Dry type transformer

[packersbay]

Hello I am troubleshooting electrical issue with lighting on a commercial building. I am getting about 296v on the lighting circuit causing led fixtures to not function correctly as they are rated for 277v. I’ve check voltage at panel and still getting 296v. I’ve come down to Maybe issue with indoor dry type transformer. Any ideas on how I can fix this voltage issue?

 

[infinity]

What is the voltage of the system supplying the building? 480Y/277? If so then it could be a utility problem.

 

[packersbay]

Utility company verified there side and it’s all good

 

[infinity]

Utility company verified there side and it’s all good

So you have a step up transformer?

 

[packersbay]

Correct

 

[Tulsa Electrician]

Are getting 296phase to netural on on three legs? What is you phase to phase voltage on all three.
296*1.732 =512.67
You may need to re tap

 

[HEYDOG]

Correct

Are all three phases 296 volts to the grounded conductor?

 

[infinity]

What is the primary voltage and what are the three L-N voltages?

 

[packersbay]

Are all three phases 296 volts to the grounded conductor?

Yes that’s correct

 

[packersbay]

Are getting 296phase to netural on on three legs? What is you phase to phase voltage on all three.
296*1.732 =512.67
You may need to re tap

Yes getting 296v to neutral on all three legs

 

[Tulsa Electrician]

What are you getting line to line?
Also as others have mentioned.

What is the primary voltage and what are the three L-N voltages?

 

[Tulsa Electrician]

Also check your meter on another system to be sure your not having an issue there.

 

[packersbay]

What are you getting line to line?
Also as others have mentioned.

About 512v

 

[infinity]

Can you post a photo of the transformer nameplate so we can look at the taps?

 

[infinity]

About 512v

Primary voltage is the low voltage side.

 

[packersbay]

Can you post a photo of the transformer nameplate so we can look at the taps?

Yes I can tomorrow when I show up back on-site.

 

[infinity]

If the supply is a 208Y/120 volt system it sounds like your primary voltage is around 221 volts. Is the utility a 208Y/120 volt system?

 

[packersbay]

If the supply is a 208Y/120 volt system it sounds like your primary voltage is around 221 volts. Is the utility a 208Y/120 volt system?

Yes 208Y/120v

 

[Tulsa Electrician]

If the supply is a 208Y/120 volt system it sounds like your primary voltage is around 221 volts. Is the utility a 208Y/120 volt system?

Can you post a photo of the transformer nameplate so we can look at the taps?

In case you wondering how the math works.
With a ratio of 2.3
480/208=2.3
512/2.3= 222.6 primary voltage
If you want to do it the other way
208 to 480
208/480= .433
1/.433= 2.3

A pic of the tag will confirm your transformer set up. It will also give a list of taps which you can change to correct the output voltage if need be.
Look forward to what you find.

 

[LarryFine]

Is this a reversed step-down unit?