Grounding electrode system for a new 3 story office building

[ksmith846]

A little help here please.......awarded a job recently and after we signed the contract the owner and GC asked us to offer any savings ideas we could.

One idea was to reduce the overkilled Grounding Electrode System as designed by the engineer. Their design was to install 30 feet of ground rod in a 30'x30'x30' triangular configuration with #4/0 bare copper to run between all 3 grounding electrodes to the footing steel and back to the service disconnect. Also to provide testing results to prove we met 5 ohms of resistance.

Considering the minumum code is to plant two ground rods with a maximum of #3/0 copper and tie to all available electrodes why are they requesting this installation. We have been taught via Mike's classes that Ground rods and GE systems are just to bleed off induced voltage from nearby lighting strikes....??

This is what the Engineering firm wrote to the GC and owner once they were asked to change the drawings to save the owner $$

"Our electrical design was intended to go above the minimal code requirements of 25 ohms, and was designed for the electrical system to be completely and effectively grounded with the grounding system not to exceed 5 ohms. We will not accept this VE change unless the owner provides a letter requesting the EOR's acceptance of this design change, and releases FAE from any potential issues resulting from electrical system not being effectively grounded."

Isn't my GE system completely and effectively grounded without having to reach 5 ohms with a huge triangular system?

 

[bphgravity]

I see this same thing all the time. I cannot explain to you why electrical design professionals continue to specify grounding electrode systems way above-and-beyond the NEC minimum requirements. Lack of continuing education, training, experience, maybe all three???

Meeting just the NEC requirements for the grounding electrode system would by definition (and by natural physics) be "effectively grounded". The grounding detail you describe would likely NOT make the system any safer, more effective, or more efficient. It would however, be more expensive, more labor intensive, and require more material resources without a truly definable benefit...

 

[ksmith846]

Thanks for your input........that's what I have been telling the GC and owner all along.....they asked for cost saving options and I provided them a few....one of which being to reduce the GE system.

 

[roger]

I see this same thing all the time. I cannot explain to you why electrical design professionals continue to specify grounding electrode systems way above-and-beyond the NEC minimum requirements. Lack of continuing education, training, experience, maybe all three???

I think all three and throw in Lack of understanding what a GES does at low voltages. I still hear designers tell owners that they are providing this overkill so they will not have problems with elctronic equipment.

Meeting just the NEC requirements for the grounding electrode system would by definition (and by natural physics) be "effectively grounded". The grounding detail you describe would likely NOT make the system any safer, more effective, or more efficient. It would however, be more expensive, more labor intensive, and require more material resources without a truly definable benefit...

Amen

Roger

 

[jumper]

First, I want to know if these are stamped and approved( CBO or plans review) drawings/calculations by an EE.

If so, design issues aside, it is his liability and O and E insurance here. You do not just get to follow the parts of a plan you agree with. If you want to change something and and the EE/PE says no, it is his right to pull his stamp and walk away.

Right, wrong, or indifferent-you follow the plans.

 

[cdslotz]

Usually a grounding system as you described are tied to a grounding counterpoise system around the perimeter of the building, then to a ground riser with copper bus bars to all electrical rooms, tele/data rooms, and then to the Lightning Protection system. So basically that is 4 systems, 1) electrode 2) counterpoise 3) ground riser 4) LPS.
Most new buildings have a ton of computer, audio/visual requirements.
Yes the grounding designs are overkill, but the EE's liability are at stake, so if the owner wants to value engineer any of that system down, the EE is off the hook. That's why he is requiring a letter.

Question: Are there any of the other grounding systems on this building as I described? The electrode is the least expensive of all of these.
I don't see that much savings in a code minimum electrode system.

 

[petersonra]

Considering the minumum code is to plant two ground rods with a maximum of #3/0 copper and tie to all available electrodes why are they requesting this installation.

Code does not require any ground rods at all.

 

[jumper]

Yes the grounding designs are overkill, but the EE's liability are at stake, so if the owner wants to value engineer any of that system down, the EE is off the hook. That's why he is requiring a letter.

Yep, yep, and yep. but OTOH if he/she specs it, I install it exactly like drawn, and there is a problem- the EE gets to take the fall, not me.

 

[bphgravity]

Here is a perfect example of a plan I am currently reviewing for a large metal building on a concrete slab:

Ground Ring. Install a grounding conductor, electrically connected to each building structure ground rod and to each steel column, extending around the perimeter of the building area or item indicated.

1. Install tinned-copper conductor not less than No. 2/0 AWG for ground ring and for taps to building steel.
2. Bury ground ring not less than 24 inches from building foundation.

Ufer Ground (Concrete-Encased Grounding Electrode). Fabricate according to NFPA 70, usinf a minimum of 20 feet of bare copper conductor not smaller than No, 2/0 AWG.

1. if concrete foundation is less than 20 feet long, coil excessive conductor within base of foundation.
2. Bond grounding conductor to reinforcing steel in at least four locations and to anchor bolts. Extend grounding conductor below grade and connect to building grounding grid or to grounding electrode extrernal to concrete.

Report measured ground resistances that exceeds the following values:

Power Distribution and Panelboard Equipment - 3-ohm(s).

This is a 39,500 square foot building. There are 24 exterior columns. By the way, this is not for lightning protection. This is the detail for the elctrical service grounding only...

 

[roger]

First, I want to know if these are stamped and approved( CBO or plans review) drawings/calculations by an EE.

If so, design issues aside, it is his liability and O and E insurance here. You do not just get to follow the parts of a plan you agree with. If you want to change something and and the EE/PE says no, it is his right to pull his stamp and walk away.

Right, wrong, or indifferent-you follow the plans.

Derek, when an owner or GC ask for VE suggestions it is normal for the subs to bring to attention items that can be deleted for savings and this is one I would bring up with out hesitation. If the engineer of record doesn't like it he/she can take it up with their customer and a savy customer should ask for back up to the reason for the designers objections.

When it is said and done a code compliant installation should not offend a designer and they shouldn't have a big issue with standing behind their seal.

Roger

 

[roger]

Bryan, that sounds like a telephone company specification.

Roger

 

[jumper]

Derek, when an owner or GC ask for VE suggestions it is normal for the subs to bring to attention items that can be deleted for savings and this is one I would bring up with out hesitation. If the engineer of record doesn't like it he/she can take it up with their customer and a savy customer should ask for back up to the reason for the designers objections.

When it is said and done a code compliant installation should not offend a designer and they shouldn't have a big issue with standing behind their seal.

Roger

Hmm, common sense, I gotta think about that one.

 

[ksmith846]

First, I want to know if these are stamped and approved( CBO or plans review) drawings/calculations by an EE.

If so, design issues aside, it is his liability and O and E insurance here. You do not just get to follow the parts of a plan you agree with. If you want to change something and and the EE/PE says no, it is his right to pull his stamp and walk away.

Right, wrong, or indifferent-you follow the plans.

Of course the plans are stamped and approved....the owner requested all trades to offer VE options. We did and this was one of them.....they accepted so I told them to get the EOR's approval. That is why we are this hurdle now.

If the EOR convinces the owner to keep the GES as drawn I will install it per plans as I had already bid it per plans.

I am taking exception to the EOR inferring that by converting to a typical GES that the system will not be effectively grounded unless it's done their way. That is just not true. So by their wording they make me seem to the owner that I do not know what I am doing.

 

[ksmith846]

Usually a grounding system as you described are tied to a grounding counterpoise system around the perimeter of the building, then to a ground riser with copper bus bars to all electrical rooms, tele/data rooms, and then to the Lightning Protection system. So basically that is 4 systems, 1) electrode 2) counterpoise 3) ground riser 4) LPS.
Most new buildings have a ton of computer, audio/visual requirements.
Yes the grounding designs are overkill, but the EE's liability are at stake, so if the owner wants to value engineer any of that system down, the EE is off the hook. That's why he is requiring a letter.

Question: Are there any of the other grounding systems on this building as I described? The electrode is the least expensive of all of these.
I don't see that much savings in a code minimum electrode system.

This is new 3 story Law Office Building. They did not design with a ground ring.....they did not design with lighting protection....they did not even design with surge protection......instead they design a GES with 3 sets of 30 feet of ground rod (FYI this is right next to the intercoastal waterway and we are only 9 feet above sea level).

I have been trained that the GES is soley to bleed off induced voltage from nearby lighting strikes. Which really only requires a minimum system to acheive this goal. An overkilled 5 ohm system will not in my opinion do a better job. What the EOR should have spent the owner's money on was surge protection at the service. That will protect the sensitive equipment much better than a wasted 5 ohm GES.

 

[ksmith846]

I don't see that much savings in a code minimum electrode system.

Let me address the cost savings.....how can you say it's not a cost saver?

My system......(2) 10' x 5/8" copper clad ground rods...6 feet apart... with a total of 30 feet of #4/0 copper.

From rods to footer to service with 2 tear drops, 1 OZ Gedney rebar grounding clamp.

EE's way.....90' of 5/8" copperclad rods, 4 Cadwelds, 110' of #4/0 copper, 3 test wells and Certified testing @ 5 ohms.

Without putting any $$ amounts it's obvious that their way is costly. Not to mention the building is being built on very small site...back of the building(where the electric room is) sits 10 feet off of the property line with a parking lot right up to lot line from the next door office building.

To get a 30 x 30 x 30 triangle we have to put at least one test well and rod inside the building.

Sorry to disagree, but it actually costs a lot more.

 

[iwire]

My thoughts.

You don't need any rods if you have the footer available

Engineers over design things

I (we) make money based on the cost of the job, so if they design it I am happy to install it.

I (we) should make more profit on a high costing job.

 

[ksmith846]

My thoughts.

You don't need any rods if you have the footer available

Engineers over design things

I (we) make money based on the cost of the job, so if they design it I am happy to install it.

I (we) should make more profit on a high costing job.

I (we) totally agree with larger job + same markup = more money in my (our) bank account.

However, I (we) prefer to provide VE options after contract because I (we) can keep our original OH/PROFIT margins from the contract total in the bank and only give the owner back the actual hard cost difference. :thumbsup:
All along looking like a hero saving the owner money:angel: Then they tend to use me in the future as I was able to help them bring their projects in under budget.