Difference between DE and Mogul based MH?

[BlueAbyss]

Hey everyone, I was wondering what everyone's experiences with Metal Halide lights are... Is there a difference between HQI and Mogul based bulbs, other than the glass envelope around the Mogul bulbs? I realize there must be a glass shield over the HQI bulbs to filter out UV, but is there a difference otherwise?

[Skimmerking]

i have read that the HQI is actually just a DE bulb. the HQI is the ballast type that runs it.

the Mogul bulbs do get air in the bulb when its made. the DE doesnt get any air due to it being vacum sealed the SE are not....

[BlueAbyss]

Hmm yes I knew this... actually, I think SE or mogul based bulbs are filled with an inert low expansion gas. I was just curious if one was different than the other, like if the light spread is different or what?

Upon further investigation, I think that a DE bulb (thanks asmodeus you got me thinking ) is actually the same as a SE bulb but without the glass envelope. So really, 2 bulbs made by the same manufacturer and with the same elements but one being SE and the other DE should put off the same quality of light.

HQI refers to how the bulb itself is built (Hydrargyrum Quartz Iodide). There are also HMI (Hydrargyrum Medium-arc Iodide) and other types of HID lighting systems, but they share the ballast and arc-tube design.

[Myka]

The main differences in performance between the bulbs are that the DE bulbs are more intense for the wattage, but spread their light over a smaller area. They also have more "hot spots". SE bulbs are less intense, but spread the light over a larger area, and have fewer hot spots. Many SE bulbs can be run on HQI ballasts which overdrives the bulb and actually makes the SE bulb more intense than the DE, however this wears the bulbs out a bit quicker, and you should consider replacing them every 8-10 months instead of the usual 12 months for MH bulbs that are operated normally.

Is that the answer you were looking for?

[BlueAbyss]

YES INDEED! That's exactly what I was looking for, thank you! I was looking at ballasts last night, and I'm thinking I'll get a HQI ballast and run a SE bulb, since I may end up with a 36" long tank in the end. I have no problem changing bulbs every 9 months, and I've heard of people having excellent results overdriving bulbs. Also that would give me the option to go to DE bulbs eventually if I decided I wanted to go that route.

My other option is to just buy a normal electronic ballast, because I think I would have some energy savings over the core and coil type HQI ballasts... unless I can find an electronic HQI ballast? I've never seen a ballast described that way, so I'm not sure if these exist.

Also, I'd like to find a 70W ballast if I stick with the 24" long tank, as I'd rather just run T5HO for the main light source in that case and have the MH as more of an accessory and for the ripple effect. 150W over a 20 gallon high seems like a lot, but maybe not since I do plan to have some SPS eventually. And definitely not too much if I do get the 36" tank.

[fkshiu]

There's no such thing as an "electronic HQI ballast". When dealing with MH ballasts there are four basic types:

1. Magnetic probe start (aka TAR or cap and coil)
2. Magnetic pulse start
3. HQI
4. Electronic

Generally speaking, you'll get the most PAR out of HQI ballasts but they will use a lot more energy at the same time. Electronics use less energy but put out a bit less PAR. Magnetics are in the middle usually. Electronics are smaller, lighter, make no noise and generate very little heat.

SE bulbs are pretty much jacketed DE bulbs. This allows SE bulbs to be run without a separate glass UV shield which DEs require. The shield can cut down on PAR.

Different bulbs may require different ballasts. For example, most European SE bulbs require a pulse start ballast because they have no internal ignitor. Electronic ballasts can run any bulb of the stated wattage.

Certain SE bulbs, like the Radium 20K 250w, are specifically designed to run on an HQI ballast. Therefore, you are not overdriving them at all on an HQI ballast and they will last a lot longer than 9 months.

A good resource to help you decide on your bulb/ballast combo is Sanjay Joshi's site:

http://www.manhattanreefs.com/lighting