Transformer and panel install questions

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iwire

Moderator
Staff member
Location
Massachusetts
The OP is serving out 120V from existing system as he stated.

If the preponderance of the equipment from this new panel is 240 then my solution will give him the lowest cost trafo solution.

Should he need some 120 out in the future then use a buck-boost xfr for that to buck it down.

This is cost driven by manufacturing volume since the 208 is the popular heavy hitter sales-wise.

Correct me if I am wrong here. We want the optimal solution - cost (parts $ labor), serviceability, reliability, ease of installation.

This is a hack way of doing it.

It makes no sense at all.
 

dionysius

Senior Member
Location
WA
This is a hack way of doing it.

It makes no sense at all.

NEMA transformers have these taps for this purpose. I suggest you talk to one of the manufacturers and you will find confirmation to the approach.

Why do you think these primary taps are provided to begin with???? It costs money to do so.
 

Fnewman

Senior Member
Location
Dublin, GA
Occupation
Sr. Electrical Engineering Manager at Larson Engineering
NEMA transformers have these taps for this purpose. I suggest you talk to one of the manufacturers and you will find confirmation to the approach.

Why do you think these primary taps are provided to begin with???? It costs money to do so.

Not all transformers have primary taps. When they do, they are there for adjusting the secondary voltge(s) to a standard 120/240, 480/277, etc. when the utility voltage in the area of use is not nominal. Where the POCO voltage varies frequently, automatic tap changers are often employed. P.S. - I agree with dionysius!
 

florida-sparkey

Senior Member
Location
Pinellas Park, Florida
Occupation
Master Electrician
Thank you, Thank you and Thank you!

I am asking the final follow up question and one that caused me to write the OP. Could anyone give me the thumbs up or down on my AIC calc?


My concern is my calculation with AIC at the new panel main breaker lugs fed by xformer secondary.

I need to confirm that I can use a 10K rated (most likely it will be a 22 or 24K, cause that's how most 3P panels come in the brands I use)
 
Thank you, Thank you and Thank you!

I am asking the final follow up question and one that caused me to write the OP. Could anyone give me the thumbs up or down on my AIC calc?


My concern is my calculation with AIC at the new panel main breaker lugs fed by xformer secondary.

I need to confirm that I can use a 10K rated (most likely it will be a 22 or 24K, cause that's how most 3P panels come in the brands I use)

I am sure you are fine with 10k. Even if you were not, Note that considering you will likely be using a main breaker panel, Ill bet the main has a higher than 10k AIC and the branch breakers will series rate with it.
 

Fnewman

Senior Member
Location
Dublin, GA
Occupation
Sr. Electrical Engineering Manager at Larson Engineering
Not all transformers have primary taps. When they do, they are there for adjusting the secondary voltge(s) to a standard 120/240, 480/277, etc. when the utility voltage in the area of use is not nominal. Where the POCO voltage varies frequently, automatic tap changers are often employed. P.S. -
Correction- I agree with iwire!
 
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