Auto transformer install questions

[hhsting]

I have the attached auto transformer 15kVA 3 phase 208V to 240V secondary.

My questions are as follows:

1. Engineer has marked to provide disconnect on the secondary of transformer in accordance with NEC 2017 Article 422.31. I dont see how this 422.31 applies. Does the auto transformer require disconnect secondary side?

2. I looked at NEC 2017 Article 450.5 but its not clear. Does the autotransformer require grounding electrode or not?

3. Does the auto transformer require primary and secondary overcurrent protection for secondary conductors?

4. Would Table 450.3(A) apply to autotransformer for sizing overcurrent protection?

 

[hhsting]

I have the attached auto transformer 15kVA 3 phase 208V to 240V secondary.

My questions are as follows:

1. Engineer has marked to provide disconnect on the secondary of transformer in accordance with NEC 2017 Article 422.31. I dont see how this 422.31 applies. Does the auto transformer require disconnect secondary side?

2. I looked at NEC 2017 Article 450.5 but its not clear. Does the autotransformer require grounding electrode or not?

3. Does the auto transformer require primary and secondary overcurrent protection for secondary conductors?

4. Would Table 450.3(A) apply to autotransformer for sizing overcurrent protection?

Anyone?


Sent from my iPhone using Tapatalk

 

[don_resqcapt19]

1) I assume the autotransformer is used to provide the correct voltage for an appliance covered by Article 422.
2) An autotransformer cannot be connected to a grounding electrode as it is not a separately derived system.
3) See 450.4
4) No

 

[hhsting]

1) I assume the autotransformer is used to provide the correct voltage for an appliance covered by Article 422.
2) An autotransformer cannot be connected to a grounding electrode as it is not a separately derived system.
3) See 450.4
4) No

Yea auto transformer feeds appliance but that appliance is cord and plug connected?? So receptacle cant be used as disconnect?

I dont see anything in 450.4 for primary 4 wire and secondary 4 wire auto transformer??