conversion of a 800A CB to two 800A CBs to prevent frequent tripping

[vmac100]

folks,thanks for the great job.i've really had alot of insight since i joined this group.
please,i have a major project that i am handling right now and i need some assistance.
we have a CB that frequently trips due to overload.what i want to do now is to split the loads between two CBs of 800A rating.i also plan on transfering just the vital loads to the new CB while leaving the Non-essential loads on the present CB.
I need advice as to how feasible this is as the CB is in a panel,the safety implications and possible design procedures.thanking you all for the expected assistance.

 

[jOmega]

When you split the loads, do you think it might be a good idea to re-size the breakers to the actual loads/circuits they are protecting ?

With all loads on one breaker.... the breaker is sized to the sum total of all the loads ...

When you split the loads..... each load will be a lesser amount... and so, 800 amp bkr would seem to be very much oversized...

 

[dede61]

Hello vmac100,

What is the load now on this single CB, If not exceeding the max load of the CB then how come youre CB trips ? is the protection relay well adjusted for the load ?

regards,

Danny.

 

[busbar]

Somewhere in the work, it may be a good idea to perform primary-current injection tests on the breaker exposed to repeated overload conditions.

Careful review of the upstream components serving the reconfiguration is likely in order, including evaluation of short-circuit withstand of new/modified components.

 

[DanDel]

vmac100, how are the loads connected to the existing 800A C/B? Does it feed another panel/panels or are they tapped off of a cable or bus or what?
If you add another 800A C/B to the panel that your existing C/B is in, you must remember that any cable connected to each C/B must be rated for 800A.
If you have 800A+ of multiple loads connected to the existing C/B, and you are planning to separate these loads, I am curious how the loads are connected.

 

[sngpl]

I guess a better approach would be to get a bigger properly sized circuit breaker!

 

[jbartos]

Suggestion to vmac100 (Electrical) Nov 3, 2003 marked ///\\we have a CB that frequently trips due to overload.what i want to do now is to split the loads between two CBs of 800A rating.
///The split does not necessarily have to be 800A and 800A. It may for example be 800A and 400A; especially, if the upstream protection is less than 800A+800A=1600A\\i also plan on transfering just the vital loads to the new CB while leaving the Non-essential loads on the present CB.
///Yes, this is often mandatory\\I need advice as to how feasible this is as the CB is in a panel,
///If there is a room in the panel, then another large circuit breaker may be added. If not, an enclosed circuit breaker, as a minimum, will be needed. If more branch circuits are expected, additional panel will be needed.\\the safety implications
///The protective devices are supposed to be adequate and selectively coordinated.\\ and possible design procedures.
///It is a good idea to find out the current demand. Then, add some suitable margin for the load growth.\\

 

[vmac100]

thanks folks.that was quite helpful

 

[uno]

Also check whether the breakers are properly derated for ambient conditions. A 800A Catalogue specification may not be suitable for your site.

Also I think the cable sizing per breaker rating is specific to NEC Projects. May not be true in the IEC world.