Multi-Point Grounding System

[strippers&dykes]

Hey all,

So I'm wondering if anyone can help me understand what multi-point grounding is? This shelter is small, 12ftx20ft and they are saying it needs a multi-point system, but there specs are configured for large buildings.

I work with Telecommunication shelters that are precast concrete. I work with customers such as Tmobile, Verizon, FAA and anyone who deals with radio frequency which require a lot of grounding. I am familiar with R-56 and Harris grounding standards but I'm not fully sure i understand what multi-point is.

Any info on this would be great.

May the Fourth be with you!

 

[ron]

It generally means that each peice of equipment has multiple interconnections to the grounding system, like a ground grid.

Multiple paths for interconnection.

 

[cuba_pete]

not trying to be mean...really

not trying to be mean...really

I am honestly not trying to be mean here...

If you work in the telecomm industry, how do you not know what a multipoint ground is?

Do you only deal with cellular customers? (if you do, then I guess that would make some sense). The precast structures would likely be bonded throughout, hence, a multipoint ground.

Is the shelter ground provided when delivered, or do you have to make it?

Please pardon my rudeness...I have dealt with multipoint grounds for my entire career.

 

[iceworm]

...
Please pardon my rudeness...I have dealt with multipoint grounds for my entire career.

So having dealt with "multipoint grounds" for an entire career makes it okay to be rude? Retorical question - it doesn't.

So, instead, enlighten us. The only multipoint grounding I am familiar with is 250.180.C - which has nothing to do with Comm.

So, tell us. As relates to Comm, what exactly is "multipoint grounding"?

ice

 

[cuba_pete]

well then...

well then...

I wasn't being rude. It is really difficult to type an honest question and have it come across as intended when it is totally up to the person reading the words to add inflection, tendency and meaning to them.

A multipoint ground is also referred to as a equipotential ground (equipotential plane), signal reference grounding grid, signal reference grounding plane, etc. The system can be calculated as a spatial capacitor and should also be designed for the frequency(ies) of interest.

For the layman: refer to IEEE Std 1100-1999 Emerald (color series, which I still use), IEEE Std 142-1991 Green.

I also have several MILSPEC instructions, guidance, and handbooks (Red/Black communications, TEMPEST, etc.) in which multipoint grounds are common fare.

I find it surprising that a radio technician who is responsible for ensuring the proper installation and testing of a radio transmission facility would even ask what a multipoint ground is.

If you have to ask for a definition of standing waves or the purpose reducing noise to improve transmission loss...:weeping:

 

[strippers&dykes]

I'm glad that someone with so much experience with these systems is of such great help. With responses like that its easy to find the trolls here.

I'm new to this industry and haven't had to deal with such redundant grounding before, I am about 4 months in and learning as I go. Harris and R-56 grounding I have become proficient at and this customer has their own specs different from both. The reason I ask for clarification of a multi-point is that these shelters are so small and don't have much to make multi-points to.

Also I'm not a radio technician, I'm a field electrician transitioning into a project manager position. Projects I've worked prior to this I haven't had to deal with this kind of extensive grounding.

So thanks for the super informative post :thumbsdown:. With that kind of experience you could of actually provided some good feedback but instead just wanted to troll:slaphead:.

Happy Cinco de Mayo!

 

[Smart $]

.... Harris and R-56 grounding I have become proficient at and this customer has their own specs different from both. The reason I ask for clarification of a multi-point is that these shelters are so small and don't have much to make multi-points to.

...

Not familiar with telecom multipoint grounding or the Harris and R-56 grounding you refer to, but if the specs differ enough for you to question their implementation, you should RFI the appropriate party.

Multipoint grounding is a method which results in two or more grounding paths to each equipment unit. It is commonly referred to as a loose grid. Seldom does the implementation physically resemble a grid, but it "very loosely" resembles a grid when drawn as a schematic representation.

FWIW, the grounding method required by the NEC uses a star topolgy. However, in buildings having a metal framework and other building elements, multiple grounding paths are created inadvertently. With multipoint grounding, the paths are created intentionally and with purpose outside (or beyond if you prefer) the safety considerations which drive NEC requirements.

 

[Smart $]

...

For the layman: refer to IEEE Std 1100-1999 Emerald (color series, which I still use), IEEE Std 142-1991 Green.

I also have several MILSPEC instructions, guidance, and handbooks (Red/Black communications, TEMPEST, etc.) in which multipoint grounds are common fare.

...

References, yes... but not intended for the layman.

 

[strippers&dykes]

I have done the RFI, but even the customer themselves cant provide a clear answer as their specs were not written pertaining to a small shelter that is 192sq ft. They were written as a general scope for built in place with multiple utilities and such. They have just started dealing with these small precast shelters. :slaphead:

 

[Smart $]

I have done the RFI, but even the customer themselves cant provide a clear answer as their specs were not written pertaining to a small shelter that is 192sq ft. They were written as a general scope for built in place with multiple utilities and such. They have just started dealing with these small precast shelters. :slaphead:

Sounds like someone didn't do their due diligence... and passing the buck on to you. :happyyes:

 

[strippers&dykes]

Sounds like someone didn't do their due diligence... and passing the buck on to you. :happyyes:

Yeah that's exactly what happened in this situation. I think I have a pretty good idea of what needs to be done. I drew a CAD model of how our layout would work and sent it over to their engineer. I'll hear something today.

 

[cuba_pete]

Wiki wiki wiki...it's a (w)rap...get it?

Wiki wiki wiki...it's a (w)rap...get it?

References, yes... but not intended for the layman.

Then I guess Wikipedia would be the layman's reference

When I typed "multipoint ground" into Google, the Wikipedia page for multipoint ground was the first hit.

I guess "layman" wasn't the proper term to use...that would be a person who is not qualified in a given profession and/or does not have specific knowledge of a certain subject. Since the OP is actually contracted/paid to perform work which should only be attempted/completed by a qualified person...wait...what?

Damn, I cannot make this sound like I am not trying to be a smartass no matter how I try to make it sound okay that the OP doesn't understand the specs for a job which he/she is being paid to do...and tattling on the customer (who must assume that a qualified person, and not a layman is doing the work).

Damn, did it again...

Honestly, the IEEE references I provided are much clearer than even the NEC...

 

[don_resqcapt19]

As long as the specs do not call for something that is prohibited by the NEC, you can do that grounding any way that they want you to. There are a number of variations on what different designers call for for installations like this.

The two big things that the NEC says you can't do is have multiple points of connection between the grounded conductor and the grounding conductors, and you can't have a grounding system that is totally isolated from the electrical grounding system.

 

[Smart $]

...

I guess "layman" wasn't the proper term to use...that would be a person who is not qualified in a given profession and/or does not have specific knowledge of a certain subject. Since the OP is actually contracted/paid to perform work which should only be attempted/completed by a qualified person...wait...what?

...

Don't confuse the issues. OP is contracted to perform the work, and as exhibited, is not the professional paid to design (having to comply with uncommon second or third party spec's). Place the blame squarely where it is due.

(And on the smartass thing, I can usually one up anyone, anytime I choose... but my years of experience and acquired wisdom steer me towards the least-ostentatious choice )

 

[captainwireman]

There must be a way to contact the manufacturer of the skid/building. I would think they would have more relevant information as opposed to the customer.

 

[cuba_pete]

If...

If...

If the "OP is...not the professional paid to design" then why is he/she submitting a CAD drawing to the engineer? ("I drew a CAD model of how our layout would work and sent it over to their engineer")

It looks like that's exactly what they did/are doing. If they are only the pro doing the work, then the design should be first with implementation by them.

I still find it quite hard to believe that since they just learned (apparently starting on this forum) what a multipoint ground even was, and just days later they submit a CAD drawing...that's just crazy.

I can see where so many electricians get the idea that multipoint and single point grounds are pointless when the engineering looks so sloppy.

One-upmanship for sloppy unqualified work? You can have it, you win.:thumbsup:

 

[Smart $]

If the "OP is...not the professional paid to design" then why is he/she submitting a CAD drawing to the engineer? ("I drew a CAD model of how our layout would work and sent it over to their engineer")

It looks like that's exactly what they did/are doing. If they are only the pro doing the work, then the design should be first with implementation by them.

Let's be clear. If the EC entered an installation agreement only, and not a design-build agreement, he is not getting paid to design. With an EOR this appears to be the case. If the installation documentation is not comprehensive, clear, concise, and complete, the fault lies clearly on the EOR... period. Too often nowadays EOR's want paid top dollar for their work yet issue boilerplate specifications and then hide behind a disclaimer regarding errors and omissions, perhaps even include a clause placing the responsibility for such on the contractor.

Touchy subject matter, so I'm going to stop there...

I still find it quite hard to believe that since they just learned (apparently starting on this forum) what a multipoint ground even was, and just days later they submit a CAD drawing...that's just crazy.

What's crazy is your condescending attitude. The OP's situation should not even exist, yet you're berating him for wanting to clarify the matter!!!

I can see where so many electricians get the idea that multipoint and single point grounds are pointless when the engineering looks so sloppy.

Finally... a sensible comment.

 

[cuba_pete]

I get that a lot...

I get that a lot...

I get the condescending attitude thing a lot from people.

I especially get it when electricians show up to work and don't understand what they are supposed to be doing, whether it is their fault or not (mis-hired?).

I have 27 years in the government dealing with installation of complex electrical and electronic systems. It takes us forever and a day to even get the project to the start date. When workers show up and don't understand what's required it slows the process to a crawl.

This, believe it or not, is a huge part of the problem...it's roughly 70% getting it to start, then 30% implementation (in my experiences). This is also why we try to keep the same contractors doing work for us "sole source".

Back on-topic...this is still part of getting to Jman status. Seems like the OP should at least displayed some comprehension of grounding methods for the telecomm industry.

But, also in all fairness, the multipoint ground is not directly related to electrical work (safety ground) as much as it is electronic (performance of the comm gear).

I am fairly confident that after 5-10 jobs like this the OP will be a sage who could answer questions about these types of installations...even on the Mike Holt forum.:angel:

 

[don_resqcapt19]

...
I especially get it when electricians show up to work and don't understand what they are supposed to be doing, whether it is their fault or not (mis-hired?).
...

I would expect in many cases, that is a direct reflection on the quality of the construction documents and not on the quality of the worker.

 

[Smart $]

...
I especially get it when electricians show up to work and don't understand what they are supposed to be doing, whether it is their fault or not (mis-hired?).

I have 27 years in the government dealing with installation of complex electrical and electronic systems. ...

... This is also why we try to keep the same contractors doing work for us "sole source".
...
But, also in all fairness, the multipoint ground is not directly related to electrical work (safety ground) as much as it is electronic (performance of the comm gear).
...

If you know this, why not impart some of your knowledge, rather than put others down for not knowing.

...
Back on-topic...this is still part of getting to Jman status. Seems like the OP should at least displayed some comprehension of grounding methods for the telecomm industry.
...
I am fairly confident that after 5-10 jobs like this the OP will be a sage who could answer questions about these types of installations...even on the Mike Holt forum.:angel:

It is not part of getting JW status. It is a sub-industry thing. I'm certain you did not know anything about multipoint grounding at some point in your career. Other people are the same, and it is not directly related to their age, company position, or J-man status.