# Question on VD



## ohiosparky99 (Nov 12, 2009)

457 at the main is to low, have them come out and check taps at the transformer


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## Mich drew (Mar 3, 2013)

Could it be because it is 108 there and everybody is running their A.C.s
24/7 causing a drop on the grid?


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## Surge03 (Sep 23, 2012)

Mich drew said:


> Could it be because it is 108 there and everybody is running their A.C.s 24/7 causing a drop on the grid?


I know its because there's a high demand for power because its hot, but this is a school with 3000 kids. But also we have a another school just as big and the lowest voltage I ever get is 470.


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## RIVETER (Sep 26, 2009)

Surge03 said:


> Currently on a job in southern CA and it's around 108 degrees out here. It's a High School with realy low voltage drop, getting 457 phase to phase at the main and as you know the further I go its average 443 phase to phase and secondary's are around 192 phase to phase. Locking out A/C units left and right, I know the code is 5% on the main which is 456volts, does this mean I'm **** out of luck to call the utility company? Would appreciate any suggestions, thanks. We have a 3 phase 277/480 volt 3K amp service.


Utility problem


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## Surge03 (Sep 23, 2012)

RIVETER said:


> Utility problem


But will they do anything about it? I have dealt with them before last year and all I get is anything above 456 is good and what ever downstream is my problem.


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## Jlarson (Jun 28, 2009)

I don't see a problem here, the VD limits in the NEC are not actually enforceable, they are just recommendations. You job specs may have a say but otherwise all the voltages you listed are within spec.


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## Surge03 (Sep 23, 2012)

Jlarson said:


> I don't see a problem here, the VD limits in the NEC are not actually enforceable, they are just recommendations. You job specs may have a say but otherwise all the voltages you listed are within spec.


On the main is within spec but everywhere else is 442 on primary's and 191 on the secondary's . Only other thing I can do is re tap all my transformers.


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## hardworkingstiff (Jan 22, 2007)

Surge03 said:


> Only other thing I can do is re tap all my transformers.


Be careful with that solution because during low demand the utility voltage should come back up which will make your re tap put out a higher voltage.

Around here, the utility is allowed a +/- 5%. So you can get a 10% swing. Sucks, but that's the way it is.


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## ampman (Apr 2, 2009)

Most a/c equipment has a minimum and maximum voltage the unit can use 443 does not sound to low for some equipment I would check the nameplate on each a/c unit first then go from there









Credit for this goes to the chuck Norris of electricity


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## Surge03 (Sep 23, 2012)

ampman said:


> Most a/c equipment has a minimum and maximum voltage the unit can use 443 does not sound to low for some equipment I would check the nameplate on each a/c unit first then go from there Credit for this goes to the chuck Norris of electricity


Thanks guys, this helps.


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## DriveGuru (Jul 29, 2012)

If you've got that much voltage drop at the end to equipment, and not measuring a drop in the main supply, you either have bad connections somewhere, or are using undersized wire. I would recommend calling a local electrical contractor(check for local EASA shops), preferably one that owns an infrared camera and can do thermography.


Sent from my iPad using electriciantalk.com


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## seelite (Aug 24, 2009)

You guys confuse the xxxx outa me. Started my apprentice in 1952 and voltage drop was always known as 'IR drop' while VD was what yoose call STD. I know english was a 2nd lanquage 4 me, but been communicating in eng. since 1940. Y u gotta confuse this senile citizen ? However, I must concede that the posts that I see in this forum indicate a higher level of training than what I saw in the post WWII yrs. - work safe!


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