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Old 03-25-2011, 02:56 PM   #1
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outside mercury vapor light


I have a mv-175w 702 light that I need help wireing, bought this light
and it blue the 175w bulb, got to checking it. takes 120 volt for light, but when checking where bulb goes it has 330volts. Can anyone help .
Thanks Koenton

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Old 03-25-2011, 04:12 PM   #2
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MV fixtures have a ballast that step up the voltage.

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Old 03-25-2011, 07:39 PM   #3
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I always thought that ballasts were to limit the current,
That would mean they lower the voltage,
after the lamp has started.
A high voltage is supplied by the igniter for a short period
to strike up the lamp.
Once the lamp has struck up,
then the ballast will limit the current.
as these lamps have a negitive temp coefficent.
That means that as they get hotter the impedance drops
that would allow more current to flow, so the lamp gets hotter.
This is called thermal runaway.
Thats what the ballast is there fore to prevent this.
To limit the current.
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Old 03-25-2011, 08:32 PM   #4
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Quote:
Originally Posted by dmxtothemax View Post
I always thought that ballasts were to limit the current,
That would mean they lower the voltage,
after the lamp has started.
A high voltage is supplied by the igniter for a short period
to strike up the lamp.
Once the lamp has struck up,
then the ballast will limit the current.
as these lamps have a negitive temp coefficent.
That means that as they get hotter the impedance drops
that would allow more current to flow, so the lamp gets hotter.
This is called thermal runaway.
Thats what the ballast is there fore to prevent this.
To limit the current.
That is exactly what happens with this ballast.

As the (here, mercury) lamp warms up, it will draw more current and the 330 volts measured with no lamp in the socket will drop as part of the current limiting process. I'm not sure what the final voltage is for this (175 watt) lamp.

Some mercury vapor lamp ballasts are a "straight coil" where the "high" strike voltage given to the lamp (to jump the gap between the two electrodes in the lamp) is dropped solely due to the increasing current draw of the lamp versus the constant impedance of the coil. (Volts across the coil equals amperes times impedance). Some ballasts, notably for high pressure sodium lamps, have a separate circuit as an "igniter" which produces a timed higher voltage pulse.

If the initial lamp voltage needs to be different from the supply voltage, the transformer secondary and the ballast can be the same coil.
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Last edited by AllanJ; 03-25-2011 at 08:51 PM.
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Old 03-25-2011, 10:37 PM   #5
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Thanks Very much
I bought this light off e-bay and installed it and it worked two times
then quit, checked out the switches, even bought one before I took
light down, make extion cord and pluged it up and that is how I found
out they it was getting 330 volts out, the bulb only lasted two times
after that it would not burn again, that is why I was checking the wires
and switches, it burnt the resister inside bulb into at one end. Thanks
again for info. it had me worried about the wireing.
Thanks again
Will in Al
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Old 03-26-2011, 02:29 AM   #6
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First thing first.,

Olé 175 W MV ballast open circuit voltage is about 250 volts any higher it will burn out the bulb and fully running the bulb voltage will drop down a little about 230 or so.

You will NOT able get the ballast for old MV units but you can still get replacement bulbs but it getting limited otherwise the other option is get a MH { Metal Halidé } or large compact flourscent both will throw out good amout of lights if used right.

I Do stock few HPS { High Pressure Soduim } or MH one of the two most common one I stock but I can get LCFL if the customer request it.

For MV they will have small restoir for starting probe to start up MV bulbs did you double check the ballast to see what wattage it rated some case you may have 250 watts verison by mistake.

The 250 watter will have higher open circuit voltage than the 175 watters will be but not a huge margan otherwise it may have MH probe start ballast in there { one warning with MH Bulbs make sure you get open rated bulbs otherwise get one with enclosed bottom luminire this is crictal on MH's }

If that the case please post the ballast number if you can see it then one of us { electricians } can able tell you the correct bulb and supply voltage as well due some of them do come in 240 volt supply verison as well.

Merci,
Marc
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Old 03-26-2011, 02:11 PM   #7
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I looked at the ballast and it had model N0:E-BAL-V017,HID BALLAST- OPEN CORE & COIL, 175W H39 MV,120 VAC 60HZ MAX 4.00A. I think that is the wright ballast for this light, don't you? I am going to get another bulb and try it again hope it was just a bad bulb. Thanks for getting back with me. I will let you all know what happens.
Thanks again for all the help
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Old 03-26-2011, 09:11 PM   #8
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How many lamps had a very short life?

H39 is the correct ballast type for 175 watt mercury vapor lamps and a 120 volt AC power supply.
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Old 03-26-2011, 10:20 PM   #9
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Thanks for reply, thought that was wright, do you think I just got bad bulb, the reason it blowed? I will try another one hoping it will last.
Thanks again for everyones help
Will in Al
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Old 03-27-2011, 09:00 AM   #10
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Unfortunately we cannot rule out a bad ballast.

You would need to find out what the open circuit (no load) voltage should be for the ballast. Then measure the voltage across the lamp as soon as you turn the light on, observe the pre-heat arc come on inside the bulb, and immediately switch it back off if the voltage is way too high.

The resistor is a mini-ballast for the preheat circuit which consists of a third electrode next to one of the other two electrodes in the lamp. The preheat is a (smaller) mercury arc that works the same way as the regular mercury arc that produces the light. If the resistor burns out then the lamp cannot start as the current can't jump the (longer) gap between the main electrodes when the lamp is cold.

Some of the time during preheating, the resistor will have nearly the full no-load voltage applied to the lamp applied across it so overvoltage from the main ballast could fry the resistor.

The main ballast is a coil rather than a resistor because a resistor will dissipate, or "waste", more energy as heat compared with a coil.
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Last edited by AllanJ; 03-27-2011 at 09:13 AM.
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Old 03-28-2011, 04:22 AM   #11
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I did double check with my chart I keep in my shop and the typical open circuit is 240 to 270 volts @ 120 volt supply { primary side }

so it is pretty much right on the spot however you may got some bad bulbs but try a diffrent namebrand bulb somecase it will clear up.


By the way the common Dusk to Dawn MV { Mercury Vapour } will use the HX ballast { reactor type } and you will see no capaitour at all. if you do see one there then you will have CWA ballast the OCV { open circuit voltage } will be little more higher.

So try diffrent bulb first before we can rule the ballast out.

If the ballast is toasted or shorted or other reason there will be no replacement ballast for Mercury Vapours at all.

Merci.
Marc
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Old 04-22-2011, 04:00 PM   #12
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Hello Alanj
Sorry for the long delay, on the light I needed help on I thought, the bulb burnt out, got another bulb and it is working fine now, hope that was all it was, but I only turn it on every once in a while, I have a shop about 100 yards from my house, I only use it when I have to go to shlp at night, I think they sent me rong bulb, got up with seller and sent the old bulb back and he told me that that was not the bulb that came with light, when I ordered the light I asked for clear bulb, and they sent clear one, but it was the right number on buld. Thanks for everyone help.
Will
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Old 04-23-2011, 01:23 AM   #13
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Just want to give you a head up the 175 W MV bulbs do come in both clear or coated verison the coated will have slightly better colour retation than clear bulb verison and the costwise it should be about the same.

The coated verison mean it have inside white coating to soften up the harshness and enchance { improve } the colour espcally with red and green that where it is weak on it. { they are very bright on bleu colour specturm }

Merci,
Marc
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Old 04-23-2011, 09:01 AM   #14
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Thanks for reply,
I always thought that the clear bulbs would give off more light than white ones, what does the bulbs usualy coast? You also said that you can't buy ballests for mercury vapor lights any more I have just bought this light, if the ballest goes out you saying I will have to through it away.
Thanks Will
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Old 04-23-2011, 12:02 PM   #15
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Quote:
Originally Posted by koenton View Post
Thanks for reply,
I always thought that the clear bulbs would give off more light than white ones, what does the bulbs usualy coast? You also said that you can't buy ballests for mercury vapor lights any more I have just bought this light, if the ballest goes out you saying I will have to through it away.
Thanks Will

The MV bulbs are pretty much old school it been in use senice late 30's or early 40's and still useing now.

The clear bulb may have slightly more brightness but not very much and it will have pretty strong bleu-whiteish light pattern

And unforetally that is true about the mercury vapour ballast they stop making them couple years back and if any MV ballast on shelf will be disappair pretty much by now so if you have to replace this luminaire or ballast there is other luminaire source you can use either Metal Halide { more brighter and more whiter in colour } or super compact flourscent { about right on the par with colour with Metal Halide or other flourscent bulbs colour you have in the house }
Or get HPS { High Pressure Soduim } but only quirk is it is yellowish colour but very bright

So therefore it is your choice what to do next

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