Electric Service Upgrade 460/265 to 480/277 5

[ftutelo]

I am looking into upgrading the electrical service to a commercial building. The building is currently fed from a 460/265v 500kVA service, installed in 1971. The new service will be 480/277 750kVA. All the existing power panels within the building have a voltage rating of 460/265V. Must these panels be replaced with new panels rated at 480/277?

 

[skiier]

A 1% increase in your system voltage is hardly a concern. I bet your local inspection authority will agree. Why not ask them?
The increase in size of your service will not require you to upgrade your existing distribution panels. You are only changing the main service. If your existing main service is a switchgear type and is rated for the ampacity of the new service than you can probably run the new main service directly into the switchgear. If the switchgear is not rated than you will have to subfeed it from the new main service thru a fused disconnect. You don't to have to change everything. You can integrate your old service in with the new one. This is the cheapest and easiest way but how you spend your money is up to you.

 

[busbar]

A few things should be verified. If feeder and branch-circuit fuses and/or circuit breakers are labeled/listed for the higher voltage, with switchgear interrupting ratings adequate for the new transformer, that should be acceptable for the proposed work. Conductors should be rated a default 600V. Other transformers, light fixtures, motors and related components should be useable in the ranges listed in ANSI standard C84.1.

Above all, you need concurrence with the AHJ.

 

[advidana]

I'll bet that 460/265V is something the electrical contractor or local mfg rep labeled on the panelboard and switchgear. Which is not a standard ul or nema rating for panel broards or switchgear that I know of. Check with the manufacture part number with the mfg to see what the actual rating are and see if your local mfg rep can have the existing equipment re-labled or what you need to do to upgrade them.

 

[jbartos]

Comment: There used to be induction motors rated at 440VAC, 3-phase. The nonstandard 460V nominal system voltage would fit them correctly.
440V system voltage is very old dating back to about 1940 or so
Visit

http://www.groban.com/electric.htm

etc. for more info

 

[advidana]

I believe that motors are rated by nema to run at + or - 10%. I have been designing building electrical systems for 40 years design over 10 thousand building installations or more in that time using with 120/208 vac 3ph.

I have connected 230 v and 240 volts 3ph motors with no problem. The only failure was a old 1 ph refrigrator rated at 240 volts It' compressor did not want to run with 208 v 1 ph voltage. That was back in 1962 and the refrigerator was over 20 years old. we replaced the refrigerator. most new equipment is rated 208v thru 230v 3 ph except for non- U.S.A equipment.

 

[advidana]

yea I know we are concern wth 460/265 v. I would check the lighting toggle switches to see if they are rated 277 v. other than that I cannot think of any other problem, maybe some control transformers inside starter, etc.

 

[jbartos]

Comment: Please, notice how many manufacturers offered 440VAC motors at the following web:

http://search.netscape.com/ns/boomf...tinghouse%22&clickedItemURN=http%3A%2F%2F

http://www.nelsonmachinery.com%2Fmo...url=http://www.nelsonmachinery.com/motors.htm

e.g.
GE
Westinghouse
etc.

 

[jraef]

Distribution voltage and utilization voltage are 2 different values. Standard distribution voltage in the US for a 4 wire system (Over 240V) is now 480Y277V (some older distribution systems might still have 440V because it is too expensive to change all of the transformers). I know of no manufacturer of circuit breakers, switches or any kind of equipment that would rate their products for any less than those values, it just would not make any economic sense.

A 3 phase MOTOR that you hook up to that system will likely have a UTILIZATION voltage rating of 460V. This is the design voltage of the windings, and is slightly lower to accomodate any potential voltage drop through the conductors. Lighting loads, because they are typically smaller, are still rated 277V. I have never heard of a 265V rated ballast, and again it would make no sense for a manufacturer to make one. However, a 277V rated ballast would likely work just fine at 265V.

I agree with advidana that the label you see is probably some sort of a quirk from an inspector not truly knowing these issues and making some poor contractor apply this silliness to the panelboard before he would sign off on the job. I have seen it done before. Most good contractors already know that the local inspector is the final authority, right or wrong!

Motors designed outside of the US are sometimes "rerated" for use here by overstating the 415V +/- 20% design voltage as "440" because it still falls into 440 +10%. Most consumers do not realize the difference because we used to call it 440V years ago and many people still do. This is primarily what jbartos found above. My experiance is that these motors will have shorter lifespans and run hotter, especially when the distribution voltage climbs to 500V+ on occasion. If you tried to buy a new motor designed for the US market and wanted a true 440V nameplate rating, you would need to special order it.

"Venditori de oleum-vipera non vigere excordis populi"

 

[busbar]

jraef’s observations are well supported by chapter 3 in IEEE standard 141-1993, and Donald Beeman’s Industrial Power Systems Handbook, first published in 1955.

 

[jbartos]

Comment: A larger number of 440V, 3-phase motors are applied in shipboard applications where traditionally the power distribution voltage is 450V, 3-phase.
See IEEE Std 45

 

[ftutelo]

Thanks to all who responced to my question.
Today the utility opened the transformer enclosure, the secodary voltage of the transformer as per the name plate is 460/265v 3phase. This was the standard voltage provided by the utility when this transformer was installed in 1971. Since all the electrical distribution equipment in the facility is custom made the manufacture rated the panels to match the service. But, although the panel name plate shows the rated voltage at 460/265v the circuit breakers are all rated for 600v and there interupting rating is still adequate for the new service. So, as was suggested in several replies I will review this issue with the AHJ.

 

[jbartos]

Suggestion: The switch from 460V to 480V may affect 440V rated 3ph motors, beside other possible loads vulnerable to voltage increase. These should either be replaced or an autotransformer provided to decrease the coming 480V to 460V.

 

[busbar]

Any chance there is a 2½% tap or two that could be changed on the 460V-secondary transfomer? 480/460 = 1.043