# Voltage drop at panel



## gunnut666 (Nov 24, 2011)

Hi
I've never looked for voltage drop at the panel, so I don't know if this is normal.
Connecting my multimeter to the busses of the 240V (meter pedestal) panel, I note that voltage slowly drops from 242V to about 238V as the metal halide fixtures warm up. The voltage almost instantly restores when the lights are turned off.
The only nonlighting load on this panel is the irrigation control panel.


Thanks


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## Hmacanada (Jan 16, 2014)

How large is the service?
4volt drop is nothing, depends how much load your adding at startup.
2 lights or 10?


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## gunnut666 (Nov 24, 2011)

I believe it is a 200A service.
There are 16 fixtures, 2 x tennis courts and a playground.
Customer complains that the ancient fixtures seem to require a lot of service.
I asked for service history, but got none.
These tennis courts require rental equipment to change the 1000W MH ballasts.
I suggested that this cost created an illusion of premature failures.
I was checking for voltage fluctuations to appease customer.


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## Hmacanada (Jan 16, 2014)

gunnut666 said:


> I believe it is a 200A service. There are 16 fixtures, 2 x tennis courts and a playground. Customer complains that the ancient fixtures seem to require a lot of service. I asked for service history, but got none. These tennis courts require rental equipment to change the 1000W MH ballasts. I suggested that this cost created an illusion of premature failures. I was checking for voltage fluctuations to appease customer.


I think as long as the load is balanced on lines as close as possible 4 volts isn't hurting anything.
Are they all starting at one time?


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## LGLS (Nov 10, 2007)

gunnut666 said:


> Customer complains that the ancient fixtures seem to require a lot of service.


 Maybe they're so old they've outlived their usefulness.


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## Vintage Sounds (Oct 23, 2009)

Are these ballasts in the fixture head itself? They might be getting cooked by the lamp's heat. 

Based on your numbers you're only experiencing 0.4% VD. That can't be the problem.


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## minichopper6hp (Apr 19, 2014)

Rental equip? How high are they? We use a 21 ft little giant ladder to service all our tennis coirt lights.

Sent from my LGMS769 using Tapatalk


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## Chrisibew440 (Sep 13, 2013)

Anytime you apply load you get voltage drop. We try to compensate with conductor sizing.


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## gunnut666 (Nov 24, 2011)

Replies to several suggestions:
Once again, the voltage drop is at the panel buss, not at the fixtures.
The fix's _are_ all starting at the same time. I was only able to clamp my meter on one of the feed wires between the meter socket and the main breaker: 35A.
240V fix's on 2-pole breakers. Pretty well balanced.
Illegally standing on the top step of a 16' folding ladder, I can barely relamp. Sissor lift is required to reballast.


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## Chrisibew440 (Sep 13, 2013)

If all your fixtures are starting at once your gonna have voltage drop.


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## Rollie73 (Sep 19, 2010)

The voltage drop doesn't sound alarming at all. 4% drop is normal with that kind of start up load.

Sell the customer on new lighting....maybe some LED's


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## gunnut666 (Nov 24, 2011)

Thanks for all the replies.
The problems at this location are probably imaginary, but the property manager involved is generally a good customer.


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## hardworkingstiff (Jan 22, 2007)

gunnut666 said:


> Thanks for all the replies.
> The problems at this location are probably imaginary, but the property manager involved is generally a good customer.


A properly formatted (showing cost savings and pay back time) lighting replacement might be easily sold to the bean counters.


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## hardworkingstiff (Jan 22, 2007)

Vintage Sounds said:


> Based on your numbers you're only experiencing 0.4% VD. That can't be the problem.


0.4%? 

Voltage starts at 242 and goes to 238, 4-volt drop.

4/242 = 1.65%


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## Vintage Sounds (Oct 23, 2009)

hardworkingstiff said:


> 0.4%? Voltage starts at 242 and goes to 238, 4-volt drop. 4/242 = 1.65%


 Sorry, brain fart. Not sure how I got that at the time.


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## wildleg (Apr 12, 2009)

not trying to nitpick, but wouldn't the proper term for that be voltage sag, since he is measuring at the source (more or less) ?

voltage drop to me generally means the voltage drop between a source and a point down the line (like the difference between the source voltage and the voltage at the lights to me would be the voltage drop)


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## Big John (May 23, 2010)

There's voltage drop at every point in a circuit. You'd measure voltage drop even if you were right on the secondaries of the transformer. How much you see at the panel depends on size of the load, size of the conductors, size of the generator/transformer.

4 volts doesn't worry me. But I don't see where the 35A came from if you've got 16,000W of lights?


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## Chrisibew440 (Sep 13, 2013)

wildleg said:


> not trying to nitpick, but wouldn't the proper term for that be voltage sag, since he is measuring at the source (more or less) ?
> 
> voltage drop to me generally means the voltage drop between a source and a point down the line (like the difference between the source voltage and the voltage at the lights to me would be the voltage drop)


What would it be called, the panels being fed from another source being the transformer. Now I'm getting nitpicky.


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