Full Size Equipment Ground

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kpepin

kpepin

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I was wondering if there is any advantage to using a full size equipment grounding conductor. The reason I am asking is because the project I am working on specifies the same size EGC as the Current Carrying Conductors. For example, one panel we are feeding is a 600A 480/277 Panel and the plan shows 2 parallel sets of 350 MCM with a 350 MCM EGC (5 350MCM total in each 3" EMT). I was just wondering what kind of benefit this has when the NEC allows a #1 EGC.

A little background to the project: A High School Addition, each 480V panel feeds a 208/120V panel (through transformers) - each containing a lot of Isolated ground receptacle circuits.
 
Re: Full Size Equipment Ground

No, there is no real advantage to over sizing the EGC since it is not a current carrying conductor under normal conditions. Under fault conditions, the current will be much higher but not last for a significant amount of time.

If someone wants to oversize the EGC, it should only be just one size unless it were for voltage drop. If the phase conductors were up sized for voltage drop, the Code requires the EGC to be up sized by the same percentage.

With all that said,it is not a violation to use a full size EGC. :D
 
Re: Full Size Equipment Ground

As Charlie says there is no advantage. Still doesn't make any difference if IGR is being used or not. Only place I know of using full size can be beneficial is the grounded circuit conductor in 3-phase circuits. It counters the effect of overheating from harmonics and minimizes N-G voltage drop.
 
Re: Full Size Equipment Ground

I usually specify EGC to be the same size as the phase conductors. Gives the EC something to take exception to. lets me know he actually read the spec and looked at the drawings.

:)
 
Re: Full Size Equipment Ground

Originally posted by petersonra:
I usually specify EGC to be the same size as the phase conductors. Gives the EC something to take exception to. lets me know he actually read the spec and looked at the drawings.
:)
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I hope you are kidding as this practice IMO is unprofessional.

If the EC does not question it do you bring it up or do you let it ride and let the customer pay the extra cost for your peace of mind. :roll:
 
Re: Full Size Equipment Ground

I think everyone is missing the point. If this isn't a California contract I'd wager somebody's taking lessons from us. In my state the schools are actually begging for money to buy books. I'd also wager the engineer who's wasting this money is a specialist of some sort and making five times what the drawings are worth.

This isn't just electrically irresponsible it's primarily fiscally irresponsible. Good thing it's the government because the rest of us couldn't afford to do it like this.

Hmph.
 
Re: Full Size Equipment Ground

First off, I consider it irresponsible and unprofessional for the EC to wire things up any old way he feels like regardless of whats in the spec and the drawings.

As for the extra cost, there is no extra cost if they bother to actually read the specs and drawings. If they don't catch it, they don't get the project.

I also have them run spares. Do you think its irresponsible and unprofessional to add that cost to a project as well?

I also make them run a green wire instead of allowing the conduit to serve as the EGC. That also adds cost.
 
Re: Full Size Equipment Ground

Originally posted by petersonra:
First off, I consider it irresponsible and unprofessional for the EC to wire things up any old way he feels like regardless of whats in the spec and the drawings.
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Without a doubt I agree with that entirely, I would add close to criminal in some cases.

Originally posted by petersonra:
I also have them run spares. Do you think its irresponsible and unprofessional to add that cost to a project as well?

I also make them run a green wire instead of allowing the conduit to serve as the EGC. That also adds cost.
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No I would not consider that unprofessional as that adds value for the customer.

The full size ground to test the EC does not add value to the job, it is only for you.

There are plenty of ways to make sure the EC follows the specs without trying to trap them. ;)

Just my opinion and who knows, maybe the things I catch in the specs or prints have been traps. :p
 
Re: Full Size Equipment Ground

kpepin

Any chance that the 'extra' full size conductor is supposed to be a Neutral not an EGC?

You mentioned a lot of IG loads in this panel which suggest computer loads. Perhaps the engineer wants a 200% rated neutral, that is fairly common on the jobs I work.
 
Re: Full Size Equipment Ground

Keep in mind too that the stuff I do is industrial controls oriented.

Lowest installed cost is important but it will not make or break a project. What kills me is rework. Even if the EC is paying for the rework, every day lost in the schedule is horrendously expensive.

I really do try to make the EC a partner in the process, but often I have no way to judge the relative capabilities of the contractors the end user has prequalified.

Most of my specs will start off with an invitation for the EC to propose alternatives that they feel are acceptable yet would save cost or schedule. I find that most are pretty canny about such things, and I usually go along with their suggestions.

Contractors that actually propose usefull suggestions are more likely to be considered rather than the absolute lowest bidder. I have been burned enough by the lowest bidder that I try to find reasons not to use them. When you skin out every nickle and dime to get down to the lowest price, I know that the guy will be sending me change orders to sign 3 times a day.

The last 4 or 5 years, it seems that the trend has swung towards the end users having a single contractor they use (and pay directly), and often there is no bidding at all.
 
Re: Full Size Equipment Ground

I think Bob (Iwire) has hit on what may be a misinterpretation of the specs. It is very unusual to see a full sized EGC, and a lot of people do confuse the terms for grounded (neutral) conductor for EGC.

Pierre
 
Re: Full Size Equipment Ground

They are asking for a full size EGC not neutral. One of the prints shows exactly what they expect and there can be no mistake about it. The spec also reads "Equipment Grounding Conductor" not "Grounded" or "Neutral"
 
Re: Full Size Equipment Ground

kpepin, if it is in the spec and bid to spec, by all means install it. Nothing in the code to prevent it.
 
Re: Full Size Equipment Ground

Kpepin

You stated that this feeder is feeding a 600 amp/ 480/277 panel?

I have to ask how do they think you will be able to supply the 277 volts in a code compliant way if you don't run a neutral?
Something is missing.
 
Re: Full Size Equipment Ground

Originally posted by hurk27:
Kpepin

You stated that this feeder is feeding a 600 amp/ 480/277 panel?

I have to ask how do they think you will be able to supply the 277 volts in a code compliant way if you don't run a neutral?
Something is missing.
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I never said there wasn't a neutral. Read the original post, 5 wires per conduit. 3 Phase, Neutral, and Ground.
 
Re: Full Size Equipment Ground

I say ask about it via an RFI, but they still say install it...then let it go. It won't be your problem then if something goes wrong, because you didn't install it as requested.

I don't think it's practical, but that's just my opinion on that matter. ;)
 
Re: Full Size Equipment Ground

Originally posted by iwire:
kpepin

Any chance that the 'extra' full size conductor is supposed to be a Neutral not an EGC?

You mentioned a lot of IG loads in this panel which suggest computer loads. Perhaps the engineer wants a 200% rated neutral, that is fairly common on the jobs I work.
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Thats a good idea Bob, but I've never seen 480/277V computer loads. He did say IG loads are being served, but through a transformer at 208/120. The double (200%) rated neutral would be from the secondary of the "K-13 rated" transformer to the panels.
 
Re: Full Size Equipment Ground

Originally posted by bonding jumper:
Thats a good idea Bob, but I've never seen 480/277V computer loads.
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What? you have not seen the new 277 volt desk top PCs? :eek:

Oh well, I tried. :eek:
 
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