Is 480v more "efficient" than 208v?

[donw]

A 75kVA 480-208Y/120V Xfmr will have approx. 143W of losses. So, if you have more then 9 motors ( 9 x 17.3W = 155W) for each 75kVA transformer your installation would pay for itself by going to 480V instead of using just 208V. Increased light fixtures on a circuits, plus lower overall heat, would reduce cooling some.

I don't get that statement. The SES would be at 208v, so transformer losses are on the power company's tab.

 

[kingpb]

I don't get that statement. The SES would be at 208v, so transformer losses are on the power company's tab.

The comparison is 480 Volt service versus 208V service. If you have a 480V service, you will still need 208Y/120V for the loads that cannot be powered by the 480V. Those transformers losses (480-208Y/120V) would be on the facility side.

The losses for the 480V or 208V service transformers were not included in my quick analysis.

BTW: The utility company doesn't pay for anything. The losses in the service entrance transformers are built into the Owner's rate structure.

 

[hmspe]

I just needed some energy cost estimate to give to the owner, because an electrician was telling her how much more energy would cost at 208v than 480v.

It's amazing what some people will believe.

Here's another monkey wrench. SRP said they could provide a second 480v service in addition to the current 208v transformer...for a fee. That would dispense with the extra 208v transformer/heat problems, but up front costs are likely high and monthly meter costs of another service would outweigh any energy savings.

I've done this (Mesa First Assembly on Lindsay). This is another application where the the specifics of the job made it make sense. It's a large building, so it made sense to have the AC at 480; however, there is also a tremendous amount of theatrical lighting. We traded an additional meter charge against the costs of a couple of 500KVA transformers that can handle the third harmonics from the dimmers. Works well in this case, but I wouldn't recommend it as a matter of course.

And then there's the cost of redesign...and some of the A/Cs have already been purchased. I think I have her convinced to keep the design as it is.

A/Cs on order makes the decision easy.

Martin

 

[jimioy]

donw - definitely go 480/277, Sq D, Digital building controls, UPS and generator backup, and I think the prices are getting better for lighting controls.