MH lamp installing question (1 Viewer)

[h2oimports]

I am replacing my mh bulb with a xm 20 k bulb. My question is does it matter which side of the mh bulb faces the tank? there is a dot in the middle of the arc on one side, letters imprinted on the bulb is on the same side. I am confused because my previous bulb is a ushio . and the letters and dots in the arc is on opposite sides. Which side should i have the bulb facing the tank? thanks

 

[mpwolken]

Is this a screw type bulb? DE bulbs can only be installed one way.

 

[h2oimports]

it is a DE . i dont know which way. looks like it can be put on both ways. im just wondering if it matters which way the bulb can face since there is a little bump on one side of the arc.

 

[mpwolken]

Really, what wattage? The 250's I've used are designed to fit in one direction.

 

[h2oimports]

70w

 

[mpwolken]

OK; sorry, I'm not familiar with the configuration of those bulbs.

 

[h2oimports]

thanks though mpwolken

this is a pic of an example

 

[h2oimports]

it works both ways when i fire it.

 

[mario8402]

pretty sure the nipple should face down

 

[AquaNerd]

no, the "nipple" should face up.

it is a tiny air vent that allows hot air to escape that portion of the bulb. if you leave it down, it will reduce the life of the bulb.

 

[h2oimports]

Ahh. Thanks so much !

 

[karlo]

some more info:
http://www.advancedaquarist.com/2002/3/review

 

[AquaNerd]

that's an interesting article karlo. too bad it's inconclusive for the most part.

the reason i say "nipple up" is because the literature that came with my ballast (or could have been bulb or reflector, i forget) says nipple up. the reasoning behind what they said made sense. also, if you try to install a single ended bulb, i think it ends up pointing upward no matter how you screw it in. i tried countless times to get the nipple to face downward during installation just to see if it could be done, but it always ended up facing the reflector. but i guess it all doesn't matter...it just depends on the bulb according to the article.

 

[AquaNerd]

interesting article on rc

http://www.reefcentral.com/forums/showthread.php?t=1527871

 

[jamesw]

The "nipple" is the "bloop" where the metal halides were injected into the capsule. It also helps w/ heat transfer like Brandon said.

Richard's article basically "says" it doesn't matter. I personally try to orient it so that the nipple faces up and any glass or metal wires don't interfere w/ the light path.

Cheers
James