Busbar Risers For Tap Off Feeds

Depending where you are, you local code will dictate the requirement you need. The NEC would require that your busbar be determined on the calculated load which may be the connected load or something less. For example if your load was all motors and all running at the same time your connected and calculated load would be the same. It only half of the motors were running the the calculated load would be 1/2 of the connected.

Quote " Is it ok if the busbar rating more than the incomer breaker rating considering the increased voltdrop value."

I am not sure what you mean. Why would the voltage drop be more if the busbar rating is larger that it needs to be. It should be less.

Thanks for your reply. To make it more clear. I have to dissipate the entire load of a 2000 kVA transformer around 200m away through busbar then the voltdrop is a problem. Considering the voltdrop I require the busbar rating more than the Total Connected load Amps. No Motor load is been fed from this.

My Qn is there any technical problem in having a Busbar with higher rating and incomer less rating. I think its the same as increasing the cable runs if the length exceeds due to voltdrop and incomer breaker rating not been enhanced.

Please give your valuable reply

Thanks

There is absolutely no reason why you can't increase the bus-bar size. Most manufacturers will give recommended sizes depending on your situation. Increasing the size needlessly is just throwing away money!

Thanks for your reply, My requirement is of Cu Busbar with 510 kw Total Connected Load (no Motor loads only general lighting and power) to be fed at a length of 398 m, only one tap off reqd at the end. This is my worst case.

Please can you tell me the I/c breaker rating for the bus bar. Volt drop can be around 3 % max as per authority.

Thanks

The busbar can be maximum same size as breaker, more is a waste of money. Only exception is if the voltage drop is more than 4%, in this case you need a busbar with more cross section (more rating).

If you give me the rating of breaker, assuming 200 m lenght, I can give you the voltage drop of the line using our busbar catalogue.

I suggest to use in any case aluminium conductors.