Building Ground

Who's in charge of this project - you or 'they'?

Do you know why the existing building was grounded this way - what is the building used for?

Welded rebar structure, welded wire fabric reinforcement, reinforcing steel, and other miscellaneous connections should all be welded together providing electrical continuity.

Pro: Eliminates need for excessive and expensive copper, durable, long-lasting, essentially maintenance free.

Con: Also very expensive, time consuming, extra testing and inspection required.

See:IEEE-142/2007 ch.4.2.3 Concrete encased electrodes.

Our experience - in some of power station buildings-main building and auxiliary- it is as follows:

In all footing columns a single vertical steel rebar of minimum 1/2" diameter -depth underground of about 100 ft.[the most of power stations are located near sea shore and the soil is soft and the footing goes deep]is bounded to all the rebar by steel wire .At the top of footing this rebar is welded to the steel column foot screw .The connection between column is realized through the steel horizontal beam.

If there is a continue- all around- foundation it may be employed as horizontal link between footing groundings .The steel rebar for grounding segments have to be well welded-minimum 2" length of the welding.

The power station grounding grid is made of 4/0 stranded tined bare copper conductors. The connection to the foundation grounding through steel column by exothermic welding.

I would not recommend to use copper in concrete and not in connection with rebar.See[for instance]:

http://www.copper.org/applications/plumbing/techcorner/pdf/corrosion_nonferrous_metals_contact_concrete.pdf

Look up Ufer Earth on Google.

The method of grounding may be paramount to keeping the noise down.

Having to necessitate design modifications afterwards adds cost.

All of the different grounding methods available in the NEC (BS/IS) meet the safety ground requirements, however not all meet other requirements. That is why there are so many variants.

Yes... and because there are so many variants on how the grounding system may be implemented, he must first understand the current power system and how the new area will mesh with the existing power system. Once he has come to that understanding, he can then identify the best methodology to use to ground the new system extensions.

Implementing any grounding methodology without knowing if what is to be implemented is proper for the current and new systems is not appropriate if you ask me.

To my way of thinking... a design should always start at the beginning and work towards the desired end state and not from the end state back to the beginning. But... hey, that is just to my way of thinking.

We are very sensitive to noise on our grounding system.

When we constructed our building, that noise floor came first during the planning phase.

When we found that the existing power did not meet our restrictions, we landed a new feeder designed to match our needs.

If we had tried to patch our system around what was delivered it would have ended up in excessive costs in workarounds.

Any new construction must still meet the wickets required by our quiet ground. If it doesn't/won't, the idea is canned.

Hey there CP... I just noticed you were talking about your building and not that of the OP.

You make my point for me. You, and any designer, needs to know his base requirements and go from there, which is what you appeared to do. There was no indication of the OP having done that nor does there appear to be any effort towards that as he mentioned a full review is not likely to take place. A possibly error prone approach if you ask me.

I cannot speak to the OP's project. I can only provide procedures based on my requirements (past/ongoing experience) and those of the IEEE, NEC, etc.

Since we don't really know the base requirements of the OP's issue (and very rarely do, since we are not the consultants, engineers, or project managers) then the entire purpose of this forum appears to be moot.

One could always blow the dust off British Standard 7671, open it at page 1, and start reading.