When to replace halide bulbs?

[texman]

I have read a lot about the spectrum change that occurs in halide bulbs after 9 months or so of average use. I recently replaced 1 175W 10000 German bulb and left the other identical bulb (18 months old - 10hrs/d) I would post a picture, however the difference in colour is barely noticeable. Are there any studies which prove that using the bulbs for a few years impedes coral growth, or is the halide bulb replacement law just being propagated by the aquarium dry goods industry?

 

[arnjer]

How many hours have you run this bulb....has it burned in yet. I wonder if you can tell a difference in a week or two.

Jerry

 

[Jeff Hood]

I would usually change my bulbs every year and could easily notice a differance. Those were 5500 K venture bulbs. I havent had my radiums long enough yet to see how it goes.

Jeff

 

[Anonymous]

The general rule of thumb is 12-18 months for the stronger par bulbs however the blue bulbs seem to give up the ghost much faster.

A German bulb should be replaced yearly. You could easily run it longer however your electical bill will likely climb as it takes more energy to fire the bulb.

You aren't likely to visually see a large shift in the color.

 

[AnotherGoldenTeapot]

I thought the current accross a MH bulb was constant and regulated by the ballast? Once it's running, which is what it does most of the time, I can't see the age of the bulb has any impact on the power used.

The firing time may change with age, but does this even make a difference? The ballast is still in the circuit to limit current. Even if there is a difference is it material? An extra second or two isn't going to make a bean of difference compared to the 12 hour period the bulb is turned on. Even an extra 30 seconds at 50% more power would still only increase electricty consumption by less than 1% (0.6%) - you will never reach a pay-back point.

I'm sure the main reason for changing the bulbs is to restore original color rendition and output.

 

[MattM]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by AnotherGoldenTeapot:
<strong>I thought the current accross a MH bulb was constant and regulated by the ballast?</strong><hr></blockquote>

My understanding is that carbon build-up in the envelope inreases the resistance. Constant current through greater resistance means more power consumption.

 

[pcragg]

Tom, Matt,
Does the extra resistance theory also apply to electronic ballasts (Icecap)????

 

[MattM]

Good question.

The higher frequency signal going to the bulb might have some effect on the carbon build-up, but I'm just guessing.

Also, some electronic ballasts have a power factor greater than 1.00, in other words, it takes a total power consumption (bulb + ballast) of less than the bulb's rating to fire it. So in this case, I doubt it's something you need to be concerned about.