Hi, all. This is off-topic, but need some advice. I have a low-voltage lighting transformer for outdoor lights. It is rated at 200 watts max. I have lost the instructions and can't find info on the web. Is there any harm in only connecting 100 watts of lights to it? I seem to remember that the instructions said something about it not being recommended and to try to stay close to the max rating without going over. Mark from Kalamazoo

Hi

Not a problem. You can use any load less than a transformer rating. Do not exceed 200 watts.

Norm

:Hi, all. This is off-topic, but need some advice. I have a low-voltage lighting transformer for outdoor lights. It is rated at 200 watts max. I have lost the instructions and can't find info on the web. Is there any harm in only connecting 100 watts of lights to it? I seem to remember that the instructions said something about it not being recommended and to try to stay close to the max rating without going over. Mark from Kalamazoo
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I seem to recall doing some experimenting some time ago and finding that the lower the load (wattage) the higher the output voltage was on the transformer. You might want to check the output voltage, if it runs too high it might shorten the bulb life. I was testing an inexpensive knock-off one manufactured in China.

Richard

:Hi, all. This is off-topic, but need some advice. I have a low-voltage lighting transformer for outdoor lights. It is rated at 200 watts max. I have lost the instructions and can't find info on the web. Is there any harm in only connecting 100 watts of lights to it? I seem to remember that the instructions said something about it not being recommended and to try to stay close to the max rating without going over. Mark from Kalamazoo
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Thank you Norm and Richard. I couldn't think of a reason why it might be damaging to the transformer, but I did wonder if it might send too much current to the bulbs if there was less of a load on it. I will check it before and after to see if it makes much of a difference in voltage. Mark from Kalamazoo

A transformer run at lower than its rated load will produce slightly higher than rated voltage. That could reduce the life of the lamps somewhat. Measure the voltage with a voltmeter. Google "transformer regulation."

It should not damage the xfmr.

:A transformer run at lower than its rated load will produce slightly higher than rated voltage. That could reduce the life of the lamps somewhat. Measure the voltage with a voltmeter. Google "transformer regulation."
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:It should not damage the xfmr.

Hey...hey....hey:
I remember reading about that when I bought my 12 Volt yard lights. The thing about keeping the transformer loaded heavily was to keep the Voltage down so the bulbs would last longer. It seems that they had complaints from people about shoty bulb life, so they suggested loading the transformer down to keep the Voltage lower.
Lewis

If high voltage is a problem add some resistance in the line. Reducing lamps to 11 volts should increase bulb life many times.

Norm

::A transformer run at lower than its rated load will produce slightly higher than rated voltage. That could reduce the life of the lamps somewhat. Measure the voltage with a voltmeter. Google "transformer regulation."
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::It should not damage the xfmr.
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:Hey...hey....hey:
:I remember reading about that when I bought my 12 Volt yard lights. The thing about keeping the transformer loaded heavily was to keep the Voltage down so the bulbs would last longer. It seems that they had complaints from people about shoty bulb life, so they suggested loading the transformer down to keep the Voltage lower.
:Lewis
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:If high voltage is a problem add some resistance in the line. Reducing lamps to 11 volts should increase bulb life many times. Norm
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The cheap low voltage units don't have a regulator circuit. If you want to have better control, you can add a voltage regulator chip from Radio Shack and adjust the voltage to 11 volts regardless of the load. John

John: Can you tell me more about how to do this? I'm curious. Mark from Kalamazoo

:John: Can you tell me more about how to do this? I'm curious. Mark from Kalamazoo

Regulator chips work very well, but they are for DC, and not the AC used in yard lights. The famous 317 chip can give about any Voltage up to the recitfied output of the transformer, and with a simple pot circuit be made variable from about 2 to 12 Volts, and with a couple of outboard 2N3055 transistors, make a neat little variable power supply. There are any number of circuits all over the internet for this.

Lewis
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I have four 11watt bulbs on an 80watt AC Malibu transformer.

So the load was 50% or so. I got tired of replacing the bulbs... so I looked for a solution.

I first simply put a full wave bridge rectifier on it and the bulbs seemed to last for ever. I later added a filter cap and measured it at 12-13 volts DC.

So as a result of that positive experiment I decided to make a nice little regulated 12volt DC supply.

But it turned out cheaper to buy one. I found a great 12volt @ 12amp (switching-type) DC power supply online for only $20
"Mean Well s-150-12"

That's on a timer set for dusk-dawn now for about 5 years without so much an a single bulb failure!

Here it is now on Ebay for $20:
http://www.ebay.com/itm/Mean-Well-S-150-12-12VDC-12-5A-Power-Supply-/140804907574?pt=LH_DefaultDomain_0&hash=item20c8a06236

Thanks, Lewis and Peter. Yes, I forgot that you would have to be converting AC to DC for a regulated supply, but from Peter's experience, that works well.

Swapping the power supply for one that produces a lower voltage is a pretty simple solution.

:Thanks, Lewis and Peter. Yes, I forgot that you would have to be converting AC to DC for a regulated supply, but from Peter's experience, that works well.
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:Swapping the power supply for one that produces a lower voltage is a pretty simple solution.
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:John: The light I am operating has two 50 watt halogen bulbs. The only low voltage transformers I have seen are 88 watts and 200 watts. So, I went ahead and disconnected the backyard lights from the transformer and have been operating just the front light. Voltage went up from 11.75 to 12.1. I'll see how long this works. The bulbs are about 3 years old, so they may be nearing the end anyway. Mark from Kalamazoo