One circuit (5-Wires) to be split into two conduits

[profiler]

Here is my problem.

I have a circuit "4-38mm²THHN + 1-14mm²THHN in 65mmPVC" and it should be embedded in concrete. I know that 65mmPVC is not possible for embedding in 150mm concrete slab. So, I would like to know if it is permitted to split this circuit into to conduits?

 

[Smart $]

Please elaborate... What is the source of the 5 wires, and what do they supply or connect to?

 

[Smart $]

Also, not familiar with building codes for your locale or metric sizing, but in US term's your looking at 2-1/2" PVC in a 6" concrete slab. Over here, there would be many scenarios where that would fly... and of course some that it wouldn't. Sparse detail makes it hard for us to provide direction...

 

[profiler]

Also, not familiar with building codes for your locale or metric sizing, but in US term's your looking at 2-1/2" PVC in a 6" concrete slab. Over here, there would be many scenarios where that would fly... and of course some that it wouldn't. Sparse detail makes it hard for us to provide direction...

The source Voltage is 400V and connected to 125A Branch Circuit Breaker. It will supply F&B area at level 2. By the way, the thickness of slab is 125mm not 150mm because it's a suspended slab.

For example, 2-38mm in 1" PVC and 2-38mm + 1-14mm in 1" PVC. The two 1" PVC will be embedded close to each other.

What would be the effect if the wires are separated into two conduits? Will it produce inductive heating?

 

[roger]

If the PVC conduits are in fact run in close proximity to each other there should be no problem with inductive heating. I would still look for another way of doing it if at all possible.

Roger

 

[mwm1752]

Non parallel feeder, all conductors in same raceway 300.3(B)

 

[roger]

Non parallel feeder, all conductors in same raceway 300.3(B)

You think New Guinea is actually under the NEC?

Roger

 

[roger]

Never mind, the OP's profile says he is under the 2011.

Roger

 

[kwired]

I have to agree that no objectionable effects are that likely by keeping them close to one another, but still doesn't comply with NEC.

Perhaps some other kind of raceway or cable method would work better, if it is a problem for the construction of the slab?

 

[profiler]

I have to agree that no objectionable effects are that likely by keeping them close to one another, but still doesn't comply with NEC.

Perhaps some other kind of raceway or cable method would work better, if it is a problem for the construction of the slab?

Thanks kwired! The structural engineer did not allow us to embed 65mm PVC so our option is to split it into two.

 

[don_resqcapt19]

Non parallel feeder, all conductors in same raceway 300.3(B)

I would appear that 300.3(B)(3) would apply...it acts as an exception to the main rule in 300.3(B).

 

[kwired]

Thanks kwired! The structural engineer did not allow us to embed 65mm PVC so our option is to split it into two.

OK, now consider to reduce inductive effects you still need to run those raceways as close as possible to one another.

How close will the structural engineer allow them to be before they have a negative effect on the structural integrity of the slab?

 

[mwm1752]

I would appear that 300.3(B)(3) would apply...it acts as an exception to the main rule in 300.3(B).

???? Please explain -- I agree 300.3(B) is an exception but I don't read into the OP how it applies

 

[don_resqcapt19]

???? Please explain -- I agree 300.3(B) is an exception but I don't read into the OP how it applies

The OP said he was using PVC conduit. 300.3(B)(3) permits the conductors of a circuit to be in multiple raceways or cables if the wiring method is non-metallic.

 

[mwm1752]

The OP said he was using PVC conduit. 300.3(B)(3) permits the conductors of a circuit to be in multiple raceways or cables if the wiring method is non-metallic.

I did not see the specific single conductor or type in the OP, which is referred in the exception. Sound like he had a three phase circuit with a grounded & grounding conductor in which he wanted to separate conductors into 2 pipes. Even in non metallic conduit I don't see it.

 

[don_resqcapt19]

I did not see the specific single conductor or type in the OP, which is referred in the exception. Sound like he had a three phase circuit with a grounded & grounding conductor in which he wanted to separate conductors into 2 pipes. Even in non metallic conduit I don't see it.

It is my opinion that this is exactly what 300.3(B)(3) permits. This section acts as an exception to the main rule that requires all of the conductors of the circuit to be in the same raceway or cable.

 

[mwm1752]

Maybe you could dissect 300.3(B)(3) so that I may comprehend the section properly. In the few years in this trade, I have never seen nor considered an installation as per the OP suggest, Have you used a similar method in your experience? My limited thinking is his installation could be any number of combinations in each pipe such as -- (a,b,n) (c,g) -- (a,b,g) (c,n) -- (a,b,c) (n,g) -- (a,n,g) (b,c) of course ungrounded conductor phases can be interchanged for more combinations.