Metal Halide lighting question

[Zero102]

This may be a stupid question but I am kind of new to Metal Halide lighting.

I am growing a couple of citrus trees indoors under a 250W Metal Halide light I bought last year. The bulb in my fixture was made in 1999, I bought the fixture complete in Jan. 2009, and it has run 16 hours a day every day since then. Since I have put ~7000 hours on the bulb and it was used when I bought it I suspect this bulb is near the end of it's life. I just learned how much these things dim over their lifetime and using a couple of charts I found online it seems to indicate that by the 7000 hour mark my bulb will be producing about 45-50% of it's initial light output, and since it is probably much older than that (the bulb was quite black from use when I got the fixture) the light output is probably 40% or less.

I have 2 spare brand new 175W MH bulbs in my closet, and I am wondering if it is safe to use them in the 250W fixture? Will it damage the 250W ballast or destroy the bulb, or would it function perfectly fine as a substitute until I can find a new 250W MH bulb?

Also, does anybody know a good local place to get a new 250W MH bulb? If it matters it is the ED28 size, has an E39 base and is mounted horizontally. I found a seller on EBay in Ontario for ~$25 and was going to order from him but I know it will take 2 weeks or more until the bulb gets here, hence my question about the 175W bulb as I now feel a bit rushed knowing how crappy the current bulb is.

Thanks for any help :)

[AndyL]

Depends on the ballast you're running - some of the better digital/electronic ballasts can run a 175 instead of a 250 - but most wont...

That seller out of ontario - expect within a week :) I've bought a few bulbs for the aquarium out of him...

[Cos]

I dont know specifics about your exact bulb, but I know that utilities switched from MH to HPS lights in the 80's and 90's because the LLD and LDD is high. Everything I design with now is HPS so if it works for your application I would see how hard it may be to switch to them.

As for the ballast, I would think it depends on the type of ballast. Some of them are variable (all the way up to variable voltage) but some of the cheaper ones need specific current to fire properly so it may not work.

Sorry my answers are so vague but unless you know what the maker is I could pull some spec sheets.

Also I doubt that you have losses up to 50% already. I would just leave the 250w in the fixture until it dies or your new bulbs come.

[Zero102]

I suspect the bulb has close to 10,000 hours on it (again, I put at least 7000 on it) and each of the charts I can find for light output vs hours for MH bulbs (directly from the manufacturers) shows ~50% or less after 7500 hours.

The ballast in the fixture is a very old magnetic ballast, it does not have an electronic ballast, however there are no labels or writing of any kind on the ballast itself so I cannot say much more than that.

AndyL, good to know he is that quick :)

Is there anywhere local to get a 250W MH bulb that won't charge me more than ~$25 for it? Or should I just order the bulb and stop being an idiot?

[Cos]

Originally posted by Zero102
I suspect the bulb has close to 10,000 hours on it (again, I put at least 7000 on it) and each of the charts I can find for light output vs hours for MH bulbs (directly from the manufacturers) shows ~50% or less after 7500 hours.

The ballast in the fixture is a very old magnetic ballast, it does not have an electronic ballast, however there are no labels or writing of any kind on the ballast itself so I cannot say much more than that.

AndyL, good to know he is that quick :)

Is there anywhere local to get a 250W MH bulb that won't charge me more than ~$25 for it? Or should I just order the bulb and stop being an idiot?

Oh okay then it is possible that your output is low, but if the bulb is inside then the LDD will be lower than average as well as your light levels (if you were told to use 250w) should have taken into account 85% light levels so your not as far off as you would be if you needed 250w actual out of the fixture and you had it outside in your garden for all 10,000 hours getting dirt buildup and huge temp swings.

Also an old school ballast should work with any sized bulb, but to be fair I have never worked with then, only replaced them.

[legendboy]

I don't think you loose output, isn't it just the temp that changes?

[Cos]

Originally posted by legendboy
I don't think you loose output, isn't it just the temp that changes?

http://www.lightsearch.com/resources/lightguides/lightloss.html

No the two biggest are LLD (Lamp Lumen Depreciation) and LDD (Lamp Dirt Deprecation). You can maintain some of them by having the light inside or maintenance (cleaning etc) but over time the light does loose output.

[Sailz]

Any local hydroponics stores will stock and carry a variety of MH bulbs, many specifically for growing plants (spectrum etc.).

Quick Grow is one of the better ones with a North and South Location.

www.quickgrow.com

[black_shadow_18]

could you not also try electrical wholesalers such as westburne, or Eecol, or EW?

[Zero102]

All the local hydroponics shops do not carry any bulbs under 400W, and some don't carry anything under 1000W. Also, Quckgrow makes up their prices for every customer and are a bunch of dicks FWIW, I tried to buy some 4' fluorescent lights there 2 years ago, the guys in the N.E. (I forget their name, just off Barlow trail) had them for $40/each, Quickgrow wanted $90/each and when I asked why they were more than double what the other shop was the guy said they can set whatever prices they like, and if I don't like it I should fuck off. In the end I bought them from the Kelowna Better Than Nature location on my next trip out for $22/each since they manufacture them in their shop (the exact same lights)

Local electrical wholesalers want $50/bulb or more unfortunately :(

The current fixture is located inside so there is no dirt issue, although a few flies get inside the fixture I am sure it is nothing like if it was mounted outside.

[Sailz]

Originally posted by Zero102
All the local hydroponics shops do not carry any bulbs under 400W, and some don't carry anything under 1000W. Also, Quckgrow makes up their prices for every customer and are a bunch of dicks FWIW, I tried to buy some 4' fluorescent lights there 2 years ago, the guys in the N.E. (I forget their name, just off Barlow trail) had them for $40/each, Quickgrow wanted $90/each and when I asked why they were more than double what the other shop was the guy said they can set whatever prices they like, and if I don't like it I should fuck off. In the end I bought them from the Kelowna Better Than Nature location on my next trip out for $22/each since they manufacture them in their shop (the exact same lights)

Local electrical wholesalers want $50/bulb or more unfortunately :(

The current fixture is located inside so there is no dirt issue, although a few flies get inside the fixture I am sure it is nothing like if it was mounted outside.

Too bad the Calgary retailers are like that...maybe reduced competition. Living in Kelowna I use Better than Nature and they do have EXCELLENT prices.

www.betterthannature.com