cables for A circuit can be in 2 separate raceway

[TMMB]

There is a circuit 380 V , consists of 5 single core cable 500 mm2 for each phase and N ,it mean there ara 20 snigle core for this circuit, can we install it in 2 separate cable trays , or must on the same cable tray

is it permitted to install it on 2 cable trays according to NEC?

Please help

 

[dicklaxt]

I've done a lot of cable tray loading but it's been a while,,,need to think and research this one 5/phase @ 380v whew,how you going to terminate the ends? You got something special going on?

dick

 

[TMMB]

yes there is special accessories from the manufacturer will solve the termination issue but i'm asking, it is permitted to lay conductors for a circuit on separate cable trays according to NEC or not ??

 

[augie47]

Seems it would be difficult to comply with 310.4(B), but that said, I have not found specific wording prohibiting it.

 

[TMMB]

let me ask in general , can we split conductors for a circuit to install in 2 different raceway

 

[dicklaxt]

I don't have any reference material so I'm talking off the top of my head but I think they have to be lashed together but,,,,,,,, let's look at what the OD on a 4/c 500 would be. I'm thinking 2.5 to 3 ",then use 1/4 diameter separation between groups.Using 3" and .75" and extending the math I come up with a total of 18".Why do you need two separate trays? I know thats not the answer to your question but maybe some help.I also think at that voltage class they can be random lay stacked.No now come to think a bit they are too large to stack,I believe the limit is at 4/0 AWG if memory serves me.

dick

 

[TMMB]

let me ask in general , can we split conductors for a circuit to install in 2 different raceways ??

 

[dicklaxt]

If I read it correctly ,2008,,310.4(C) allows it to be in separate raceways but believe it to say you must have the same number in each raceway and 5 divided by 2 may shoot that idea down.

dick

 

[augie47]

let me ask in general , can we split conductors for a circuit to install in 2 different raceways ??

IT is commonplace to install parallel conductors of a circuit in separate raceways as long as each phase, grounded and grounding conductor are in each raceway. The provisions of 310.4 mist be taken into consideration.

 

[TMMB]

the OD for each conductor = 37mm then 16x37 =592mm so i need 600mm if it touched , but if i need distance = 1D so i need more than 600mm cable tray , but the available is 600 mm only , so im asking if we split it to 2 different trays , is it permitted as per NEC or not?

 

[dicklaxt]

2008,,,,392.8(D) says they must be bundled together in groups one conductor/phase .

diick

 

[kwired]

Lets consider reasons why NEC wants all conductors of a circuit in same raceway, cable, etc. or in close proximity in direct buried or in free air conductors.

Conductor impedance. If you run one conductor of a circuit through different path than the others, that one conductor will have a different overall impedance than the others even if it is same size, length, etc. If it passes through or by objects with magnetic properties the fact that equal current is not returning in a close by conductor means there is no cancellation of magnetic fields and it will induce magnetic fields on these objects - which will change the overall impedance of the conductor, and introduce inductive heating in the magnetic objects surrounding it. Not having the return current in a nearby conductor alone does change the overall impedance of the conductor.

Even if the change of impedance seems negligible for normal loading, it will be increased many times during fault current conditions. Higher impedance of the circuit during a fault means longer fault duration before operation of overcurrent protection. Although there are times when we want to reduce available fault current - this is not the way to do it.

About the only place I am aware of where NEC allows you to run a circuit conductor in separate raceway from other conductors of the same circuit is for underground parallel conductors in non magnetic raceways - but I'm pretty certain you must still have other conductors of the circuit and their raceways in close proximity.