Metal Halide Questions

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Stryker

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Hi there, I hope someone here who has used MH lighting can answer a few questions for me.

I've bought a MH 150W light with control gear off ebay. £30 all in and the bulb survived the post good deal eh?

I plan to use it over a 4ft fresh water tank of mine in place of the three 30w tubes I currently have. The tank is planted.

I have the kit on test in my conservatory (away from anything flamable :) ) and all seems ok.

1) While the tube warmed up there was a little hum from the control gear. Now the tube is at full brightness all is quiet.... is that normal?

2) How hot do these things really get? If I mount it over the tank the light will be suspended about 3" under a wooden shelf.... thoughts?

3) The current bulb in it give a pure white light.... any guesses on what colour temp it is?

Any other gottchas when working MH that I should be aware of?

Thanks in advance.
 
The hum is normal, when the light first starts up it uses extra juice to spark the gases inside the bulb to ignite them.

They do get very hot, almost too hot to touch.

It's probably a marine bulb in the region of 10000k-14000k

If the bulb is a screw in one then it will be an E40 fitment & RX7 fitment for double ended type.

Do not under any circumstances plug directly into a timer. They can catch fire if you are unlucky!!!

If you want to run it off a timer you need a contactor like this.

http://www.fastlight.co.uk/shop/index.html...get=dept_2.html

You will probably find the lamp you want here.

http://www.fastlight.co.uk/shop/index.html...get=dept_2.html
 
I would say it is more likely ot not be a marine bulb, but a hardware one, somewhere in the 4000 to 8000K range (mine were 4200). This will actually be better for plants than marine bulbs with high K (though the marine bulbs with higher K are not actually as good for coral growth as a 7200K, but that's a different matter...)

I have never heard of timers catching fire on MH. After two years I have had no problem. It has fried a couple of cheap timers, but nothing major (unlike my T5 endcap catching fire).

My biggest fear will be how close they are to the water. My ones used to be around 4 or 5" from the surface and heated teh tank to a nice 33C.

The hum is perfectly normal. Mine make an awful racket as they fire up.
 
Thanks for the tips peeps. I think my bulb is a "RX7 fitment for double ended type". I also think its over 5K because it would be more yellow if it were around 4-5k would it not? However if it were 14k it would appear more blue?

I heard that about timers before.... All I can think is that some cheap mechanical timers do no cleanly cut the power off or on but in stead kind of stutter it on and off, which I can imagine would be a killer for those type of bulbs.
 
Can anyone tell me how long a RX7 tube is? I'm sure thats what mine is, except my tube looks much fatter than the RX7 pics I've seen.
 
If you go on to the marine forum www.ultimatereef.net & search around you will find at least 2 cases of I know of where timers (electric or mechanical) have set on fire using halides. It's just not worth the risk in case it happens when your out for the sake of a £25 contactor.

I blew a timer first time I ever plug one of my halides in before realising you need a contactor. However I was running 2 x 400w lamps!!!
 

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