I am trying to figure out what options are available for cable entries into switchgear and transformers on an NEC project.
We will be using both non metalclad 'Tray Cable' and non metalclad MV-90 cable. On a typical IEC project for this application I would use a brass industrial cable gland with metric parallel threads. The switchgear and transformers would have gland plates with suitably sized clearance holes, and the gland would be secured with a locknut.
The project is to be in line with NEC/NEMA standards, and I am having difficulty finding suitable cable glands (sometimes referred to as cable connectors / cord grips ?) or other suitable means of cable entry.
It seems that options include:
(1) 'Cord and cable fittings' type products such as Cooper Crouse Hinds CGB product, although this does not appear to be available in aluminium (for use with single core power cables), neither does it appear to be rated as NEMA 4X for use outdoors in transformer bay location. Appleton manufacture a similar product in Aluminium or steel material but again, it does not appear to meet NEMA 4X, and neither of these manufacturer's show the product with a locknut for cable entry into enclosures with clearance holes.
(2) Killark manufacture a cord connector (model ZS108) which is shown in the catalogue with a locknut. I have concerns about the ability of this arrangement in terms of maintaining integrity of enclosure when using tapered NPT threads. I have been told that with a tapered thread the locknut can become tight on the thread before it has formed a tight seal between the connector and the enclosure.
(3) The final option appears to be to pass the non-armoured cable through an 'insulating bushing' such as o-z gedney type ABB. These do not appear to provide any sort of seal between the cable and the enclosure, so would be unsuitable for cable entry to transformers, and since our switchgear is to be top entry they do not appear to be suitable in terms of ingress protection of the switchgear enclosure.
There seems to be limitations and restrictions with all of the above methods none appears to fully meet our requirements.
I would be grateful for advice as to how cable entry to switchgear and transformers is typically carried out with NEMA equipment and in accordance with NEC standards.
We will be using both non metalclad 'Tray Cable' and non metalclad MV-90 cable. On a typical IEC project for this application I would use a brass industrial cable gland with metric parallel threads. The switchgear and transformers would have gland plates with suitably sized clearance holes, and the gland would be secured with a locknut.
The project is to be in line with NEC/NEMA standards, and I am having difficulty finding suitable cable glands (sometimes referred to as cable connectors / cord grips ?) or other suitable means of cable entry.
It seems that options include:
(1) 'Cord and cable fittings' type products such as Cooper Crouse Hinds CGB product, although this does not appear to be available in aluminium (for use with single core power cables), neither does it appear to be rated as NEMA 4X for use outdoors in transformer bay location. Appleton manufacture a similar product in Aluminium or steel material but again, it does not appear to meet NEMA 4X, and neither of these manufacturer's show the product with a locknut for cable entry into enclosures with clearance holes.
(2) Killark manufacture a cord connector (model ZS108) which is shown in the catalogue with a locknut. I have concerns about the ability of this arrangement in terms of maintaining integrity of enclosure when using tapered NPT threads. I have been told that with a tapered thread the locknut can become tight on the thread before it has formed a tight seal between the connector and the enclosure.
(3) The final option appears to be to pass the non-armoured cable through an 'insulating bushing' such as o-z gedney type ABB. These do not appear to provide any sort of seal between the cable and the enclosure, so would be unsuitable for cable entry to transformers, and since our switchgear is to be top entry they do not appear to be suitable in terms of ingress protection of the switchgear enclosure.
There seems to be limitations and restrictions with all of the above methods none appears to fully meet our requirements.
I would be grateful for advice as to how cable entry to switchgear and transformers is typically carried out with NEMA equipment and in accordance with NEC standards.
