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hello. I am currently working on supplying 480v 3 phase for a new peace of equipment at the factory where I work, rather than run conduit and wire from the distribution panel, to save cost they wont me to tap into the 480 feeding a transformer that supplies 208v 3 phase to a breaker panel. my question is ; can I do this according to code, and if I can , could I insert a disconnect on the primary side and run a tap from there to the new equipment. the feeder from the panel is on a 100 amp breaker
 

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hello. I am currently working on supplying 480v 3 phase for a new peace of equipment at the factory where I work, rather than run conduit and wire from the distribution panel, to save cost they wont me to tap into the 480 feeding a transformer that supplies 208v 3 phase to a breaker panel. my question is ; can I do this according to code, and if I can , could I insert a disconnect on the primary side and run a tap from there to the new equipment. the feeder from the panel is on a 100 amp breaker
Should be sweet with some crimp lugs and well aimed tek screws bro.
 

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Generally breakers feeding transformers are sized for the transformer, nothing more. Adding additional load will probably have bad results. ( generally speaking)

Also have the facility invest in a qualified engineer or master electrician to scope out the work.
It's not as simple as it sounds.
 

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hello. I am currently working on supplying 480v 3 phase for a new peace of equipment at the factory where I work, rather than run conduit and wire from the distribution panel, to save cost they wont me to tap into the 480 feeding a transformer that supplies 208v 3 phase to a breaker panel. my question is ; can I do this according to code, and if I can , could I insert a disconnect on the primary side and run a tap from there to the new equipment. the feeder from the panel is on a 100 amp breaker
How much current is on that line now?

What is the load you're adding?


Yes you can do it as long as the answer to the above checks out for you.

Welcome aboard..:thumbup:








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It's nice that people want to help but I'm not convinced this poster is qualified to do the work. I'd rather teach a HO how to hang a ceiling fan over the phone than to help someone perform dangerous work when they clearly shouldn't be. Maybe I'm jumping the gun but I have a feeling that's the case here
 

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hello. I am currently working on supplying 480v 3 phase for a new peace of equipment at the factory where I work, rather than run conduit and wire from the distribution panel, to save cost they wont me to tap into the 480 feeding a transformer that supplies 208v 3 phase to a breaker panel. my question is ; can I do this according to code, and if I can , could I insert a disconnect on the primary side and run a tap from there to the new equipment. the feeder from the panel is on a 100 amp breaker
Are you thinking or installing double lugs on the transformer? Is there a disconnect ahead of the transformer?
 

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I kind of doubt they oversized the conductors supplying the transformer for future expansion. You better make sure it can handle the additional load before tapping into it
 

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I kind of doubt they oversized the conductors supplying the transformer for future expansion. You better make sure it can handle the additional load before tapping into it
Actully there is a very good chance the conductors and breaker are oversized.

Generally the feeder to a transformer is oversized for inrush. Up to 250%.
 

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Don't know about the states but in canada the transformer OCD and conductors are rated at 125% of the rated current. And are not sized for inrush
 

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Don't know about the states but in canada the transformer OCD and conductors are rated at 125% of the rated current. And are not sized for inrush
Here depending on the specifics the primary may be as high as 300% and the secondary as high as 167%.

On the primary side this is done for transformer in rush when energizing the unit.



Now are you sure about the CEC requirements or just going from what someone told you. I doubt inrush is only a problem in the US. :)
 

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I'll look into it more when I have my book. I'm in 3rd year right now and I'm confident of those ratings but we are also focussing on 750v and less dry core transformers.

I never really thought of transformers having inrush but it makes sense.
 

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Discussion Starter #17
thank you all for your replys yhe outfit installing the equipment is requesting one 480v 3 phase 20 amp feed to the equipment.
 

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They are trying to save money on one twenty amp circuit? That's ridiculous . I would keep applications out at other employers.
 

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Here depending on the specifics the primary may be as high as 300% and the secondary as high as 167%.

On the primary side this is done for transformer in rush when energizing the unit.



Now are you sure about the CEC requirements or just going from what someone told you. I doubt inrush is only a problem in the US. :)
If you are worried about that does adding another load on the primary make the inrush magically go away?
 
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