Power Cable In Parallel

Based on this and your previous post, I recommend you for further training/education. That, or sit back and leave your consultant alone.

Dalton,

Your question indicates that you have no idea about codes, or standards.

Good engineering requires that the design be safe and completed by competent technical people. That is not you.

You demand an answer to your question but will not have any idea of the technical merit of any answers that come from an anonymous forum. In other words, you will still be lost.

You, apparently hired a consultant to do the design. Don't meddle, interfere or otherwise try to out-think the professionals.

As I said, get out of their way and let them do what they were hired to do!

You can go back to counting beans.

And why would it trip? Start thinking it through and describe it below, Mildred.

The consultant will be applying the local code. So why are you asking this lot to disagree with the consultant, Murphy?

That is just hilarious. You would rather have your head above the parapet than the consultant's? Don't be ridiculous. Install what the consultant says and be done with it. This is not the place to chop a few quid out on some crusade.

It is not for me to say which code to work to. You started this thread. You must know which national electrical code the consultant is working to, surely?

If you have to ask, sit on your hands until the project is complete.

Sounds standard, for the information provided.

A service main with branch/phase over-current protection...ff any one of those phases were overloaded and you had to wait for the service main to open you might let all of the magic smoke out of those feeders.

Actually, it doesn't sound right to me. If there are 16 cables in one phase, it is the main breaker's protection that covers those cables. If you split them into 4 sub-groups and put a smaller breaker in each group, suppose one trips - it just opens those 4 cables. They are still connected at the main breaker end, and connected at the load end. The fault that caused the group's breaker to trip is not isolated, and the other 12 cables will get overloaded by carrying all the load current! I don't think this is a good idea.

Until their breakers trip as well.

I think we need a complete circuit diagram.

Code requires parallel conductors to be grouped together and exactly the same length. when they are is groups of 4 I suspect they take different paths and different lengths.

Do we assume the 16 cable runs end in the same panel, on a common point? It may be that the sub panel actually has multiple circuits.

Personally, I think for this sort of current they should be looking at low Z bus duct, a single certified assembly, with perhaps a single breaker.

you are right and that is my point too. if 1 breaker will trip for what ever reason, the load still have supply because of the remaining 3 circuit breakers and the 12 cables will carry the current of the 4 cables which circuit breaker was tripped. if keep unnoticed it will overload the 12 cables and you what will happen next.

The 4 sub panel breakers need to have a common tie point. All 4 will trip any one does

thanks for your kind suggestion. our consultant is not an electrical engineer by profession. He is mechanical engineer whose expertise is in clean room design.

WTF!!! You have a mechanical engineer with an expertise in clean room design doing high current power distribution design.

Sir, you need an enema.

Hire an electrical engineering consultant or a licensed electrician that knows the appropriate wiring codes for your location. The design of a power distribution system that interrupts at 2500 amperes per phase should not be designed by amateurs.

This sounds like the blind leading the blind.

Look out for the fire ball.

<UNSUBSCRIBES, IN A FLASH>

This just raises further questions! Is your consultant even qualified for such a high power electrical project design?

I've changed my reply to the last time you asked this question.

http://www.youtube.com/watch?v=-HQ5ZbaMJ-w

i was foxed by this thread, and have been following with interest the various viewpoints. My initial reaction remains - why does one use multiple CBs to protect individual cables of a phase ? The multiple cables will not exactly share the current, so how does one set the thermal trip threshold ? And, as the OP says, if one trips, the others will get overloaded and all will trip anyway. So what has been achieved in reality ? This is overload protection only. If there is a short-circuit, the big CB will trip and protect anyway. So, i just can't see the need for multiple CBs. Are we sure that the consultant is correct ? In my country, remuneration of such consultants is usually a percentage of the order value, so if they are unscrupulous, they will overspecify. i hope that is not the case here.

Maybe the OP doesn't recognize that these are actually electrical branches going to multiple loads in the same machine. Maybe the mechanical engineer designing this electrical power distribution is trying to be overly cautious because he knows that he is out of his element. Maybe the multiple ganged(?) smaller breakers mechanically fit the pre-existing local distribution panel box and will also act as a local safety disconnect instead of having to hike over 150m and impose LOTO safety protocol on the 2500A breaker for servicing. Maybe the electrical service provider requires this for local codes. Maybe some of these devices are not breakers that trip on current but are actually service disconnect switches.

to redfred, the 1 line (phase) parallel cables we are discussing about is a supply cables for sub-distribution panel in another building which is approximately 150 meters from main distribution panel where the substation is located.This sub- panel has sevral load load like Water Chillers. AHU, Compressors, etc. In attached SLD the 4 MCCB are the one I questioned (Total of 8 over all) if really necessary. Our original consultant did not recommend this system because he recommnded Bus way but when he resigned our Contractor redesigned it using cables because MAgement want to save cost and our present Consultant approved it. My rule as electrical maintenance is pure recommendation and the final decicion is w/ our present consultant. this is to make the matter clear. But to remind you all my original question was "IS this MCCBs REQUIRED by any CODE IEC w/c we practice here or NEC or BS w/c we also recognised.

Buy the codes and read them.

Maybe hire an electrician, too.

I see only basic contacts in both of these hand drawn one line drawings. This implies to me that something other than the current overload condition is why these breakers acting as disconnects exist.

I'll repeat now my earlier unanswered question. How much could you possibly save by not including these breakers?

I find it amusing but not surprising that your first consultant resigned from this project.

Good Luck getting this project safely completed under budget.

I think this discussion is hopeless.

Dalton is a bean counter, in a company run by bean counters, apparently.

This speaks volumes about the whole deadly project, "MAgement want to save cost and our present Consultant approved it."

So, management wants it to be as cheap as possible and the contractor redesigned it that way.

It is apparent that no one possesses the relevant codes, nor knowledge of them, and they are too cheap to hire an electrician or purchase the codes. and read them.

I suggest that this is another case of untrained managers trying to save a buck.

This project is in Saudi Arabia 1 Core Cable vs. 4 Core Cable I believe, and is not Dalton's first brush up against not knowing what to do or how to do it.

I'll stand aside and observe the foundering from a safe distance here in the USA.

http://fsymbols.co/pictures/5/-man-arrested-after-throwing-dinner-at-mcdonalds-worker-lol-or-wth-5596.jpg