jmoore284@gmail.com
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- Location
- Evansville, IN
Has anyone had experience with lighting transformer disconnects like those from Daykin in terms of use in custom control panels that have large incoming feeders. I am conducting an arc flash analysis for a customer who has Daykin lighting disconnects in most of their custom panels. Sometimes they are mounted inside on the sub-panel while others are mounted outside to the roof of the cabinet. In one case I have a panel fed with 2 per phase 350mcm from a bus duct overhead. The total length of the incoming cables is no more than 10-15'. When the panel was buiilt they installed a Daykin lighting disconnect inside the panel and wired it per the manufacturers directions using 12 awg wire connected to the line side of the main disconnect.
In this case the Daykin lighting disconnect is mounted inside of the panel which I believe allows it to comply with the NEC tap rule. (240.21(B(1)(4) states if the conductors leave the enclosure where the tap is made the capacity of the tap conductors is not less than one-tenth of the rating of the over-current device protecting the feeder conductors. With this setup the lighting disconnect results in an incident energy high enough to make the device "Extreme Danger". By being mounted inside the panel the panel itself then becomes "Extreme Danger".
In other cases the Daykin lighting disconnects are mounted outside of the enclosure to the roof of the panel. In these cases since the tapped conductors leave the panel where the tap is made and they are less than one-tenth of the rating of the over-current device protecting the feeder conductors the wiring of the lighting disconnect does violate the tap rule.
The engineer at Daykin did not seem to know much about the tap rule or these issues that result from wiring their device per their recommendations.
In this case the Daykin lighting disconnect is mounted inside of the panel which I believe allows it to comply with the NEC tap rule. (240.21(B(1)(4) states if the conductors leave the enclosure where the tap is made the capacity of the tap conductors is not less than one-tenth of the rating of the over-current device protecting the feeder conductors. With this setup the lighting disconnect results in an incident energy high enough to make the device "Extreme Danger". By being mounted inside the panel the panel itself then becomes "Extreme Danger".
In other cases the Daykin lighting disconnects are mounted outside of the enclosure to the roof of the panel. In these cases since the tapped conductors leave the panel where the tap is made and they are less than one-tenth of the rating of the over-current device protecting the feeder conductors the wiring of the lighting disconnect does violate the tap rule.
The engineer at Daykin did not seem to know much about the tap rule or these issues that result from wiring their device per their recommendations.