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#96247 - 11/13/05 09:44 PM Black Pipe bonding  
ahultin  Offline
Junior Member
Joined: Nov 2005
Posts: 4
Bonsall, Ca USA
I am building a new home in North San Diego County. I have yet to get an answer from the AHJ and my electrician does no know the answer so I figured Id post it here. I have black pipe installed in my garage for compressed air. This will be isolated from the compressor by a 2 ft section of hydraulic hose. I am aware of the requirement to bond the gas service however do not know if this will be required to be bonded also. If so, would it be acceptable to attach it to the ufer as the knockouts to the main panel (siemens 400amp combo) are full.
Thank You


2017 / 2014 NEC & Related Books and Study Guides

#96248 - 11/14/05 01:07 AM Re: Black Pipe bonding  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
We usually don't answer home-owner questions, but...

Quote
250.104(B) Other Metal Piping. Where installed in or attached to a building or structure, metal piping system(s), including gas piping, that may become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as the bonding means. The points of attachment of the bonding jumper(s) shall be accessible.


Could it become energized? If not, not required. Maybe? Either way that would be up to inspector to decide. If you want it bonded, thats another story... And yes, to the ufer with a split-bolt in an accessible location would be OK, from a clamp in an accessible location on the pipe. IMO If this is for say a home shop, or something, I would.... But have your electrician do it...


Mark Heller
"Well - I oughta....." -Jackie Gleason

#96249 - 11/14/05 01:33 AM Re: Black Pipe bonding  
ahultin  Offline
Junior Member
Joined: Nov 2005
Posts: 4
Bonsall, Ca USA
Thank You.
I am the acting as the GC on this project and have learned much from this site and do appreciate it. It was quite interesting to see the response from the different ec's bidding the job to the questions I was able to pose in the job specs, much grabbed from the violation forum.For instance, the Ec I went with was one of only two that would agree to not backstabing. The EC will definately do it, he just had never seen the compressed air lines done in other than pvc if done at all he is strictly residential.


#96250 - 11/14/05 06:18 AM Re: Black Pipe bonding  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
e57 already gave you some good advice so this is just a side note. [Linked Image]

Quote
This will be isolated from the compressor by a 2 ft section of hydraulic hose


I doubt highly this will electrically isolate the line from the compressor.

If it is truly hydraulic line it will carry significant current.

Hydraulic lines have steel braid inside to contain the high pressures involved.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#96251 - 11/14/05 08:20 AM Re: Black Pipe bonding  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
Totally off topic, but :
Quote
The EC will definately do it, he just had never seen the compressed air lines done in other than pvc if done at all he is strictly residential.


My understanding is that PVC pipe is _not_ recommended for compressed gas service. OSHA document here http://www.osha.gov/dts/hib/hib_data/hib19880520.html

Please remember that a pipe filled with compressed gas at a given pressure stores far more energy than a pipe filled with liquid at the same pressure. In the event of a pipe failure that energy goes into physically moving pieces of the pipe around.

-Jon


#96252 - 11/14/05 11:18 AM Re: Black Pipe bonding  
ahultin  Offline
Junior Member
Joined: Nov 2005
Posts: 4
Bonsall, Ca USA
Thank you, that is why mine was plumbed in black pipe vs pvc.


#96253 - 11/15/05 04:29 AM Re: Black Pipe bonding  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Quote
If it is truly hydraulic line it will carry significant current.

Hydraulic lines have steel braid inside to contain the high pressures involved.


Bob, true... But will the carry that fault current safely? Even if they have steel braiding, they must have sufficiant contact with the fittings. If they were to take a hit from any circuit, the fitting and braid contact if any, would be the weakest link, and under considerable pressure.

However I was thinking more along the lines of equal potential in a shop setting. If not from the compressor itself, which have a tendancy to shake all of thier parts loose, maybe another circuit. Just using my imagination here: If this shop is (Even in a home) big enough to have piped compressed air, then its big enough for other large equipment, like a welder... Who knows? Oh ahultin does.... Whats the shop for big guy?

Anyway, the hose could be removed, abandoned, whatever and you would still have a large metal conductor running around carrying voltage.

Now watch this... This is where we debate the nature of the code....
"The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s)."
It says circuit that may energized the pipe, that doesnt nessesarily mean the compressor. If you have a 1/2" or larger pipe running around the room, that could mean any equipment in the room. That compressed air could be connected to another, or multiple machines of higher amperage.

I recently worked on a cabinet shop that had several machines like automated mortice machines, that had pnmematic automation and sizable 3 phase 480 motors. Oh wait, my friendly glass guy has a 200A behemoth of a glass shaper that eats 2" X 12'X whatever size glass, that also uses air from a 30A compressor that feeds the rest of the shop. (There the air is bonded to structural steel by common framing.) True they all have EGC's but would the hose that feeds them qualify as a bond?


Mark Heller
"Well - I oughta....." -Jackie Gleason

#96254 - 11/15/05 05:39 AM Re: Black Pipe bonding  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Quote
It says circuit that may energized the pipe, that doesnt nessesarily mean the compressor.


IMO that is exactly what it means. [Linked Image]

You left out the 'rest of the story'. [Linked Image]

Part of 250.104(B)
Quote
The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as the bonding means.


If it does not mean that this compressor circuit how do you size the bonding jumper?

Do you size the bonding jumper based on the largest circuit in the room or the largest circuit in the building?

All this is not to say I am against bonding the line my point is only that you do not have to if you chose not to.

I am at a loss to understand what may energize this line if not the compressor?

All other electric equipment in the shop is alread required to be bonded.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#96255 - 11/15/05 05:42 AM Re: Black Pipe bonding  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
By the way read my first post.

My only point there was not to count on the Hyd. line to isolate the black pipe. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#96256 - 11/15/05 02:07 PM Re: Black Pipe bonding  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,104
Estero,Fl,usa
Bob I always looked at that "likely to energize" as any equipment located close to the pipe in question. If the compressor was a 1hp, served by a 14ga circuit you could bond to the 14ga EGC but what happens if there is also a 15 KW electric heater next to that pipe a little farther along?
The safest answer might be 250.66 but I agree that is usually overkill.


Greg Fretwell

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