Hi there to all memebers.
Im new to the lighting gallery and I had no idea their was a community of people with the same interest in electric lighting  like myself.

Anyways I am from London Ontario Canada and have a fiew questions.

My fave type of HID fixture is the outdoor dusk to dawn "bucket" light in a 100w Mercury vapor configuration with a dim  greenish worn out bulb so to speak. Very hard to come by!

I currently have a mid 90's Thomas &Betts 175 mv bucket light  that I converted to a 50w hps  (phillips ballast) when the original  175w MV  ballast started to buzz and eventually quit.

Being a fan of the dimmer old mercury fixtures I was not happy with the overly bright orange/yellow light output of the hps bulb.  After doing some reserch and browsing this fourm and youtube I have concluded that you can mix and match various types of HID bulbs and ballasts. So I got the ladder out and installed a clear 175w MV bulb in my converted bucket light with the 50w  hps ballast just to see what would happen, to my surprise it struck an arc and will light the bulb to what appears to be half  lumination. It hs been running all night long for several,weeks now and appears to have no issues. So after this long ramble, my questions are
1) Has anyone tried this before, if so what did you find out etc.
2) Is this dangerous to run?

Cheers!

Welcome to Lighting Gallery!  I'm a fan of mercury vapor lamps and NEMA bucket fixtures, myself. I have a home made 50 watt MV fixture which I use occasionally.

What you're doing is not dangerous, but it is destroying the MV lamp. A 175 watt MV lamp requires about 1.4A of current. If I remember right, a 50 watt HPS requires about 0.7A. So the MV lamp is only getting half of its rated power. When fluorescent lamps and discharge don't get enough power, it harms the cathodes and shortens their life.

Some metal halide lamps are compatible with HPS ballasts, but to my knowledge no MV lamps are. Someone here might be able to send you a proper MV ballast if you ask on the Wanted section of the forum.

Trent

Hey thanks for the reply.
Im glad to know that using this light for dusk to dawn operation is not dangerous and will only shorten the life of the bulb.

Im ok with that as the clear E shaped 175w MV bulbs are very easy to come by and I have several. Would it be safe to assume that using this bulb with this ballast will only shorten the bulb service life and not affect the ballast life?  If I remember correctly that 50w hps ballasts are easy to get but I dont want a $55 ballast to go up in smoke lol.

Thats cool that you custom built a 50w MV bucket light as this is what Im pretty much after, a vintage worn out looking,  but functional Nema head MV fiixture thats not the typical 175w configuration as this is way to bright for my backyard.

I was very surprised to see the 50w hps ballast strike an arc and light up the 175w MV bulb. Every professional electritian I taked with said this would never work and the bulb would explode and or fry the ballast!

I have posted a wanted ad for a high hour or worn out so to speak 175w MV bulb that has turned green to complete my Nema head fixture project. Maybe I should post a wanted ad for a 50w MV bulb and matching ballast.

Thanks for your time and I look forward to making more posts and chatting with more members. I will post some pics asap!

Hello there ,  i. Have expermented  whith MV lamps as well,  100 watt nema fixture will show up in ebay once in a blue moon, far as runing  mv properly i have been using MH ballast with out ignotors works well

Ballast  to mv lamps
39 watt MH for 50 watt MV
70 watt  MH  100 watts
150 watt mH to 175 MV lamp

There are few differences to consider:
These low wattage HPS are of rather low arc voltage designs (~60V roughly, +/- 10V or so), the only reason for that is to suffice with just a simple series choke as a ballast for normal operation with the 120V mains voltage as an OCV.
On the other hand the MV's are designed with an arc voltage of ~110V, so need ~200V or larger ballast OCV and that mean you need a step up transformer as part of the ballast functionality.

Normally the OCV shall be at least twice the arc voltage, so the arc would be stable on that ballast (hence the ~60V arc with the HPS for the 120V territory). And believe me, going below means the arc really extinguish after a while (or not ignite at all).

Now what happens with your setup, when it apparently operates for a long time? There are two basic scenarios:
- The MV bulb never reaches the unsaturated vapor state. When cold, most of the mercury is liquid, so the pressure is low, so the arc voltage is low as well. That means the arc could burn well, the 120V mains is more than twice the actual arc voltage. But as the bulb warms up, more mercury evaporates, the pressure goes up, so the arc voltage rises. With that the circuit current drops, preventing the further heating up, so the system stabilizes. But the arc is just on the border of extinction, but apparently there is no "knock" in your mains to "tip it over", so it operates... As this would mean quite high sensitivity for lamp extinctions, so for normal duty it could be called anything, but never "reliable". But for your purpose that does not have to be a problem, as I understood is as just a decoration.
With this the ballast operates below the rated current, so it would operate way colder than designed for, so no problem from that direction.
But beside the choke, the HPS ballast contains a HV pulser, an igniter, designed to deliver  few pulses needed to ignite the lamp, hence it is designed to be active for just few seconds per start (plus exceptionally some minutes when the lamp fail, but that does not happen for too long, when comparing to the overall life of the system).

- The arc in the MV lamp actually extinguish on it's own, but it could be this pulser, what kicks in and every half cycle reignites the arc. Externally you won't notice with modern ignitors, as these are designed to pulse at least once per each mains half cycle. But it means the pulser is actually active (pulsing) all the time the lamp is ON. It would be  no big deal for the lamp (the discharge itself makes sure the voltage get clamped to something similar the normal 200+OCV ballast, so safe for the lamp internal structure), but you will eaten up the ignitor's life very quickly, so after some time the ignitor will give up.

I do not believe the first scenario alone is realistic, in that state the arc has so "shaky legs" I doubt it will hold for too long - first dip in the mains shut it down.

I would guess your lamp is operating on some kind of mixture of both effects: The current drops when it heats up and the ignitor takes care of a reignition after mains zero cross. In any way I see your ignitor in the HPS ballast as the weakest link in that setup, needing quite frequent replacements. The components inside that ignitor should be possible to buy for $5 or so, so get ready for that and stock spares (mainly the Sidac and capacitor)...

Even the lamp won't be as bad on it: The cathodes have so steep dependency between power dissipation and temperature, you need to change the power dissipation an order of magnitude to get the temperature significantly different, so it should last quite some time.

So the only problem I see with the ignitor life, otherwise there should be no problem.

Hello there ,  i. Have expermented  whith MV lamps as well,  100 watt nema fixture will show up in ebay once in a blue moon, far as runing  mv properly i have been using MH ballast with out ignotors works well

Ballast  to mv lamps
39 watt MH for 50 watt MV
70 watt  MH  100 watts
150 watt mH to 175 MV lamp

Really?, are these 100w fixtures the all cast aluminum  with the slipfit pipe wall mount, twist lock photot and snap on shade? I know regent and a fiiew others made a "small" bucket light style fixture in 100w MV  with the angle bulb, integrated wall mount and mini photocell,  or are these the type that might be on ebay from time to time?
Thats cool to know that you can run MH ballast without using the canister thing to run MV bulbs. I didnt know their was a 39w MH ballast ot bulb around

There are few differences to consider:
These low wattage HPS are of rather low arc voltage designs (~60V roughly, +/- 10V or so), the only reason for that is to suffice with just a simple series choke as a ballast for normal operation with the 120V mains voltage as an OCV.
On the other hand the MV's are designed with an arc voltage of ~110V, so need ~200V or larger ballast OCV and that mean you need a step up transformer as part of the ballast functionality.

Normally the OCV shall be at least twice the arc voltage, so the arc would be stable on that ballast (hence the ~60V arc with the HPS for the 120V territory). And believe me, going below means the arc really extinguish after a while (or not ignite at all).

Now what happens with your setup, when it apparently operates for a long time? There are two basic scenarios:
- The MV bulb never reaches the unsaturated vapor state. When cold, most of the mercury is liquid, so the pressure is low, so the arc voltage is low as well. That means the arc could burn well, the 120V mains is more than twice the actual arc voltage. But as the bulb warms up, more mercury evaporates, the pressure goes up, so the arc voltage rises. With that the circuit current drops, preventing the further heating up, so the system stabilizes. But the arc is just on the border of extinction, but apparently there is no "knock" in your mains to "tip it over", so it operates... As this would mean quite high sensitivity for lamp extinctions, so for normal duty it could be called anything, but never "reliable". But for your purpose that does not have to be a problem, as I understood is as just a decoration.
With this the ballast operates below the rated current, so it would operate way colder than designed for, so no problem from that direction.
But beside the choke, the HPS ballast contains a HV pulser, an igniter, designed to deliver  few pulses needed to ignite the lamp, hence it is designed to be active for just few seconds per start (plus exceptionally some minutes when the lamp fail, but that does not happen for too long, when comparing to the overall life of the system).

- The arc in the MV lamp actually extinguish on it's own, but it could be this pulser, what kicks in and every half cycle reignites the arc. Externally you won't notice with modern ignitors, as these are designed to pulse at least once per each mains half cycle. But it means the pulser is actually active (pulsing) all the time the lamp is ON. It would be  no big deal for the lamp (the discharge itself makes sure the voltage get clamped to something similar the normal 200+OCV ballast, so safe for the lamp internal structure), but you will eaten up the ignitor's life very quickly, so after some time the ignitor will give up.

I do not believe the first scenario alone is realistic, in that state the arc has so "shaky legs" I doubt it will hold for too long - first dip in the mains shut it down.

I would guess your lamp is operating on some kind of mixture of both effects: The current drops when it heats up and the ignitor takes care of a reignition after mains zero cross. In any way I see your ignitor in the HPS ballast as the weakest link in that setup, needing quite frequent replacements. The components inside that ignitor should be possible to buy for $5 or so, so get ready for that and stock spares (mainly the Sidac and capacitor)...

Even the lamp won't be as bad on it: The cathodes have so steep dependency between power dissipation and temperature, you need to change the power dissipation an order of magnitude to get the temperature significantly different, so it should last quite some time.

So the only problem I see with the ignitor life, otherwise there should be no problem.

Hey thanks for sharing all that detailed information,  you deffinatly know your HID lighting theory and I was hoping someone one here would break down my particular set up  so I could understand this for myself.

So if I understand correctly, the ignitor or capacitor is the component in my lamp ballast that is getting abused and will fail? I thought that part was seperate from the steel laminated stack assembly that has the windings of wire inside? My 50w HPS ballast has no other external parts to it, just the steel heavy thing with 4 wires comming out of the centre.  Lamp has been on dusk to dawn for over a month now.

I would like to make this last and im willing to change components, I basically have everything I need except a high hour blackened arc tube 175w clear end delux white MV bulb. I know someone has to have one in their collection lol. I posted a want ad but no replies yet.

The capacitor that Medved is talking about is the one inside the ignitor, not the power factor correction capacitor. Basically treat what he's saying to mean that you could kill the ignitor.

Your ballast is the all-in-one variety which has the ignitor and power factor correction capacitor inside it. If the ignitor blows, it may render the entire ballast useless, since I don't know if you can wire external ignitors to those types of ballasts.

The capacitor that Medved is talking about is the one inside the ignitor, not the power factor correction capacitor. Basically treat what he's saying to mean that you could kill the ignitor.

Your ballast is the all-in-one variety which has the ignitor and power factor correction capacitor inside it. If the ignitor blows, it may render the entire ballast useless, since I don't know if you can wire external ignitors to those types of ballasts.

I figured that the ignitor components were contained all within the ballast itself as it is quite heavy for how small it is.

Well I dont want to ruin this good 50w hps ballast so I will take down the fixture tomarrow and see how I can find a way to achieve what im after.

Would it be possible to install a dimmer switch on a 120v 175w MV bulb and ballast? Like those push in rotary ones in the living room.

I don't know whether or not a dimmer would harm the ballast. Why do you want one?

The reason I would like to run a dimmer switch is because the Nema fixture that I would like to install is a 175w MV and this is to bright for my yard application.

Sure I could go by a new modern efficient LED fixture for my backyard but  I am not a fan of those and lI like old obsolete MV lighting, hence my want to use a vintage style Nema head.

I have 3 175 watt MV ballasts, 5 175w mougle base MV bulbs, 2 50w HPS mougle base bulbs and 1 50w hps ballast, I guess I need to collect more 

So I guess my only options are to find a matching 100/80/50 watt MV bulbs and ballasts but they are hard to come by. Every electrical supply place I call in London Ontario wont even look to see if one of their suppliers would have any leftover stock, they just want to sell HPS and MH retrofit lamps and ballasts 

I think the easiest way to achieve what Im after is to locate a really worn high burn hour 175w MV lamp that emitts the greenish light and no pinkish red during start up, I believe this bulb would have a blackened arc tube if Im correct? Lol I can think of atleast ahalf dozen or so decades old dayburners that are around my city. I can think of this one Nema style MV fixture that has been dayburning for atleast 20 or more years and is still going as I type this, its basically a green MV light now lol. Lets see LED go that long!

Metal halide ballasts work fine with mercury vapor lamps. You can use the next wattage down MH ballast for a specific MV lamp. So for a 175W lamp, use a 150W MH ballast, for a 75 or 80 watt lamp, use a 50 watt ballast, and for a 50 watt lamp, use a 39 watt ballast. Get the type that has the separately-attached ignitor and capacitor, and remove the ignitor.

My own 50 watt MV fixture uses a 50 watt MH ballast, and it's been working great. I just had to install a resistor in series with the ballast to lower the lamp current, since the lamp was being driven at about 65 or 70 watts.

Most ballasts do not operate correctly with an incandescent dimmer, that way it won't work.
And regarding the capacitor, as "TheMaritimeMan" said, I meant the inner components of the ignitor. There is a resistor of about 4.7kOhm/1..5W, a capacitor of about 220..470nF/250V and a SIDAC with trigger voltage around 100V and a small inductor (to act as a high impedance for the HV pulse, so do not load it).

The ignitor is sometimes taped together with the ballast choke, but if it fails, you may cut the tape and either repair it (in your setap that would be pretty often) or connect to it's place an external one (that would be prefferable solution for your case, as the external would be way easier to repair)

I just aquired a old MH 70w indoor fixture from my auto dealership and was wondering if I could remove the capacitor and ignitor and use just the ballast to run a 175w mercury vapor bulb?

You should really use the proper ballast and lamp with matching ANSI code unless operating a mercury lamp on a metal halide ballast as mentioned above. Ive seen countless relamping misapplications that ended badly...ballasts cooked, capacitors melted. And those bad failures were all caused by using a lamp with a higher rated wattage than the ballast's rated wattage in the fixture, not the other way around. For example, an M59 400w halide on a M58 (250w) or lower wattage ballast. I see this often as people are ignorant and the ballast almost always fails with a overheated charred-black primary. So I would advise against using a higher wattage lamp on a lower wattage ballast. The only exception would be again, a mercury lamp on a MH ballast such as a 150w (M81) ballast driving a 175w (H39) Lamp.

And I have plenty of end of life, super dim, greened-out mercury lamps that arent brighter than a 100w incandescent, but they are all 400w and most wont start without an ignitor, such as on a pulse start MH ballast