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Steve G.
Steve G., Electrical Engineer
Category: Electrical
Satisfied Customers: 16745
Experience:  27 years in Electrical Engineering, designing electrical plans and specifications.
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Steve I have some fans that are currently wired for 110v but

Resolved Question:

Steve I have some fans that are currently wired for 110v but can be rewired to run for 230 volt. Problem is I would really like to run them at 277v because the power to the building is 277/480 - 120/208 trying to conserve my amps instead of running off the 120. But I am a little confused on what the wiring difference because the 230 is the two hots but the 277 is one neutral and one hot. So would I rewire the fan to 230 run the neutral to ? and the hot to ? The motors amps are 1.7 at 110 and .77 at 230
Submitted: 1 year ago.
Category: Electrical
Expert:  Steve G. replied 1 year ago.

Hello there and welcome to Just Answer. My name is XXXXX XXXXX X will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

Now...in a typical commercial building, you are likely to find two voltage schemes: 480/277 three phase 4 wire and 120/208 three phase 4 wire. What does this mean?

In a three phase 4 wire system, you have three phase 'hots' and a neutral (we will disregard any grounds for this explanation but they are there of course). On a 480/277V system, the voltage between any of the two hots (phase wires) is 480V and the voltage between any of the hots and the neutral is 277V. This allows heavy HVAC equipment to use the 480V and lighting to use the 277V.

Similarly, on the 120/208V side of things, the voltage between any two 'hots' or phases is 208V and hot to neutral is 120V. In this case, we use 208 for smaller motors and quite often '230V' loads and of course 120V for receptacles.

In case you are wondering, the relationship between 277 and 480, and 120 and 208 is the square root of three. We use math everywhere in engineering :)

So, my advice would probably be to use 208V for your 230V fans rather than 277V which I think would be too high - of course check the manufacturer's literature to see if they will work on 277.

If they do, you would use a single pole breaker out of one of a 480V panel and run a neutral back to the neutral bar. That will give you 277V.

If you decide to go 208V, you would use a double pole breaker in your 208/120V panel and run two hots to the fans. No neutral.

I hope that makes sense. I'll be here if you need further help with this issue.

 

 

 

 

Please let me know.

Regards

Steve

Customer: replied 1 year ago.

Steve,


 


Excellent breakdown of the power issue . . . really helps. SO if I use the 277 single pole do I need to use the 230v wiring scheme or the 110v scheme on the fan. Currently wired for the 110v. Mfg says 277 should be fine.

Expert:  Steve G. replied 1 year ago.

If the manufacturer states that the fans will run on 277V (and not explode lol) then yes, you would set the fans to the 230V scheme and run them from a 15A or 20A single pole breaker in your 480/277V panel with a neutral back to the neutral bar. If the runs are not excessive, you can use #12 conductors.

Also, I read through your question and noticed that you were trying to 'save amps'. Be aware that no matter what voltage you run these fans at, they will use the same amount of power (watts). You will not save money - at least in utility charges by running them at a higher voltage. Watts are volts x amps. The fan has a wattage just like a light bulb and you get charged for watts, not volts or amps.

I'll be here if you need further help with this issue. Please let me know.

Regards

Steve

Customer: replied 1 year ago.

Thank you.

Expert:  Steve G. replied 1 year ago.

You are most welcome.

If you would, please rate my service today using the smiley faces or stars that appear right here. It is the only way I am compensated by this site and it works like an eBay or Amazon rating so please consider clicking on one of the better choices :)

I thank you in advance.

Regards

Steve

Steve G., Electrical Engineer
Category: Electrical
Satisfied Customers: 16745
Experience: 27 years in Electrical Engineering, designing electrical plans and specifications.
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