250.104(B) Other Metal Piping 2014 NEC

[Dennis Alwon]

I also find this whole section odd in the sense that if there is a branch circuit feeding a gas appliance, then IMO it is not likely to be energized simply because there is an equipment grounding conductor. It seems like there is more likelihood that the gas line would become energized thru contact with copper pipes that may be energized thru a bad neutral downstream in a community where the water pipes are all copper underground. In this case even a bond wont help

 

[infinity]

IMO use of the word likely means that you don't need to do anything. Under normal conditions there is nothing that is likely to become energized.

 

[Dennis Alwon]

IMO use of the word likely means that you don't need to do anything. Under normal conditions there is nothing that is likely to become energized.

So if the equipment grounding conductor bonds it normally and we don't need any bonding otherwise why is it in the code?

 

[mwm1752]

So if the equipment grounding conductor bonds it normally and we don't need any bonding otherwise why is it in the code?

Covers all decades of wiring methods -- not all branch ciruits had EGC -- & now with the use of CSST the the EGC sizing has changed but not per NEC.

 

[infinity]

So if the equipment grounding conductor bonds it normally and we don't need any bonding otherwise why is it in the code?

I was commenting on the word likely. Likely means that it has a better chance of happening than not happening. There are metallic powered objects that are protected by an EGC just in case something happens that still doesn't mean that it is likely to happen.

 

[Dennis Alwon]

Covers all decades of wiring methods -- not all branch ciruits had EGC -- & now with the use of CSST the the EGC sizing has changed but not per NEC.

Csst is a different animal altogether. I guess you are correct. I wasn't thinking of old work but you would not need to bond the pipe if new work wasn't done . In other words if you install a new circuit then the gas pipe needs bonding with the equipment grounding conductor. Again it appears this article is basically ignored in the real world if you interpret it as written.

 

[RB1]

Years ago I went on a trouble call at a house where the entire plumbing system was energized. The water and gas lines were not bonded. I traced the problem back to a piece of NM cable that had been stretched tight across the corner of a floor furnace. Over many years the vibration caused by people walking over the floor resulted in the corner of the furnace cutting through the sheathing and caused the insulation on the conductor to fail. The ensuing ground fault was pulling about 17 amps when I measured it. In my view, NM cable in contact with metal piping that is not bonded is a hazardous situation.

 

[GoldDigger]

Most piping does not have sharp corners. Closest would exposed male threads outside a fitting.

 

[don_resqcapt19]

...IMO, proper premises wiring would never make any piping system "likely to be energized". Granted, such system may become energized through a fault... but that is a radically different concept.

Not according to CMP 5...they say "likely to become energized" means exactly the same as "may become energized".

I don't agree.

In general, I don't a gas line that supplies equipment that is also supplied with electric power as "likely to become energized"...sure it could happen, but is is very unlikely.

 

[Dennis Alwon]

In general, I don't a gas line that supplies equipment that is also supplied with electric power as "likely to become energized"...sure it could happen, but is is very unlikely.

That is exactly what I was saying in an earlier post. :thumbsup:

 

[Dennis Alwon]

Years ago I went on a trouble call at a house where the entire plumbing system was energized. The water and gas lines were not bonded. I traced the problem back to a piece of NM cable that had been stretched tight across the corner of a floor furnace. Over many years the vibration caused by people walking over the floor resulted in the corner of the furnace cutting through the sheathing and caused the insulation on the conductor to fail. The ensuing ground fault was pulling about 17 amps when I measured it. In my view, NM cable in contact with metal piping that is not bonded is a hazardous situation.

If there was an equipment grounding conductor then the circuit should open. Certainly a wire can get cut and energize duct work etc. I have never seen or heard of an authority having jurisdiction requiring the duct work to be bonded. I have seen duct work with flexible nonmetallic piping coming off the furnace.

 

[Smart $]

Not according to CMP 5...they say "likely to become energized" means exactly the same as "may become energized"...

Apparently they need a lesson in how to use a dictionary. English 101 wouldn't hurt either.

Either way, the notion is abstract. I may get struck by lightning. I may win the lottery. Likely to me means a substantially better than 50/50 chance of occurrence.

 

[Dennis Alwon]

Apparently they need a lesson in how to use a dictionary. English 101 wouldn't hurt either.

Either way, the notion is abstract. I may get struck by lightning. I may win the lottery. Likely to me means a substantially better than 50/50 chance of occurrence.

I agree with you Smart. I have talked to some of the CMP members and as I recall they were saying likely to be energized comes into play only if there is a circuit feeding the appliance. Well what is the equipment grounding conductor for then...?

 

[Smart $]

If there was an equipment grounding conductor then the circuit should open. Certainly a wire can get cut and energize duct work etc. I have never seen or heard of an authority having jurisdiction requiring the duct work to be bonded. I have seen duct work with flexible nonmetallic piping coming off the furnace.

250.4(A)...

(4) Bonding of Electrically Conductive Materials and
Other Equipment. Normally non?current-carrying electrically
conductive materials that are likely to become energized
shall be connected together and to the electrical supply
source in a manner that establishes an effective ground-
fault current path.

 

[Dennis Alwon]

250.4(A)...

I can just see some inspector making some poor guy bond all the metal grills in a non conductive duct system.

 

[Smart $]

I can just see some inspector making some poor guy bond all the metal grills in a non conductive duct system.

:rotflmaore: post)
:thumbsdown: (re: inspector)
:weeping: (re: poor guy)

 

[charlie b]

FWIW, "likely to happen today" is vastly different from "likely to happen once during the 40 year expected life of the equipment." We design for the later case.

 

[don_resqcapt19]

Apparently they need a lesson in how to use a dictionary. English 101 wouldn't hurt either.

Either way, the notion is abstract. I may get struck by lightning. I may win the lottery. Likely to me means a substantially better than 50/50 chance of occurrence.

I agree, but if you go back and read the panel statements from when the wording was changed from "may become energized" to "likely to become energized" you will see that panel 5 said they mean the same thing.

 

[Smart $]

I agree, but if you go back and read the panel statements from when the wording was changed from "may become energized" to "likely to become energized" you will see that panel 5 said they mean the same thing.

If it means the same thing, then why did they change it... :?

With as abstract as either is, it doesn't make them any less wrong IMO.

I'd rather see the requirement written in a concrete, definitive manner.

 

[GoldDigger]

I'd rather see the requirement written in a concrete, definitive manner.

Such as "whose probability of becoming energized during any one year period is greater than .10"?
And requiring a PE for every such calculation?