Mercury Vapor lamps

[ransley]

I have 100w Mercury Vapor fixtures, can I put in a 50w MV bulb, I want to save a bit on my electric bill.

[terry]

Above question reads " ....... 100w Mercury Vapour fixtures ..." but then reads "can I put in a 50w MV bulb" i.e. single bulb. So not sure if there is one 'fixture'; or a number of 'fixtures'.

However: Per fixture:

a) At 10 cents per k.watt hour you will save 0.5 cents for each hour the lamp is on.

b) At 20 cents per k.watt hour you will save 1.0 cent per hour lamp is on.

So if lamp is on every night for say 10 hours;

a) 365 x 10 x 0.5 =3D 1825 cents or $18.25 saving per per year.

b) $36.50 per year

If lamp is only on occasionally the saving will be much smaller.

PS. This question sounds a little phishy! Was this a troll???????????

Note: Is ransley .......@yaoo etc. not a frequent (and knowledgeable?) contributor to this forum?

[JohnR66]

Never do this becuase the ballast is designed to deliver a certain voltage and current to the bulb. The ballast would attempt to drive the same current into the smaller bulb. The bulb could fail early or even explode. The ballast may overheat and burn out.

From what I hear, MV bulbs, ballasts and fixtures will no longer be sold in the US. Replacing it with a CFL fixture may be a better option. MV is not really a very efficient light source anyway.

[ransley]

Troll? No ive cut electricity usage in every building I run 50-60% by use of Cfls, different location of Photosensors and timers on equipment. I am 14.25 kwh and going up again, I know of no area that is in fact .10c kwh. 100w 24x7 for me costs about 10$ a month. 50w =3D about 5 a month. At 12hrs a day I will save 2.5$ a month. Since I need a new bulb anyway its adds up in commercial use when you have alot of MV lights outside. With a building, waste and my profit is paying the utility co. 30$ will get me a new Cfl and fixture and save me over the years. Its the small things you do that add up to save on utilities.

[ransley]

I thought a ballast might deliver what is demanded on it, but I dont know ballast design. A lower watt Cfl fixture is my best option, ones I saw at HD allow in water and hold it in the lens when its in a horizontal position, I need to shop.

[John Grabowski]

*If you don't mind the color, change to a 35 watt or 50 watt high pressure sodium fixture. You'll get good lighting and good life. Check out the RAB brand at rabweb.com

[Don Klipstein]

Do not put in a bulb other than 100W mercury. A 50 watt one will be overpowered, probably receiving something like 90 watts. 50 watt operates with higher mercury vapor pressure (IIRC around 6 or 7 atmospheres) than most others, and can easily explode if seriously overpowered.

To save power, you have to replace the entire fixture, or at least the ballast as well as the bulb.

Use only bulbs having an ANSI ballast compatibility code same as at least one on the ballast or fixture. Violating this can lead to overpowering or underpowering of the bulb, and/or inability to start or unreliable starting or starting becoming unreliable after the bulb has been broken in. Overpowering/underpowering is even possible with mismatch between 2 different types of same wattage - such as 2 different

150 watt pulse-start high pressure sodium versions. Check the ANSI "ballast compatibility" codes!

Also, replacing a 100 watt mercury with a 50 watt one may change the light distribution pattern because the light source is shorter and may be closer to the base.

- Don Klipstein ( [e-mail])

[Don Klipstein]

As far as I heard, the bulbs themselves are not outlawed. The following can be operated on same-wattage non-pulse-start metal halide ballasts:

175 watt H39 mercury will work with M57 metal halide ballast 250 watt H37 mercury will work with M58 metal halide ballast 400 watt H33 mercury will work with M59 metal halide ballast

However, I do agree with replacing the mercury fixture with something more efficient - preferably metal halide or CFL. If CFL is used, go for higher color temp. for illuminating outdoors at night - the spectrum of higher color temp. is more visible to night vision.

Also, get a fixture with some directivity, to put the light where you need it. That will allow a lower wattage, and also keep the "dark sky" people happier.

- Don KLipstein ( [e-mail])

[pheeh.zero]

I can only throw this out for ppl that have HPSodium fixtures...where I work we have 70W fixures and the guy before me bought 50W fixtures. I have been buying 50W bulbs (as replacements in both) and they all seem to be equally bright and no premature failures (been using them for about 3 yrs)

[ransley]

Ive had good luck with HD brand Invision, and they have a 7 yr warranty, so I might have and endless replacement supply free. I have about 70 HD cfl bulbs in use 2 years with maybe 3 burnouts , 20 on photocell full time. I am refering to 9-13w cfl and 15-22w cfl floods, all light at -10f but the floods take about 10 min at -10f to be full bright so forget the motion sensor with the floods. What was barn Voltage when it didnt fire? I am 117-120v. Often I get the HD 9w cfl at about 1$ each because of Com Ed subsidies through HD. Popular Mechanics magazine rated HD Invision Soft White in the green pack as good or better than incandesant in skin color rendition. Its an old article in the home section. With HDs 7yr warranty, try em, and make a copy of the reciept so you are covered.

[ransley]

.

Don I see you are quoted on Wikipedia, thats good. MV from what I see are 55-60 LPW about the same as CFL. What is much more efficient than that in a soft White Color for an exterior flood fixture in maybe 35w. HP sodium? I want to keep watts consumed as low as possible.

You recommend Daylight CFL for exterior light but HDs brand show a lower LPW rating for Daylight vs Soft White flood so I am confused and buy Soft White, plus I like the way they lite up residential. I wonder if the charicteristics of Daylight make it perceptably brighter even with lower LWP rating. For security lights you recommend the "Daylight" cfl rating, like HDs bulb?. You feel will they be percieved as much brighter?