Sprinkler Piping for Grounding Electrode

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DSTP

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The question pertains to the grounding electrode of the separately derived system, 250.30. It is a typical distribution system with the main service entrance in the basement with 480V, 4W feeders distributing power to remote electric rooms (11). Within each electric room there is a dry type transformer used to step down to 120/208V. The electrical rooms are located on upper levels. The challenge is that the building is very old and has no steel structural skeleton. There are steel bar joists in individual rooms spanning between masonry. The facility does have a full time maintenance staff.
The only apparent grounding electrode is the sprinkler piping running through each electric room, 250.30(A)(7)(1). The piping is black iron with threaded joints without any flanges, pumps, etc except at the main electrical room where jumpers will be installed. All available grounding electrodes within the main electric room will be bonded together. I understand that 250.52(A)(1) requires this to be within 5ft from the point of entrance, with an exception that ensures only qualified persons service the installation (which is the case).
250.104(D)(1) requires the sprinkle piping to be bonded in the area served (the electrical rooms) and Exception No. 1 excludes this requirement if the water piping system is used as the grounding electrode system.

So I guess my real question is: since the sprinkler piping is the only grounding electrode available in these remote electric rooms, is it permissible to use them? Using a grounding electrode conductor from each transformer to the piping? Installing bonding jumpers where required?
 
DSTP said:
So I guess my real question is: since the sprinkler piping is the only grounding electrode available in these remote electric rooms, is it permissible to use them? Using a grounding electrode conductor from each transformer to the piping? Installing bonding jumpers where required?
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It is my understanding that the sprinkler pipes are not allowed to be used as a grounding electrode. This is not an NEC rule but , I believe, a fire code ruling.
 
The Sprinkler pipes are not listed as one of the electrodes recognized in 250.52 permitted for grounding.
250.104 requires them to be BONDED, adding to safety in the event they should be energized.
 
250.52 lists the electrodes that can be used for grounding. 250.104 requires that the sprinkler system be BONDED to the electrode system, but cannot be the electrode.

opps! it posted twice!
 
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There is a similar problem with using the gas pipe as an electrode. The NEC may require you to use all available electrodes but the gas company, at least around here, will have a fit if you hook to there pipe. They generally use a dielectric fitting to insure that you do not use their pipe as an electrode.
 
Gary Hill said:
The Sprinkler pipes are not listed as one of the electrodes recognized in 250.52 permitted for grounding.
250.104 requires them to be BONDED, adding to safety in the event they should be energized.
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Yes they are actually bonded thru the EGC that goes to the fire pumps. I bet the sprinkler pipes have a dielectric fitting also.

BTW, welcome to the forum- both you and the OP.
 
In NFPA 24 Standard for Installation of Private Fire Service Mains and their Appurtenances articles 10.6.8 and 10.6.8.1. Look in index A at the notes for these two sections and it will explain that the underground pipes cannot be used as an electrode but they should be "bonded and grounded" as per NFPA 70.
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Sprinkler Pipe as Grounding Electrode

Sprinkler Pipe as Grounding Electrode

Where in the NEC code is using a sprinkler line specifically prohibited as a grounding electrode - there is no definiation of metal water piping or differentiation between types of allowed metal water piping, Section 250.22 A 1 Exception allows connection to metal water piping as a grounding electrode > 5lf from point of entrance where conditions of maintance and supervision exists by qualified individuals?

Thanks
 
DSTP said:
Where in the NEC code is using a sprinkler line specifically prohibited as a grounding electrode - there is no definiation of metal water piping or differentiation between types of allowed metal water piping, Section 250.22 A 1 Exception allows connection to metal water piping as a grounding electrode > 5lf from point of entrance where conditions of maintance and supervision exists by qualified individuals?

Thanks
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Ya good luck with that logic.
If you have ever paid close attention to the parts used to assemble fire sprinkler systems (black pipe) the "Red" fittings that are used to connect the black pipe have a large rubber "O" ring on them, they are not threaded fittings. The black pipe has a groove pressed into it and the "O" ring fits between it and the red fitting. This effectively cuts off the ability to be a "low impedance" ground path.
 
Dennis Alwon said:
In the second post I stated that this is not an NEC rule but a fire code rule. I am not sure where that is.
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A good point, we are not only under the NEC, but also any code or material referenced by the code that applies to an installation.
 
DSTP said:
Where in the NEC code is using a sprinkler line specifically prohibited as a grounding electrode - there is no definiation of metal water piping or differentiation between types of allowed metal water piping, Section 250.22 A 1 Exception allows connection to metal water piping as a grounding electrode > 5lf from point of entrance where conditions of maintance and supervision exists by qualified individuals?

Thanks
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You will have to bond the sprinkler system regardless, and there will be no difference in how that has to be accomplished. But the ultimate decision on whether this satisfies the grounding electrode requirements is going to be made by your local building and fire officials. Suggest you contact them and get a definitive answer.
 
Smart $ said:
You will have to bond the sprinkler system regardless, and there will be no difference in how that has to be accomplished. But the ultimate decision on whether this satisfies the grounding electrode requirements is going to be made by your local building and fire officials. Suggest you contact them and get a definitive answer.
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Yes but the op states this must be done withing 5' of where the sprinkler pipe enters the building. If the fire regs state don't use it as an electrode then you need to be on the load side of the dielectric fitting- if there is one.
 
Dennis Alwon said:
Yes but the op states this must be done withing 5' of where the sprinkler pipe enters the building. If the fire regs state don't use it as an electrode then you need to be on the load side of the dielectric fitting- if there is one.
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The OP mentions the <5' rule, but then refers to the exception... where connection can be anywhere on the system.

If fire regs say it can't be used as an electrode, then it can't be used as an electrode regardless of the point of connection, and a bonding jumper around a dielectric fitting would also likely be prohibited.

However, if (and I do not know the probability) there is no dielectric fitting, I don't see why a threaded sprinkler system cannot be used as an electrode (provided it is also used as an electrode for the service) since it is required otherwise to be bonded with a jumper equivalent to a GEC. Once bonded, it will act as an electrode regardless of whether it is called one or not, as the electrical charges imposed do not stop, check ID, and turn away if not called an electrode under the NEC. :D
 
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