity. I have never seen that done but it piqued my curiosity since it didnt seem to be unknown to the people on the other site (I believe the guy was in Texas).

I guess for an extra piece of mind its another simple project for my own pole barn and I appreciate your taking the time to explain it.

 

[sberry]

I recall a bud that took a general contractor test mentioned a question like this, as I rememberl it called for number 8

 

[ishiboo]

Are GCs responsible for a lot of electrical tasks there?

 

[rockwithjason]

in many places they are required to have a certain amount of knowledge in electrical. it's not uncommon at all for a GC test to have electrical questions on it.

 

[ddawg16]

I find it 'interesting' that after 100 years of using AC power for our houses and businesses, we are still refining the technology and safety.

For example....how long did it take to adopt the Ufer ground?

 

[Mustang51js]

I recall a bud that took a general contractor test mentioned a question like this, as I rememberl it called for number 8

It may have been about the rebarb, which a lot of the gc do when pouring the footings or slab. As far as grounding the siding, if the electric is done right there's no need to ground it and wouldn't be any problems. There's a lot of what ifs in electric and usually caused by electric not done right just like in the story above about the siding on house being energized.

 

[sberry]

What would the electric being done there have to do with not having to ground it.? Its sposed to have a bond, just like was pointed out,, the siding became energized.
As for the GC test, I don't think it was the footer bond although that may be on the test too, all I remember about it was my bud mentioning the siding bond wen he came back from it.

 

[sands35]

It would make sense to ensure a metal skin or roof is grounded if only to control galvanic corrosion.

Proper dressing of wires to protect them from wear and damage is a requirement.

Though when I had the main service installed to my garage the gorillas that work for the PoCo cut off the 3" bell mouth on the PVC riser.

 

[Norcal]

To the OP, was the building "grounded" to a rod or was the rod connected to the grounding electrode system? A rod just driven into the ground is worthless. Mounting electrical equipment to the metal panels will bond it.

 

[sberry]

I read the OP wrong, he said in addition to the service.

 

[MoparTrucks]

To the OP, was the building "grounded" to a rod or was the rod connected to the grounding electrode system? A rod just driven into the ground is worthless. Mounting electrical equipment to the metal panels will bond it.

In the pictures and description he had the standard 8' grounding rod connected to his panel service and then in addition he bonded the buildings siding to the same grounding rod. It was a relatively cheap wood post pole barn with probably 29 gauge galvalume or some such siding and I had just never seen that before.

This was a separate service and not a sub panel as he had a meter on the side of the building. Around here there is so much rock in the ground the grounding rods are usually just thrown in the ditch with the service run (if its underground) and buried and UFER wasnt even mentioned to me when I had my pole barn built.

If it would be another layer of protection it seems like a cheap and easy addition to my own shop.

 

[Mustang51js]

What would the electric being done there have to do with not having to ground it.? Its sposed to have a bond, just like was pointed out,, the siding became energized.
As for the GC test, I don't think it was the footer bond although that may be on the test too, all I remember about it was my bud mentioning the siding bond wen he came back from it.

Because he said the pipe wasn't grounded right and that's why the siding became hot, so if it was done right the first time there's no need to ground the siding,but if the service was mounted to the shell it would be bonded anyway. Also if there's steel inside some towns want a bonding wire to that so it would cover anything connected to it anyway.

 

[Mattlt]

Since the panels are painted I see no continuity between panels, specially with wood frame. Har to say if any real advantage. Less dirt due to static?

Panels are overlapped with screws/nails driven through them. I think that would provide plenty of continuity.

How does this apply to lightning protection? If lightning strikes the building when the siding is bonded/grounded to the electrical system is there more of a risk of frying anything that's plugged in? More or less of a risk of burning the building down either way?

 

[theoldwizard1]

If it isn't intentionally grounded, you one day, may well wish it was. If that siding is floating (not connected) with respect to ground and becomes accidentally energized from any hot wire, it may kill you ...

This is the main reason why small electric appliances started to be grounded in the 50s. Most had exterior metal housings. A short from hot to the housing was a real possibility and a human could easily "complete the circuit" if the housing was not grounded.

Of course, "double insulation" and strong plastics, capable of being used for housings, have pretty much eliminated for this need. Funny how many electronic devices (laptop battery charges) still use 3 wire cords, even though they are in plastic housings.