Voltage variation question

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sparrott4

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Landscape lighting transformers transform house current to a range of voltages from 12 to 22V. Since there is no regulation circuitry, any variation above or below 120 V will cause a proportional rise or fall on the low voltage side. This can be critical since low voltage halogen lamps have a narrow acceptable voltage range (10.8 to 12.0V).

Does anyone have information on the ranges of house voltages likely to be found? Also, how much voltage drop could be expected during times of high energy use? Also, are voltage spikes common? How high can they go, and for how long?

Lastly, is there an inexpensive piece of equipment that can record voltage over a period of time?

Thanks.
 
iwire

iwire

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Location
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Re: Voltage variation question

Originally posted by sparrott4:
This can be critical since low voltage halogen lamps have a narrow acceptable voltage range (10.8 to 12.0V).
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I don't understand, halogen lamps are incandescent lamps and can be run from 0 volt up to their rating.

Running them under voltage only prolongs their life.
 
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bphgravity

Senior Member
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Florida
Re: Voltage variation question

I commonly find the range of voltage to be as low as 110 volt to as high as 130 volt. I purchase lamps with ratings from 120, 125 and 130 volts with no real concern of the connected voltage.
 
charlie

charlie

Senior Member
Location
Indianapolis
Re: Voltage variation question

Gregory is correct at the service point. Don't forget the additional voltage drop that is expected from the premises wiring system. The total voltage drop may be as much as 10%.

I also question why the additional voltage drop would be a problem with a resistive element? The lighting circuit will work albeit with a loss of lumen output. :D
 
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ken987

Senior Member
Re: Voltage variation question

Running them under voltage only prolongs their life.
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Oh no it don't

Halogen lamps life depends on the hot circulation of gas inside the lamp. The filament will give off some of its material as it burns, and with the high temps and circulation will redeposit this material on the filament. Running at a reduced voltage will hamper this and shorten the life. This is what I was taught at a Phillips lighting class I attended.

[ March 18, 2005, 08:25 PM: Message edited by: ken987 ]
 
charlie

charlie

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Location
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Re: Voltage variation question

Assuming you are correct, I have just learned something I didn't know. If that really happens, what keeps the filament material from depositing on the envelope or it depositing in an uneven fashion? It looks like there would be uneven places on the filament, it would develop hot spots, and burn out quickly. :D
 
charlie

charlie

Senior Member
Location
Indianapolis
Re: Voltage variation question

OK Tom, what keeps the filament material from depositing on the envelope or it depositing in an uneven fashion? :confused:
 
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ken987

Senior Member
Re: Voltage variation question

That's a good question. I know touching the lamp leaves a oilily residue that creates a hot spot, and instead of the filament material depositing back on the filament it builds up on the hot spot.
 
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sparrott4

Member
Re: Voltage variation question

While this is getting away from my original question, I do have good info from the engineers at Sylvania. They explain why there is a narrow voltage range for tungsten halogen lamps to operate efficienctly.

It has to do with the tungsten/halogen cycle. I explain it fully in my article on the subject at:

Why Voltage is Key for Tungsten Halogen Lamps.
 
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sparrott4

Member
Re: Voltage variation question

To finish up on my original question, I hear from you guys that ranges from 110 to 130V are not uncommon.

If an electrician finds a breaker panel where voltages seem to be unusually low or high, I assume that the problem could be traced either to:

1. Incorrect voltage coming from the municipal supply, or
2. A problem inside the house with the wiring or load

Given these options, could you suggest some basic troubleshooting and remedies for the electrican.

I want some knowledge to share with the landscaper so he can work with the electrican to identify and correct the problems.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Re: Voltage variation question

sparrott4 It is very common to use dimmers on tungsten halogen lamps, perhaps you are correct that the life is shortened by this though I still have my doubts.

Considering these lamps are often used with dimmers (dimmers that reduce the voltage) I would not even think about worrying about a low voltage condition at the fixture.

A high voltage condition I would look into.

Originally posted by sparrott4:
To finish up on my original question, I hear from you guys that ranges from 110 to 130V are not uncommon.
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UL requires electric equipment to operate safely + or - 10% of the rated voltage in the case of 120 volts this results in a range from 108 to 132 volts.

This range includes utility and premise system variations.

Originally posted by sparrott4:
If an electrician finds a breaker panel where voltages seem to be unusually low or high, I assume that the problem could be traced either to:

1. Incorrect voltage coming from the municipal supply, or

2. A problem inside the house with the wiring or load
Click to expand...
High voltage is almost always a utility issue, low voltage can be either utility or premise problems.

Originally posted by sparrott4:
Given these options, could you suggest some basic troubleshooting and remedies for the electrician.

I want some knowledge to share with the landscaper so he can work with the electrician to identify and correct the problems.
Click to expand...
I believe that question crosses the line this forum has about giving advice to those outside the trade.

I am not about to help a landscaper troubleshoot high or low voltage conditions. If a homeowner is experiencing high or low voltage conditions they should contact the utility or a qualified electrician.

Here in MA if you follow the state laws a landscaper can not install low voltage landscape lighting. A licensed electrician is required.

[ March 30, 2005, 04:22 PM: Message edited by: iwire ]
 
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