ECN Forum Forums Code Related Discussion NEC & other Code issues Structural Steel

I am confused as to how this can be so confusing. It is clearly stated in plain english "....interconnected to form a steel building frame" How the heck can some one say a single steel beam under a house is anything close to that? To me there is not even interpretation needed as this is clear as can be. The '05 changes the wording somewhat to make it even clearer. It uses the word "metal" building frame. No big deal there. BUT it changes "May become energized" to "LIKELY to become energized". In my view if the steel is "likely" to become energized somebody screwed up bigtime.

It does say that.

Now you are spinning. "Interconnected to form a steel building frame" Where do you see the word "Structure"? You added that. A couple of pieces of steel for support do not "Form a steel building frame" .

Another point on Bob's "inspector" comment. I tend to agree with what he said. I too would fight this if an inspector told me I would have to bond a beam in this situation. As I wrote in another topic there are those that believe that the NEC says you have to bond any and all metal period. It does not. As I stated I was at a grounding and bonding class where the "Instructor" (term used lightly) pointed out that single steel support beams, lally columns, oil tanks, one foot sections of copper pipe stubbed out to bathroom fixtures from plastic pipping systems etc must be bonded. Pretty obvious as to why there is so much confusion. People tend to take everything they hear as gospel. I don't.

Sorry about the swimming pool FUD, I was just referring to what can result from bonding paranoia.
I still like the concept of bonding metal to the EGC of the circuit likely to energize the metal in question. If your 1 foot of isolated metal pipe serves an instant water heater I would want to be sure the EGC of the heater was effectively bonded to the pipe.

Different bonding requirements but I would say we are not required to bond that either.

1' of copper pipe does not constitute a metal piping 'system'.

This is much like the above argument about the steel building frame.



I can see no way we can call a isolated 1' piece of copper tubbing a 'system'.

By the way if you do apply the bonding to this isolated piece of pipe the conductor would need to be sized per table 250.66 not 250.122 so the EGC of the heater is not acceptable.

This IMO makes the thought of bonding small pieces of pipe even more ridiculous.

Bob

This thread has entered the Bizarro world. This I'd love to see. What about the metal towel bar under the sink that sits right next to this instant hot water dispenser or the spout that sticks out of the counter to dispense the hot water. Imagine all the runs of #4 cu running all over the house.

[This message has been edited by Electricmanscott (edited 02-14-2005).]

If that towel bar was heated it should be bonded, as they are, via the EGC of the circuit likely to energize it (the 3d prong on the plug). The same should be true of any plumbing going to an "insta'hot".
I certainly agree with those who say you don't need to bond every scrap of isolated pipe or other metal. Only those likely to be energized by attached equipment.
If we get back to the beam, I would only be oncerned if it had equipment hanging from it and I would want it bonded to that equipment's EGC. Incidental contact with cables running nearby should be handled with the securing and physical damage articles.

Same problem as the instahot, if we try to apply the bonding requirements of 250.104 the EGC is not enough.

Both those sections require a 250.66 sized bonding conductor.

As Scott mentions that will be 4 AWG copper for a house with a 200 amp service.

The equipment mounted to the beam or the instahot connected to that 1' piece of copper tubing cannot energize either if they are installed per code with proper EGCs.

I would tend to believe what the CMP-5 was refering to was a single steel beam with support posts of wood...which is often installed in a single family dwelling.

If George Little's steel I beam supported by a steel post set on concrete in contact with the earth were to be exposed to a ground fault and it wasn't bonded according to 250.104(C)...there would not be a low-impedance path to carry the ground fault current, which would not allow the over current device to open.This steel beam would be live.

In a industrial or commercial enviroment, this steel may not be likely to become energized, for hopefully only qualified personal would be installing wiring apparatus nearby.

But in the residential world it may be likely to become energized by some of the wiring I have seen by DIY homeowners.I just had to clean up a basement with extension cords running everywhere and the guy had adaptors in his keyless with 2-wire lamp cords strung all over the place, wrapped around gas piping and strung over metal duct work.

I still believe after all that has been debated here that George Little's (exposed) steel would have to be evaluated by the AHJ to see if it were to present a hazard.

As for the wording change to 250.104(C) from "steel" to "metal"...I think that this wording change adds a whole new list of bonding requirements.

Metal: any of class of elementry substances that are good conductors of electricity.

Steel: a hard,tough alloy of iron with carbon.

You see, the word METAL does't just limit bonding to steel.

Structure...the first sentence of 250.104(C) mentions exposed STRUCTURAL steel. (2002 NEC)

As far as some of the other equipment mentioned here such as the instant hot water or the heated towel bar...those pieces of equipment must be grounded(not bonded) according to 250.134 or 250.138

shortcircuit

I haven't seen a wood support post installed in the past 25 years.
Don