Multiple layer of conduits

[m sleem]

I?m in a hospital project where the wire type as per specs min 4mm2 CU/XLPE/LSHF & the overall diameter for each wire 7mm, by applying table9 the allowable fill ratio will be 40% & each conduit would fit only three wires (one circuit), some of the electrical rooms receiving approximately 500 conduits & the reasoning of this large number is the application of the smart lighting control where each circuit splitted into multiple channels (at least three), appreciate your input regarding the following solutions in order to reduce the conduit number:

- Change all wires to min 4mm2 CU/PVC & that would reduce the number of conduits by 50% approximately.
- Change all wires to min 4mm2 CU/PVC for circuits & (1.5 to 2.5 mm2 CU/PVC for lighting channels) & that would reduce the number of conduits by 61% approximately.

- Maintain all wires As Per Specs to 4mm2 CU/XLPE/LSHF for circuits & (1.5 to 2.5 mm2 CU/XLPE/LSHF for lighting channels) & segregate the installation between normal and emergency wires where the normal wires will be installed in perforated cable tray size 600x150mm & the emergency wires will be installed in #200 conduits & could be reduced to #100 conduits if use CU/PVC wires. See the below installation, appreciate your patient & ideas.

 

[Smart $]

The installation is using wiring methods not recognized by the NEC. In that sense, the whole installation is non-compliant. :blink:

One aspect of your proposed change which stands out is reducing the size of wire for lighting zones. Unless there is OCP to protect those conductors at their ampacity, that's a no-no under the NEC. The only permitted reductions in wire size (ampacity) for lighting branch circuits are taps, and these are limited in length (relatively short, such as 6' fixture whips).

Another aspect is running single conductors in cable tray. Under the NEC only certain types of single conductors can be run in cable tray... essentially they have to qualify as a single-conductor cable and typically much larger than the size you are dealing with.

Being your issue is with job spec's, the best you can do is run any proposed change up the ladder...

 

[m sleem]

The installation is using wiring methods not recognized by the NEC. In that sense, the whole installation is non-compliant.

Would that mean the accepted installation of each single conduit shall be either surface/suspended separately & no multiple layers?

One aspect of your proposed change which stands out is reducing the size of wire for lighting zones. Unless there is OCP to protect those conductors at their ampacity, that's a no-no under the NEC. The only permitted reductions in wire size (ampacity) for lighting branch circuits are taps, and these are limited in length (relatively short, such as 6' fixture whips).

For this type of lighting control system each single channel is protected by the power supply unit which could be 6A, 10A OR higher, unfortunately this type of lighting control is not discussed in NEC.

Another aspect is running single conductors in cable tray. Under the NEC only certain types of single conductors can be run in cable tray... essentially they have to qualify as a single-conductor cable and typically much larger than the size you are dealing with.

In IEC std the single core cable starting from 4mm2 0.6/1kv (douple layers e.g pvc/pvc, xlpe/pvc, xlpe/lshf) which can be installed in cable tray typically the proposed installation.
Appreciate your feedback!

 

[Smart $]

Would that mean the accepted installation of each single conduit shall be either surface/suspended separately & no multiple layers?

For this type of lighting control system each single channel is protected by the power supply unit which could be 6A, 10A OR higher, unfortunately this type of lighting control is not discussed in NEC.

In IEC std the single core cable starting from 4mm2 0.6/1kv (douple layers e.g pvc/pvc, xlpe/pvc, xlpe/lshf) which can be installed in cable tray typically the proposed installation.
Appreciate your feedback!

What I meant by my first sentence is that you attempting to adapt equipment and methods not recognized under the NEC to make a compliant installation. The NEC does not recognize wire sized to metric standards or insulated conductors and cables that are not listed types. However, NEC concepts can be adapted, and it is up to the AHJ for ultimate approval.... just leaves quite a lot to AHJ discretion.