proofer

I have an outdoor mercury vapor lamp post that is from 1965. It does not work (the ballast is fried). I'm trying to buy replacement parts to make this light work again. However, after doing some research, I'm wondering: What is the difference between a "high pressure sodium" and "metal halide" ballast? Also, should I buy new "old-stock" parts or should I just buy a new lamp post altogether? I'm not for that because I have to separate the electrical from the existing lamp post, and the lamp post has a unique design that I'd like to keep. Which kit would you recommend: the high pressure sodium or the metal halide? The old bulb was a 175-watt vapor, so what wattage would I look at replacing it with? Do you think a 100-watt would be sufficient?

surrogate

High pressure sodium puts out an orange color light, while regular metal halide is slightly bluish and warm metal halide is yellowish. HPS bulbs output more light and last longer than MH bulbs for the same wattage. A 100 watt HPS outputs between 9200-10,000 lumens, while a 100 watt MH outputs between 8500-9000 lumens. A 175 watt mercury vapor outputs between 7350-8500 lumens.

If you don't mind the orange hue to the light, HPS is the best choice.

proofer

OK. No, the hue doesn't make a difference to me at all.

What is the difference between a medium base and a mogul-base in the porcelain socket as far as size? Or are they just different types?

Scuba_Dave

I'd buy a new 65w CFL floodlight = equiv 500w
Save on the electric bill

micromind

Provided there's room, a metal-halide ballast can use the same socket that a merc-vapor does. If your socket is a mogul base (larger than a regular light bulb), and you can't find 100 watt lamps with this base, you can use an adapter.

Just replace the old merc-vapor ballast and capacitor with a new metal-halide one. Make sure the metal-halide ballast doesn't have an ignitor in it. If it does, see the HPS stuff below. As long as the new lamp is the same wattage or lower, heat won't be an issue.

To go to high pressure soduim (HPS), you need a socket that's rated for 4 KV pulse. The old socket might work, but maybe not. The adapter won't work at all. The reason is because when a HPS lamp starts (also a metal-halide with an ignitor), a high voltage pulse is sent to it (usually around 2,000 volts or so), in order to establish the arc. Once the arc fires, the high current (2-3 amps) low voltage (40-60) takes over. The metal-halide (without an ignitor) sends about 250 volts to the lamp to get it started, as did the merc-vapor.

Both types of ballasts have a capacitor (with two leads), and the HPS and pulse-start metal-halide have an ignitor (3 leads) also.

This is actually a fairly simple change-over, but if you need more help, post back. There are several guys on here that can lead you through it.

Rob

proofer

Looking at my old lamp bulb, the base is definitely larger than a regular light bulb --- the old vapor bulb itself is 8 inches long. So do I need to replace the bulb socket with a new one that's compatible with a high pressure sodium, or can I use the old vapor socket? Should I replace the mogul base with a new porcelain socket made for the high-pressure sodium ballast? Or can I use the mogul base that's already there?

Or - would you just get a new light? I'm not an electrician and I don't want to get into too much. I like the existing old lamp post, though, and I'd like to save it if I could. Besides, the electrical box is already attached to this box, so I wouldn't have to do anything with that.

I'll be happy to post pictures of the lamp post, old bulb, or old fried ballast if that would help at all.

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220/221

New fixture.

CF or MH depending on how bright you want it.

AllanJ

Not counting the ability to withstand the starting pulse which depends on the exact materials the socket is made of, a mogul socket and a medium socket are the same except for size.

Ballasts must match the wattage of the lamp as well as the kind (HPS, MH, etc.) of lamp.

If you want to keep the original fixture for its styling you may be able to buy a new yard light of the kind and wattage you want, take out the socket and ballast, and install both of these in your old fixture. Then screw in the lamp and you are ready to go.

For compact fluorescent, you connect the wires directly to the socket, omitting the ballast. The lamp has the required ballast built in. However CFL's don't work too well outdoors in cold weather.

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Scuba_Dave

I have over 200 CFL bulbs in my christmas display that work without a problem
My outside lights are also all CFL's & has worked without a problem for years
People in colder climates then me report the same success
Mfg of bulb can make a difference
I use NVision, GE, Bright effects

micromind

The reason I spent so much time on the socket is because replacing the socket in an older fixture is not all that easy to do. In fact, it's somewhat difficult in any fixture.

Most of the older fixtures have the socket mounted to a steel plate of some sort using two screws. They are farther apart on the mogul sockets. If you're going to replace with a different type of socket, you'll almost certainly need to drill and tap at least one, usually both holes. They need to be done right, because if the mounting screws aren't seated properly, either the socket will break, or the lamp will very likely short to ground. Especially a pulse-start type. Like HPS.

I must admit though, the color rendition of HPS can look pretty good in an older fixture!

Rob

P.S. If the self-contained CFLs have a standard base (most do), adapters form mogul to standard are usually easy to find. Just get rid of the old ballast and capacitor completely, and connect the power wires to the socket leads, screw in the CFL, and you're done.

evapman

I'd say replace the whole fixture, cost about as much as ballast and then you would get all new stuff. Would lean to mercury vapor lamp or HPS. the bulbs are cheaper to replace about $10.00-$15.00
MH bulbs are in the $30.00-$50.00 range. but either way it should last 20+ yrs.

J. V.

Yes, replace it. It will cost less this way. If you want to keep the antique, you can buy the whole kit. Ballast, starter and mounting brackets. You might have to modify the mounting parts since your fixture is so old. You also need to make sure the ballast and starter will fit inside the fixture.

proofer

Thanks for all your ideas. I went to a big box store this afternoon and spoke to the guy in the outdoor lighting department. He had some ideas as well. He said for me to first check the voltage to see if it's 120, 208, 240, or 277 volt, and to be sure I match it correctly. He then recommended that I get the 100-watt high-pressure-sodium balast kit to convert it over. In this kit, I'll be getting the ballast core and mounting, igniter and capacitor, 100-watt lamp (mogul base), and porcelain socket (mogul base). It's a lot to put together (for me, at least), so I know I'll be back here for help in the installation of it. Your help and advice is really appreciated.