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Discussion Starter · #1 ·
I have a 20-40 year old Mercury Vapor light fixture in my yard above the stairs that lead up to my house. It was non-functioning when I moved in. If I had to guess, based on it's appearance I would say that it is a 175Watt fixture.

I can hear that the dusk to dawn feature is still working. (It makes a vibrating sound for about 2 minutes every dusk/dawn, followed by a "CLICK" sound)

I am assuming that the bulb is burned out, but I suppose the ballast could be fried also.

I am very frugal with energy. My monthly electric bill runs about $60 (or less) a month. I am not willing to waste 175W, 100W, or even 65W for a light that stays on all night, but at the same time, I need a LITTLE light out there to illuminate the stairs leading up to my house. I have been using a series of battery operated LED motion detector lights, dispersed at intervals along the stairways/path leading up to my hillside house, but these run out of batteries every few months, and don't really put out a lot of light.

I have calculated that it would actually be CHEAPER to operate a GE 14Watt CFL Outdoor Bug Bulb (with 60W incandescent light equivalent) from dusk to dawn than it would be to keep changing the batteries in the LED motion lights. It would also be more convenient and safer to have a light on all night.

Unfortunately the area light fixture in my yard is pretty high up, and difficult to reach without death-defying effort using my ladder that is not tall enough. I can however buy a bulb changing tool and an extension pole to replace the bulb without killing myself, but opening the top of the unit to rewire the socket directly to the dusk/dawn sensor, bypassing the ballast would be very difficult to accomplish.

SO, here are my questions:

#1: Can I install a self-ballasted 14 watt bulb into a 175 watt, ballasted Mogul socket, and expect it to work? (using a mogul to medium socket adapter) The ballast merely LIMITS the wattage from EXCEEDING 175 watts, correct?

#2: Worst case scenario is that the ballast is fried. If this is the case, what is the likelihood that it is still passing power to the socket?
 

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The old mercury vapor lamp ballast may or may not pass at 14 watts a voltage within tolerances taht the CFL will operate on.

At full brightness, the mercury lamp is actually running at a lower voltage when drawing its 175 watts.
 

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Discussion Starter · #4 ·
Why would the voltage change? Is that how the ballast limits the wattage? By reducing the voltage when the wattage tries to exceed 175watts?

Would that still apply if the wattage does not exceed 175?
 

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A ballast is basically a transformer which either steps up or down voltage and current. You would be putting 2 in series if you tried doing what you suggest so there for your voltage and current would be wrong.
 

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Discussion Starter · #6 ·
A ballast is basically a transformer which either steps up or down voltage and current. You would be putting 2 in series if you tried doing what you suggest so there for your voltage and current would be wrong.
This still doesn't make sense to me. I am trying to understand the science here.

A ballast is basically a self-adjusting transformer, that variably steps down the voltage to produce a specific wattage, correct?

In the case of a 175Watt bulb, the job of the ballast would be to make sure that the bulb ONLY receives 175Watts in order for it to function properly, agreed?

An unballasted 175Watt bulb will actually try to pull as much amperage as it can, until it burns out, thus requiring the NEED for the ballast.

If we use the formula: Watts = Amps * Volts, we get 175 = Amps * Volts, we could change the volts to respond to the amps which would be variable, in order to obtain our goal of 175 watts.

Therefore, if the bulb tried to pull 3 amps, the ballast would step down the Volts to 58.3, in order to achieve 175 watts, correct?

SO, this also means that if the bulb only tries to pull 1.46 amps, exactly 120 volts would be required in order to achieve 175 Watts, correct?

Thus, if the amps fell BELOW this threshold of 1.46 the ballast would do NOTHING, correct? The ballast wouldn't be configured to automatically reverse itself in order to STEP UP the Voltage above 120 Volts, correct?

If all this is correct, it should therefore stand to reason that a 14 watt SELF-BALLASTING bulb would only pull .14 amps (at 120 Volts), well below the threshold required to engage the ballast.

Does this make sense or am I crazy?
 

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Would that CF bulb even fit in there? Don't M-V bulbs have a fatter base? Maybe I'm thinking of something else, but I thought they made the screw-in part a different size so you don't go putting the wrong bulbs in the wrong fixtures.
 

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Discussion Starter · #9 ·
@hyunelan2
As I indicated, I would be using a socket adapter to make a standard bulb fit in a mogul socket. They are available at any hardware store (or on Amazon) for a couple of dollars.

@Scuba_DaveThe CFL bulbs that are designed to replace standard MV bulbs, and fit in mogul sockets are usually unballasted, designed to work with the existing ballast.

Due to the location of the lamp fixture, removing the ballast is not an option unless I also want to purchase a $300-$400 ladder. (See images below)

Unfortunately I am confined to a very tight budget to try to get this light working.


 

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Discussion Starter · #11 ·

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With any type of bulb that uses a gas vapor it takes a high starting voltage to ignite the gas. Also with any transformer there is no physical connection between the primary wires and the secondary wires, therefore you would not have the correct line voltage to fire your CFL bulb.
 

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Yeah, that's a tough spot
I think I'd be inclined to install a new fixture lower, just above that little junction cover
Would make it much easier to change bulks
While CFL's are supposed to last a long time...I find when installed outside they only last 2-3 years depending upon use & weather exposure
 

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Discussion Starter · #15 ·
Yeah, that's a tough spot
I think I'd be inclined to install a new fixture lower, just above that little junction cover
Would make it much easier to change bulks
While CFL's are supposed to last a long time...I find when installed outside they only last 2-3 years depending upon use & weather exposure
Thanks Scuba_Dave!

I was thinking exactly the same thing. Not only would a lower location make it make it easier to change bulbs (or remove ballasts), if I am going to replace a 175W bulb with a 14W bulb, it is not going to throw light nearly as far, and thus SHOULD be closer to the ground. Right at the junction box seems like the perfect height to get the stairs and a decent section of the hill below. (I still plan to use motion sensor lights at the bottom of the hill)

So, I guess my focus needs to shift to how to remove the existing fixture, instead of trying to remove the ballast from it. This actually looks like it will be an easier task than the latter, although STILL not possible with my existing ladder.

Hmm, maybe I can rent a ladder...

Once I get the fixture down, I can crack it open and see how easy it would be to bypass the ballast, then remount it right above the junction where it protrudes from the wall, eliminating the extension pole altogether.

And if that doesn't work, I suppose it wouldn't be that expensive to just replace the whole thing. (once I get past the ladder issue) Frankly, the existing fixture is kind of ugly anyway. Although, unfortunately all of the less expensive area lights I have seen are just as ugly as this one! It kind of defeats the purpose of my plan to save $60 a year in electricity if I have to pay $200 for the light fixture and its installation!
 

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I bought some CFL floodlight fixtures at HD
They were $20 - $15 rebate at the time..a steal...a few years ago
Anyway = they use 65w & are supposed to be equiv to 500w
They throw a lot of light

My HD has a variety of outdoor CFL fixtures & bulbs on sale
Might want to check it out
 

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Discussion Starter · #17 · (Edited)
I bought some CFL floodlight fixtures at HD
They were $20 - $15 rebate at the time..a steal...a few years ago
Anyway = they use 65w & are supposed to be equiv to 500w
They throw a lot of light

My HD has a variety of outdoor CFL fixtures & bulbs on sale
Might want to check it out
Frankly, I don't WANT a lot of light out there, on all the time, attracting bugs, etc. Spoils the ambiance. Initially, I was going to go with a 3W LED "floodlight", but I decided that's just not enough light for the intended purpose (illuminating the stairs just barely enough to be seen in the dark). The 14W CFL Bug Light seems like it will provide just the right amount of light to be able to see the stairs in the dark without a flashlight.

Does your 65W fixture use a fixed ballast, or can you put in self-ballasted bulbs of your choice?
 

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You could rent the size ladder you needed instead of buying.
 
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Frankly, I don't WANT a lot of light out there, on all the time, attracting bugs, etc. Spoils the ambiance. Initially, I was going to go with a 3W LED "floodlight", but I decided that's just not enough light for the intended purpose (illuminating the stairs just barely enough to be seen in the dark). The 14W CFL Bug Light seems like it will provide just the right amount of light to be able to see the stairs in the dark without a flashlight.

Does your 65W fixture use a fixed ballast, or can you put in self-ballasted bulbs of your choice?
The fixture takes any bulb....as far as I know...I can go check
It comes with a 65w CFL bulb w/ballast
You have conduit...maybe run another hot switch for a lower wattage light ?

I also had a motion detector that had a dual brightness setting
It would go down to 10% power (7w for a 75w incandescent)
Then go up to full brightness when motion detected
That might not work if you have trees/branches that would cause the motion sensor to go off
 
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