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View Full Version : Dimmable metal halides??


TheGrog
11/02/2007, 06:17 PM
I was surfing around and I came across some Coralvue Dimmable MH ballasts for sale.

Anyone know about these?

If so, how does dimming affect the bulb life?

My intuition tells me that dimming a MH bulb cannot be good for it.

Thanks

slowsoaks
11/02/2007, 07:21 PM
Good luck, I have posted about this with little response. Someone is using a coralvue 400 and seems to like it. At MACNA Sanjay Joshi mentioned something about mh being dimmable to about 40% or so, not sure of the specific amount but it didn't seem too encouraging.

PaulErik
11/02/2007, 07:25 PM
Metal halide lamps can generally be dimmed. The recommended way is to start the lamp at 100% and let it stabilize for a minimum of 15 min. Then the lamp can be dimmed down to a maximum of 50%.

Starting the lamp dimmed or prolonged low end dimming has shown in commercial studies to affect lamp life and light output over time (increased drop in light out over time).

SlowCobra
11/02/2007, 08:53 PM
I believe the ballasts dim up to 30%.

PaulErik
11/02/2007, 09:00 PM
The lowest dimming setting will depend on the lamp (wattage and type) and ballast. Most common is 50% maximum (power wise not light output).

Some of the high end commercial pulse start metal halide systems can go down to 30% but you must use approved/compatible lamps and ballasts.

pjf
11/02/2007, 09:01 PM
I don't know if dimming a metal halide lamp reduces or enhances its longevity. My gripe about MH dimmable ballasts (http://www.coralvue.com/metalb.html) and fluorescent dimming ballasts (http://www.naturallighting.com/web/shop.php?crn=623, http://www.aquariumpros.com/p-SOL750,LFvb.html) is that the dimming controllers tend to be manual. Notice that the Coralvue ballast depends on a manual knob for dimming.

Many aquarists are hoping that computer-dimmable LED fixtures come down in price.

NewSchool04
11/02/2007, 09:22 PM
I have these ballasts (3 400W Coralvue) and the dimming of the bulb does one thing that no one really talks about. It changes the color of the bulb. I use 10K Reeflux bulbs and when I dim them they change color towards a 20K look. It doesn't feel like the bulb is getting dimmer, just a different color.
I'm not sure what effect it has on either the bulb or ballast but it definitely has an effect on the light reaching the corals. I do it every now and then just to change the look of the tank.

JCTewks
11/02/2007, 10:06 PM
with a little EI ability you could easily replace that manual pot with something that you could use your controller to dim!

TheGrog
11/03/2007, 07:38 AM
<a href=showthread.php?s=&postid=11107057#post11107057 target=_blank>Originally posted</a> by JCTewks
with a little EI ability you could easily replace that manual pot with something that you could use your controller to dim!
Now THAT is a DIY projcet I would love to see!!!

JCTewks
11/03/2007, 10:36 PM
I bet Giovanni could figure it out :) (He's the one with the "Aquasurf your Vortec, the DIY" thread)