Cable Selection for MCC

Please consult the relevant IS (or other adopted standard) that applies locally. It will have tables and/or formulas based principally on amperage, with corrections for various temperatures and cable configurations.

50 or 60 Hz?

What is your total load connected?. and What is your incoming current capacity?

this is my method

We get this question at least once a week.

American Wire Gauge table and AWG Electrical Current Load Limits ...

...and there is a signpost to British Standard 7671 here every week.

It is a considerable surprise that an organisation that makes MCCs has no discernible reference standard to work with at hand!

The OP is clueless.

Is that so?

Simple to sort out, have a guess. I been doing it for the last 40 years.

Or there's the what cable have we got kicking around method. It'll do for now.

Sir,

Your question's wording sounds like you want to size the feeder to the MCC. There are a couple ways to do this, but the safest (and probably most expensive) is to size the cable capacity at the size of the MCC's main bus. Next is to size them for the disconnect that feeds the MCC. The minimum would be to write down the data for all the motors the MCC supplies as well as which ones start simultaneously. Select the largest motor or the total of all that start simultaneously--whichever is greater--and multiply this by 1.25. Then add all the rest, and then figure a reasonable safety margin for future growth or changes. This margin is the tricky part, but should include the sizes of all MCC sections with "spare" units and allow for the percent of empty spaces that have been included for future growth.

At this point, I hope you are beginning to see why your question really should be left to people who have a fair amount of experience in the field. So, my final answer is to suggest you have someone with more experience and knowledge LOOK at it and then tell you the size needed. Of course, this could be a homework question???

--JMM

Dear Mr. RAJ ARYAN DEV.

CR4 is a TREASURE. From the link given below you will get all your doubts cleared and further add to your knowledge.

http://cr4.globalspec.com/search/sitesearch?do=show&srchobjs=t%2Cc&order=asc&fs=12&sort=textmatchrank&srch=CABLE%20SIZE%20SELECTION

DHAYANANDHAN.S

Obviously someone had to specify some sort of rating if they have the MCC.

1. What is the amp rating on the MCC?
2. How many motors will be connected to this load center?
3. What are the motor ratings?
4. What is the length of wire runs to the motors?
5. What is the distance of the MCC is from its feeder?
6. What is the rating on the MCC feeder?

Look not only at the size of the load you currently have to be controlled but also at what may be added in the future and size accordingly!
BA