overvoltage

[nakulak]

was doing a mall store recently and noticed the 480 was around 510. I was just there helping finish up, so I didn't mess with any of the trannies (the 208 was a little high). At what point do you feel responsible to start fiddling with the taps ? 10% ?

 

[iwire]

was doing a mall store recently and noticed the 480 was around 510. I was just there helping finish up, so I didn't mess with any of the trannies (the 208 was a little high). At what point do you feel responsible to start fiddling with the taps ? 10% ?

Almost never.

 

[brian john]

About the only time I have adjusted taps (Manual Taps) is when transformers with taps set for 480 VAC were installed in building utilizing 465 VAC.

 

[cadpoint]

About the only time I have adjusted taps (Manual Taps) is when transformers with taps set for 480 VAC were installed in building utilizing 465 VAC.

What piece or general types of equipment call for that size of service ?

 

[Electric-Light]

was doing a mall store recently and noticed the 480 was around 510. I was just there helping finish up, so I didn't mess with any of the trannies (the 208 was a little high). At what point do you feel responsible to start fiddling with the taps ? 10% ?

Motors don't mind 10% higher voltage, but no load loss in transformer goes up and magnetic ballasted fluorescent and HIDs operate at increased power leading to increased power consumption. Simple HX reactor type HIDs are affected substantially by line voltage, so +10% will substantially increase power consumption of parking lot lights operating on 480 or 277.

If you're reading +10% with heavily loaded transformer and its consistently high, then you might consider changing taps. If output at 208Y/120v is +10% consistently, 120v light bulbs will fail at 25-50% of rated life.

Office equipment uses switching power supply and they're not really affected by +10% voltage.

 

[kwired]

Might want to make sure POCO is not having voltage regulator problem before changing anything. If they are they eventually will discover it and will correct it and then your tap changes will be wrong again.

May also want to make sure any changes are based on the voltage when load is at a somewhat average level and not when it is at a high or low peak.

 

[brian john]

What piece or general types of equipment call for that size of service ?

In Washington DC, PEPCO delivers 480 VAC, in the burbs commercial services are delivered at 465 VAC.

In addition during the summer high peak periods in the outer limits of the service area we have measured 432 VAC, with transformers tapped for 480 VAC output voltage is low.

 

[kwired]

In Washington DC, PEPCO delivers 480 VAC, in the burbs commercial services are delivered at 465 VAC.

In addition during the summer high peak periods in the outer limits of the service area we have measured 432 VAC, with transformers tapped for 480 VAC output voltage is low.

Is 465 the target they want to achieve and why?

Around here pretty much all 480 services will measure around 500 with little or no load, 208 volt services will usually read about 215, 240 volt services will usually be around 250 with little or no load. Sometimes in cities or towns if multiple services are fed from one transformer you will see lower voltages, but not clear down to 432 at service equipment on a 480 volt system.

 

[ohmhead]

Votage ups & downs

Votage ups & downs

This week we finished up a project testing & start ups new construction CEP plant service 4160 v with no load 4335 volts power company ok were ok its what you get this will drop when loaded how much ill let ya know when we load it up this week . My home service iam the only one on my street with my own transformer completely by myself 400 amp service to my home single phase 120/240 v with load on 126 volts / 250 volts everyday never changes .

 

[Cow]

was doing a mall store recently and noticed the 480 was around 510. I was just there helping finish up, so I didn't mess with any of the trannies (the 208 was a little high). At what point do you feel responsible to start fiddling with the taps ? 10% ?

I'd call the power co. 510 is high...

I had to call the poco once when installing a Yaskawa drive, I think the drive could only handle less than 500 volts and I was measuring around 505.

 

[brian john]

Is 465 the target they want to achieve and why?

Around here pretty much all 480 services will measure around 500 with little or no load, 208 volt services will usually read about 215, 240 volt services will usually be around 250 with little or no load. Sometimes in cities or towns if multiple services are fed from one transformer you will see lower voltages, but not clear down to 432 at service equipment on a 480 volt system.

I have no knowledge of why they split their delivered voltage like they do and many contractors that primarily do work in the city get stung occasionally. Not that changing the taps is all that big a deal.