How to build your own High Pressure Sodium and Mercury Vapor Lights pt. 2

The following is a brief description of exactly how I made my 100 watt mercury vapor unit and what you would need to create your own. I have also included photos taken under my new mercury vapor unit and photos of the unit itself.

Mercury vapor units burn a very distinct green to greenish-blue color. They were used for the most part in industrial/commercial applications.

I hesitate to even post this entry because, as of last year the US government banned the sales and import of any new mercury vapor ballasts and fixtures. It took me roughly two weeks to locate a used mercury vapor fixture and it was a much smaller unit than I had hoped for. The bulbs for mercury vapor ballasts are still available and to the best of my knowledge still being manufactured. As of today, only the sale of new ballasts have been banned, you can still purchase the bulbs.

During my quest to build a mercury vapor unit I learned many interesting facts, such as mercury vapor bulbs will only work properly in the exact wattage fixtures they are made for. i.e. a 100 watt mercury vapor bulb can only be used in a 100 watt fixture and a 400 watt mercury vapor bulb can only be used in a 400 watt fixture. It is not like an incandescent bulb where a fixture is rated up to a maximum and smaller bulbs can be used in that fixture. If you use a smaller bulb i.e. 100 watt mercury vapor bulb in a 400 watt fixture you will shorten the life of the bulb.

I also learned that while it is not the best solution, existing mercury vapor bulbs can be run in new metal halide fixtures. I had a lot of problems finding mercury vapor bulbs with the right base to fit into a metal halide fixture, as most metal halide fixtures have medium bases and most mercury vapor bulbs have what is called a mogul base. A mogul base is considerably larger than a medium base.

One last thing to consider is that a mercury vapor bulb needs a built in ballast to properly regulate the voltage. This is why you can’t screw a mercury vapor bulb directly into a household socket. If you tried the bulb could explode, but would very likely flicker like crazy and burn out. They do make self-ballasting mercury vapor bulbs, these are mercury vapor bulbs that can be screwed into more common fixtures. The problem I have with these bulbs is that they all have an internal deluxe white coating which color corrects the bulb. This means that amazing greenish-blue color we are after is now washed away by dull white light. Many of the non-ballasted bulbs have also begun going the deluxe white route, so if you are attempting to build your own unit, be sure to purchase only clear mercury vapor bulbs.

The Components:

You’ll need 7 components to make a very basic 100 watt mercury vapor “film type fixture.”

1. (1) 10 Watt High Mercury Vapor Fixture ($15.00 - $180.00)

2. (1) All Weather Outdoor Outlet Box with top ($5.40)

3. (2) Nuts, Bolts and Washers ($0.99)

4. (2-3) Wing Guard Twist on Connectors ($0.17)

5. (1) 6’ Garbage Disposal Cord ($3.22)

6. (1) 100 Watt clear Mercury Vapor bulb with mogul base ($24.00)

7. (1) 1-1/2” Electrical Clamp ($1.79)

Total Cost: $48.79 - $213.79 per unit.

We begin by separating the top portion of the outlet box from the bottom half. The top portion of this box is actually a heavy metal light switch cover. Since the cover is not designed to be affixed to the lighting fixture, I had to drill two ¼” holes. In order to do this I held the cover up to the fixture and marked where I would need to drill with a Sharpie permanent marker.

(¼” drill bit)

(The box is marked with a sharpie before the holes can be drilled)

(Box with holes drilled)

Once you’ve drilled the holes through the plate take the wires from the fixture and pull them through the threaded hole in the center of the plate. You can now affix the plate to the fixture with the ¼” bolts.

(1/4”) bolts attaching the plate to the fixture)

Screw the ½” electrical clamp into the backside of the all weather outdoor outlet box. By doing this you will be able to set the unit down flat without putting strain on the cord.

(½” electrical clamp, pictured on the top of the box, in the final build the clamp has been relocated to the rear of the box)

Now take the 6’ garbage disposal cord and thread the exposed end of the cable through the clamp you just inserted and into the bottom portion of the outlet box.

Next, move on to attaching the neutral wire from the fixture, which is usually white to the neutral wire of the garbage disposal cord. In this case the neutral line of the garbage disposal cord was not color coded. The neutral line can sometimes be identified by looking at the end of a polarized plug to see which blade is “fatter.” The “fatter” blade is generally connected to the neutral lead. Once you have found the neutral wire from both the fixture and the garbage disposal cord, twist them together with a wing guard twist on connector, and then tape securely with electrical tape.

After the neutral line is secured, you will need to attach the 120V hot leads together from both the fixture and the garbage disposal cord. This wire is generally coded black. The garbage disposal cord once again did not have any sort of markings on it. I was able to determine it was the hot lead based on the fact that it ran to the “skinny” blade of the plug.

(Hot and neutral leads from fixture and cord attached using wing nuts)

On this unit the ground from the fixture was already attached to a screw on it’s exterior support arm. With a screw driver loosen the screw holding the ground just enough so that you can loop the ground from the garbage disposal cord around the ground screw and tighten down, making sure neither wire slips loose.

Now that you are wired up, you’ll want to secure the garbage disposal cord with the ½” clamp so that the wire can not be pulled free. Tighten the clamp down till it holds the wire firmly in place but not so tight that it punctures the wire's protective coating.

You are now ready to screw the top and bottom halves of the outlet box together.

To round out the completion of my Mercury Vapor “Film Type” unit I attached a Cardellini clamp and a double baby receiver for 5/8" tubing to make the unit baby stand mountable.

Lastly, the fixture I have has a light sensor on the top that causes it to turn off when it senses daylight. To override this function I simply taped over the sensor.

(Final Mercury Vapor “film type” light)

I have included several photos taken using my new mercury vapor “film type” unit. All pictures were taken at 3200K:

(Mercury vapor “film type” unit in use)

(Mercury vapor & high pressure sodium in use with Tiffen 3mm streak filter)

(Mercury vapor & high pressure sodium vapor in use)

Should you be willing to put in the time and effort, I think you’ll see the results are definitely worth it!

Be sure to check back in the next few days where I will be explaining exactly what mm you need to be zoomed into on your HVX-200 and HPX-170’s while using a Redrock Micro Encore to get the right mm out of the 35mm lenses you are using on your rig.