mathan1987
Member
- Location
- Seattle
- Occupation
- Electrical design engineer
What are the factors to consider when choosing the voltage of the power distribution system 208V/ 480V?
Voltage 208V/ 480V ?
- Thread starter mathan1987
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
As often as not the choice is made for you by the utility. They have rules about such things.
Well, do you need 120V circuits? If so, you'll be putting in a 208V transformer if all you have is 480.
Do you want to do 277V lighting because you have a lot of lighting load? You'd want 480V for that.
Do you have large motors (e.g. 480V is all they will take) or a large overall power requirement? Would you rather have smaller circuits and services (amp rating) to deal with that, or go with larger 208V distribution. At some point, the 208V service would just be too large and you'd need to jump up to 480 or higher.
Do you want to do 277V lighting because you have a lot of lighting load? You'd want 480V for that.
Do you have large motors (e.g. 480V is all they will take) or a large overall power requirement? Would you rather have smaller circuits and services (amp rating) to deal with that, or go with larger 208V distribution. At some point, the 208V service would just be too large and you'd need to jump up to 480 or higher.
The plant I was responsible for was supplied by medium voltage from the utility so we were free to choose our secondary voltage(s). Perhaps that is the situation for the OP?
Our shop utilized 480/277. 480 for machine tools, 277 for lighting.
208/120 supplied the office. 208 for HVAC and data center, 120 for office lighting and general purpose.
Our shop utilized 480/277. 480 for machine tools, 277 for lighting.
208/120 supplied the office. 208 for HVAC and data center, 120 for office lighting and general purpose.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Another consideration is the amount of load. For a commercial building if the load isn't too great then using 480Y/277 system and step down transformers may be more expensive than a simple 208Y/120 volt system.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Theoretically speaking, higher voltage is cheaper, because insulation is cheaper than conductor.
But, some higher-voltage equipment costs more, so that can offset the saving in wire costs.
It generally makes sense to receive the higher voltage when you have loads of both voltages.
Also, the relative amount of load of each voltage matters. It's best to price doing it both ways.
But, some higher-voltage equipment costs more, so that can offset the saving in wire costs.
It generally makes sense to receive the higher voltage when you have loads of both voltages.
Also, the relative amount of load of each voltage matters. It's best to price doing it both ways.
We have a double-ended feed here. One is from the utility and the other is a redundant backup from on-site generation. They are medium voltage.
There is a limit as to the economic feasibility of operating at a certain voltage. For the same amount of power transferred on a circuit, large current is handled if low voltage systems are chosen than if they are operated at higher voltages. That said, use lower voltages for safety or choose higher voltage to clip on costs of electrical distribution materials (high currents requires larger wires).
That’s correct. We had some high (>1000) HP and heat treatment systems that ran on MV directly. I didn’t mention that originally because it didn’t seem relevant to the OP.
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