Parallel Breakers

[ohmti787]

Hello, I'm trying to feed a 400A ATS from a 400A meter main combo paralleling the two outputs of the meter main. Would this set up violate article 240.8?



I'm just going back and forth with the electrician on this. He's telling me that it's alright, that he's done it before and what not, but I don't know.... it seems kinda sketchy to me.

Please let me know your thoughts.

Thanks

 

[HEYDOG]

Yes it is a violation of 240.8!

 

[hillbilly1]

You are correct, and he is not. He does not want to pull a permit and do it correctly or can’t/won’t get two 200 amp transferswitches. (Assuming your feeding two separate 200 amp panels.

 

[LarryFine]

Hint: two 200a ATSs should cost less than one 400a ATS. What is the load configuration?

 

[ohmti787]

It's an existing system. Currently the ATS feeds a MLO panel with two 150A CB's that feed two separate panels. Kinda of a mess actually

 

[ohmti787]

So, correct me if I'm wrong, but the hazard here is essentially the potential to backfeed this meter main, right?

 

[don_resqcapt19]

So, correct me if I'm wrong, but the hazard here is essentially the potential to backfeed this meter main, right?

That would not be possible per your drawing, assuming the transfer switch is correctly designed.

It is simply the performance of breakers in parallel is unknown.

 

[Jraef]

That would not be possible per your drawing, assuming the transfer switch is correctly designed.

It is simply the performance of breakers in parallel is unknown.

Correct. Although breaker manufacturers can test and list parallel breakers for higher currents, you can’t do that in the field.

Well I suppose you CAN if you were willing to spend ~$50,000 with UL for the testing and listing…