hey guys great site,I might stick around.

but I have an urgent question for now.

I have a 208v, 3 phase, service lateral
(pad mount xformer secondary) feeding a 1600 Main breaker switch board.
In the past the utility company has run the secondarys, now they are requiring the customer to provide them.
The local utility had always undersized them IMO. Now that we must provide them, am I right in assuming that we must size these greater than the service main, in this case 4 sets of 500 MCM cu. ?

The project engineer tells me to run 4 sets of 350 MCM, however it is my opinion that this does not meet the NEC and 500 MCM conductors are required.

I hope I was clear with my question. and thanks in advance..

Even 4 sets of 500kcmil is not adequate. 500kcmil is only rated for 380A at 75C (the rating of the terminations in the service gear). Above 800A you are not permitted to round up.

JBD is right again. 4 sets of 500 kcm is good for 1520 amps. You will need 4 sets of 600 kcm at 420 amps for a total of 1680 amps as per 240.4C.

Is there any chance that these are still _specificed_ by the POCO using their sizing rules, even though they are to be installed by the customer's electrician?

-Jon

Correct you are about 600 MCM. I'm not doing my own math here.
The laterals were not specified by the power co. The project engineer specified the laterals on plans. Later admitting that they resized the MDP during the design and forgot the increase the service laterals.
The engineers later asked for change order pricing to increase to 4 sets #500MCM. ( thats where I got the #500). Now the owner has said he will not approve any additional funds. So the engineer has stated my change order request will not be approved. I am concerned about my liabilty in this issue due to not meeting the NEC. This project has turned very bad due to some other issues with design oh which I am taking a beating due to the engineer's faults. I really do not want to butt heads with the engineer and harm a relationship for future projects, But I do not think I have a choice. Anyone else have any ideas ?

Gee, the engineer admits his mistake here and does the right thing by asking you to submit a change order.

So now he is in effect saying, "my mistake will come out of your pocket, not mine".

The engineer has Errors and Omissions insurance that would cover his mistake if he can not come to an agreement with the owner.

Whatever happens you should not entertain the thought of making the correction at your expense even if this strains your relationship with this engineer.

Roger

What is the actual calculated load? If it is 1400 amps or less, install a second service disconnect and the 4 sets of 350.
Don

Don has a great idea here.

You could go with two 800 amp service disconnects eliminating the need for GFP and allowing the use of the 350s or 500s depending on the calculated load.

Watch out for 240.21(C)(4). This would have you terminating in a single overcurrent device.

240.21(C)(4) does not apply to service conductors.

Check out 240.21(D)

Bob

That was a test Bob. I don't follow your code reference (240.21(D) ) but if this is a Service, and when I read the first post, I see that it is then the proper code reference would be 230.71 and Don's recommendation would be valid.

"So the engineer has stated my change order request will not be approved. I am concerned about my liabilty in this issue due to not meeting the NEC. "
You can not install equipment that does not meet code regardless of the change order. I think its the engineers problem to solve and work out the problem with the owner.

"This project has turned very bad due to some other issues with design oh which I am taking a beating due to the engineer's faults."
You should not take a loss because of an error by the engineer. Had he got it right the first time you would have bid higher using the 600 kcm. He needs to step up and explain the facts to the owner.

I've changed my mind. If the utility company installs their own conductors either with their own people or subs the job out to a contractor and they are the utility company wires then the size is under the specs of the utility company. If the job is specified by the engineer or architech and the conductors are owned by the owner then it is under the NEC and I think the size and disconnecting means is under the local inspector's authority.

I can't speak for any PoCo but everyone I've dealt with absolutely demands that the customer build the infrastructure and then DEED IT OVER FREE to the PoCo. They always want to own every component right up to the main point of entry.

In my area the AHJ inspects the secondary raceways from the Poco. He does not inspect the conductors that go into that raceway. It is up to the Poco to 'get happy'. They're the ones calling the shot.

Don't even waste your time calculating these feeders. Until the Poco gets happy the owner gets no juice. They won't even land the wires on the XFMR. BTW, no EC is allowed to land those conductors at the XFMR, don't even dream of it.

Let the owner know what is what and make the Poco the heavy.

"The project engineer specified the laterals on plans. Later admitting that they resized the MDP during the design and forgot the increase the service laterals."

This sounds like the customer is the owner of the service and not the utility. I've never seen an engineer spec a job for the utility on his plans.

Bob

In California it is a universal condition of service that the Poco owns -- total clear title -- the conductors as a condition of service.

Check the fine print. You'll find that boilerplate in all utilities. Why? The MPOE is the legal liability cross over point.

The print just doesn't matter.

BTW, the secondaries on the EE's print were almost certainly transcribed from the ulitities' print. The 'committment letter' is not typically shared with the field troops. Many electricians have never seen one since it will have been sent to the EE. He is expected to incorporate their requirements in his prints.

Now our buddy screwed up, maybe. The owner is trying to shirk the tab.

Make the Poco the heavy. Put it to them, what size conductors are now required?

BTW, our Poco has these values already posted to their 'book'. You might be surprised to find that they will not require any increase in conductor size. Generally the Pocos use undersized conductors relative to the NEC.

Simply put only the Poco calls the shot. No one else, and you're not getting around them. But their conductor sizing is normally quite favorable. Don't sweat it.

Hey guys thanks for the response's,

Just to clarify. Until recently here the PoCo's always supplied the lateral conductors in customer supplied conduit.
Lately they seem to be trying to change this by way of offering metering at the xformer.
Now when the project is metered at the transformer the customer must supply the lateral feeders.

Now once again, my question remains. If I install these laterals, am I bound by the NEC ?

If so isn't 4 sets of 350MCM cu ( 4-3" PVC conduts) insuffcent for a 1600 amp main breaker in the service disconnect as per NEC 230.42(B)? (Service is already set in place)
I do not have load calculations on this project from the engineer.

Can someone define Specific Installations as referanced in 230.42?

The 1600 amp main does have an adjustable trip setting. Would it be acceptable to just turn down the trip setting to an accpetable level (less than 1200 amps) Whats to keep someone from turning it up in the future ?

Thanks Again

http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=print_topic;f=11;t=000658
Discusses the meaning of "Specific Installations"

-Jon

I have never seen a meter mounted directly at a padmounted transformer.

Could you get us pictures?

You seem to be describing a most unusual service. The CT zone within the big switch box going unused, since a separate meter and CT can will now be mounted at the pad. I find that set up hard to imagine.

Utility side arrangements are outside the scope of the NEC. Period. Their control extends up until the customer's first disconnecting means.

The meter's location does not change that.

Since there is no national code to tell the Poco what to do, they call their own shot. Out west the industry has banded together to form EUSERC, a standards committee.

I would log on to the utility website and poke around.

Even better, place a phone call. If you install anything they don't accept....

BTW the AHJ and Poco have long ago decided the turf war. You can ask either as to where they draw the line.

This metering at the xfmr. is odd. Usually you have to have a CT metering compartment in your switchgear.
You could offer to provide a termination compartment per USERC standards and pay the utility to install cables to that compartment, The termination compartment would be the designated point of service termination. The AHJ would only have jusidiction from there into the building.
Some utilities get nervous about having too many sets of large conductors terminated on the xfmr. spades. If the pad settles the secondary bushings leak because they are supported by the cables. Sometimes those utilities require a termination vault near the xfmr.

The reason you feel they "undersized" the conducts is because the utility co goes by different ratings then we do.
Our ratings come from NEC, they are not governed by NEC.

My helpers father is a line super-intent for the power co down here and this is as he explained it to me.

Commonly they will only run 2/0 for a 200amp service. I think he might only be thinking of a service drop due to it can dissipate heat very effectivly but what he says.

However the other local power co runs 4/0 for 200amp service go figure.