Transformer

Status
Not open for further replies.
M

mannyb

Senior Member
Location
Florida
Occupation
Electrician
480v panel feeds Xfmr to 120240 panel. The xfmr will sit between the both. I was told i need to follow the 10' tap rule going from xfmr to LV panel. Could I put panel further than 10' ? The xfmr is located indoors.
 
Is this a delta-wye transformer application?

There is feeder protection requirements in 240 and transformer protection requirements in 450.

I typically keep the first OCPD within 10' of the XFMR secondary to accomplish both.
 
mannyb said:
480v panel feeds Xfmr to 120240 panel. The xfmr will sit between the both. I was told i need to follow the 10' tap rule going from xfmr to LV panel. Could I put panel further than 10' ? The xfmr is located indoors.
Click to expand...

So, you are looking at 240.21.C.2 Transformer Secondary Conductors, not over 10"

If the installation qualifies under 240.21.C.3, Industrial Installation, that allows 25'

And there is also Part VIII, Supervised Industrial Installations, 240.92.C, which allow 100'. I use this one occasionally.

However, a secondary fused disconnect near the transformer is not exactly expensive. That allows a MLO panel.
 
ron said:
Is this a delta-wye transformer application?

There is feeder protection requirements in 240 and transformer protection requirements in 450.

I typically keep the first OCPD within 10' of the XFMR secondary to accomplish both.
Click to expand...

Sorry for late response. The feeder disconnect can be remote but the secondary needs to be within 10' and OCPD? correct? do you happend to know where in NEC where it addresses this application.
 
mannyb said:
Sorry for late response. The feeder disconnect can be remote but the secondary needs to be within 10' and OCPD? correct? do you happend to know where in NEC where it addresses this application.
Click to expand...
240.21.(C).(2) Transformer Secondary Conductors not over 10' as mentioned by iceworm
450.3 cover transformer protection sizing
408.36 covers protection for panelboards
 
ron said:
240.21.(C).(2) Transformer Secondary Conductors not over 10' as mentioned by iceworm
450.3 cover transformer protection sizing
408.36 covers protection for panelboards
Click to expand...

I have couple 45kva transformers that need to be supported in ceiling. The restaurant has limited space and the xfmr will need to sit alot futher than 10' could I install a disconnect on xfmr then feed panel ? Or is there anything I can do per NEC 2019 to be safe.
 
Status
Not open for further replies.
Top