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Old 03-15-2008, 05:33 PM   #1
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Electronic Ballast?


Hi;
I have several fluorescent fixtures (2x40w T12, Diamond Plate) which I would like to control using a motion sensing switch.
Reading the specs on one particular switch, it cannot be used with fixtures that use an electronic ballast.
I'm trying to figure out whether my Diamond Plate (Lithonia Lighting) fixtures, and/or the other fixtures use electronic ballasts.
Is there an easy way to find out without taking the fixture apart? I cannot seem to find a spec sheet on the Diamond Plate lamps.

I assume that the motion sensing switches use triac driven outputs, and thus cannot control be used with an electronic ballast.

Thanks for any info

FW

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Old 03-15-2008, 06:20 PM   #2
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Electronic Ballast?


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The fixture should be easy to take apart. Generally one twisty clip thing.

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Old 03-15-2008, 11:59 PM   #3
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Electronic Ballast?


All magnetic ballasts that I've ever seen have a slight delay from when you hit the switch until the tubes actually light. If it's instant on, it's an electronic ballast. If it's not instant on, it could be either type. The reason is because each type works differently.

In a magnetic ballast circuit when power is applied, the ballast applies anywhere from 300 to 800 volts across the tube. At the same time it applies only a few volts (at several amps) across the two pins at each end of the tube. There's a little element at each end of the tube that gets red hot, and allows the high voltage to strike an arc inside the tube. Once the arc is established, the tube is basically short circuited, sort of like an arc welder but at much lower current. Once this occures, the ballasts power goes into this arc, and very little current flows across the elements at each end. Hence, the delay upon start-up.

An electronic ballast hits the tube with a similar voltage, but at a much higher frequency. At this high frequency, an arc can be established without heating the ends of the tube. These tubes are sometines called 'cold cathode'. Since there's no heating, the light comes on much quicker.

This is also why the tubes are generally not interchangeable, though there are exceptions.

Rob
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Old 03-16-2008, 11:02 AM   #4
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Electronic Ballast?


Motion detectors should operate any load provided it is in the amp range of the detector. Just like a regular light switch. However, I am not real familiar with motion detectors but I must take a guess that it operates similar to a photocell. Opens and closes the circuit. Constant triggering would not be beneficial to flourecents. Is there a gain adjustment?

Last edited by J. V.; 03-16-2008 at 11:09 AM.
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Old 03-16-2008, 12:52 PM   #5
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Electronic Ballast?


A photocell and a motion detector both do pretty much the same thing. Control a load. They both have internal circuitry that needs power to operate. How they get this power is where they differ.

Most photocells have 3 wires. A hot, a neutral, and a switch leg. The control power is derived from the hot and neutral.

A motion detector usually has only 2 wires. A hot, and a switch leg. No neutral. The reason being that some switch boxes don't have a neutral in them. It still needs control power. In this case it is derived by sending a very small amount of current through the load, and 'stealing' a bit of it. This works well provided there is an actual load in the circuit. An electronic ballast only becomes a load after line voltage is applied. Thus, the motion detectors internal circuitry will not stay charged up.

Most motion detectors have a minimum load requirement. Usually 25 watts or so. Another thing they won't work with is a fluorescent fixture that has a magnetic ballast and a starter. These are an older type, usually 24" or less.

They work fine with incandescent lights, small motors (fans), magnetic ballast fluorescent fixtures without starters, halogen lights, and most other stuff non-electronic.

Rob
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Old 03-17-2008, 06:26 PM   #6
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Electronic Ballast?


Thanks for the info;
I believe my fluorescent lamp has T12 bulbs, which I recognize as standard type.
The motion detector I was thinking of buying has a delayed off, so repetitive switching would not be a problem. The one I was looking at will keep the lights on for 20 minutes max. That seems about right for the efficiency of the fluorescent to be realized.
I don't like to have fluorescents being turned on and off frequently, but on the other hand, don't like the concept of leaving them on all day when they will be used only a few times during the day.

What I would like to do is figure out whether or not it is actually cost effective to purchase and install the motion detector switch.
The switch will cost about $18+ s/h, then I need to move the switch to a location where the motion would be properly sensed. It's a basement room, so wiring is not going to be an issue, only a little more time consuming than just changing a switch. I suppose I should try it in the original switch position before I re-wire to move the switch. Maybe the field of detection is wide enough to capture most movement in the room from the current switch location.

If I don't buy the motion detector, and allow the light to be switched on and off for shore periods, perhaps this will only reduce the life of the bulb/ballast by a small amount.
I do not believe I am wasting electricity when I turn the lights on and off, as I have never observed a surge current for fluorescents that compares with incandescents.
I could be wrong about this though. I should probably do some more reading.

FW
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Old 03-18-2008, 05:06 AM   #7
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If you have a neutral available, I would suggest buying a 3 wire motion detector. This will solve the problem of worrying about whether your lighting is electronically controlled or not.

The below 2 links point to Australian products. I'm sure similar products & product options are available in the USA. Also, these documents may enlighten you more about the installation requirements of 3 wire vs 2 wire motion detectors.

http://updates.clipsal.com/ClipsalOn...s/W0000496.pdf

http://updates.clipsal.com/ClipsalOn...s/W0000520.pdf
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Old 03-18-2008, 09:34 AM   #8
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Electronic Ballast?


Quote:
Originally Posted by elkangorito View Post
If you have a neutral available, I would suggest buying a 3 wire motion detector. This will solve the problem of worrying about whether your lighting is electronically controlled or not.

The below 2 links point to Australian products. I'm sure similar products & product options are available in the USA. Also, these documents may enlighten you more about the installation requirements of 3 wire vs 2 wire motion detectors.

http://updates.clipsal.com/ClipsalOn...s/W0000496.pdf

http://updates.clipsal.com/ClipsalOn...s/W0000520.pdf
Presently, there is no neutral in the switch box, but the wiring is readily accessible, and getting another cable into the box would not be a problem. I will probably have to move the switch anyway, so that the motion is detected properly.

FW
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Old 03-18-2008, 10:51 AM   #9
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Electronic Ballast?


Quote:
Originally Posted by fw2007 View Post
Presently, there is no neutral in the switch box, but the wiring is readily accessible, and getting another cable into the box would not be a problem. I will probably have to move the switch anyway, so that the motion is detected properly.
FW
FW, if I were in your shoes, I would be opting for a 3 wire setup. Obviously, this means installing a neutral conductor & this would therefore eliminate any problems with regard to "switching". If you don't wish to do this, you will have to explore the avenue of a "load correction device", bearing in mind that the device parameters need to be satisfied.
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Old 03-18-2008, 04:41 PM   #10
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Electronic Ballast?


I'm beginning to wonder whether I have opened up the proverbial can of worms here!
How much money am I going to save if I install the motion detector switch?
Will the cost of the installation be recouped by the savings in electricity?

Perhaps with a little 'education' of the users of this lighting, we can save the money without installing the switch.
After doing some research online (Wikipedia), I have learned that the average break-even point for on time of a fluorescent fixture is 20 minutes, meaning that if the lamp will not be used again before that time, it should be turned off when the person leaves the room.

Being that we pay a higher price per kwhr than the national average (I think we pay 0.12/kwhr), that time would be even shorter.

In any case, whatever I decide to do, I appreciate all the advice and info I have received here.

FW

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