Two overcurrent protection protecting one device? 3

[batman2010]

Hi Guys,

I am having an electrical upgrade for a building in New York where I have a meter bank and pullout fused switches protecting each apartment panel, I was asked to provide main circuit breaker panels in each apartment for maintenance issues, is this allowed by code to have two overcurrent protection devices in a row protecting one device(panel)?
Also since these are big apartments we are providing 3 phase 200A service for each apartment, the meter bank or 'meters set' for that came out that the pullout fused switches had to be at 7'-4" high, I was told that this is high, but I can't see anywhere in the code that indicates a height limit for them?

Thank you all for the input.

 

[rbulsara]

What do you mean by two devices in a row? In series? If so, Yes.

As for height of switches and breakers, look up NEC 110.1 and 404.8. You should also look up any amendments in NYCEC.

Rafiq Bulsara

http://www.srengineersct.com

 

[batman2010]

I mean that I have a 3phase, 150A fused switch in the electric room protecting the apartment panel, and then I am going to have a main circuit breaker rated 3P-150A in the apartment panel, I thought this is against the code and you should have one overcurrent protection ahead of the device(panel)?

 

[rbulsara]

Why do you think so?

Rafiq Bulsara

http://www.srengineersct.com

 

[cranky108]

So how are you protecting the cable between the electric room and the apartment panel?

 

[batman2010]

Maybe the best way to say it is if a short circuit occurs does it matter which one will trip first? the circuit breaker or the fuse will blow?

Cable is protected by the meter pullout fused switch in the electric room.

 

[davidbeach]

There is no limit to the number of protective devices permitted to respond to a fault or other abnormality. May or may not be good design, but it will never be a code problem unless selective coordination is required. And even if selective coordination is required your won't have any code problems with multiple devices operating as long as all those devices all cause exactly the same load to be interrupted.

 

[rbulsara]

davidbeach answered it.

Rafiq Bulsara

http://www.srengineersct.com

 

[jraef]

It is not a code issue, but it is a "best practices" issue. Multiple protective devices in series sets up the possibility of confusion as to which one cleared the fault. While not inherently dangerous as long as everyone follows all of the basic safety rules forever, it does open a possibility of danger for the sloppy idiot way off in the future who doesn't. He knows the circuit is dead, ASSUMES the downstream device has tripped and works on the circuit, then someone else comes along and resets the upstream device not knowing that someone else is working downstream. Not supposed to happen, but Murphy rules and you just gave him a seat at the table.


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