MH & Heat

[Mike31154]

Other than the warming effect on your tank water, is there any benefit to cooling MH lamps? Do they run better/longer when actively cooled like T5HO? I recently installed a number of small fans to cool the ends of my T5HO lamps since this is reported to make them last longer and run more efficiently. Prior to that I was using two larger fans to blow across the water surface underneath the lighting in an effort to cool the Halides and T5HOs. I found this to significantly raise my evaporation rate, but am unsure of any benefit to the lights. Just wondering if it's worthwhile to actively cool a typical 250 watt SE MH lamp, or if it's better just to let 'em run as hot as they want, provided they don't heat up your water to the point of requiring a chiller. I suspect the heat build up is even more of an issue with DE halides behind a glass cover?

Did a bit of a net search on the subject & there's plenty of techno talk about how MH lamps and ballasts work etc., but not much on the cooling aspect or if it's required/beneficial. Maybe there's more info to be found with our horticultural friends, although they use even higher wattage lamps, generally 400 plus. I did come across a site that showed pendant/reflector housings which accomodated fair sized cooling ducts through the sides. Cooling for that application may be necessary to keep from cooking the plants, not necessarily for lamp efficiency or life.

 

[slief]

I would say that any device that produces that much heat will benifit from running cooler and in the case of a bulb, longevity would be the key benifit. Many of the high end MH pendants have optional cooling ducts that can be built into the reflectors. My Luminarcs are a good example.

I dont use the ducts as I am not using the glass and have a large high CFM fan that draws from the space above my tank and sends the heat through the wall outside the house.

 

[EnderG60]

based on my experiance without fans in a open top canopy you get about 1/3 to 1/2 the halide wattage in the water as heat. Sealed canopy no fans its 1/2-2/3. With fans its less then 1/4.

A small fan blowing across the water under each bulb, and another exhausting the hot air will keep the heat absorbtion pretty low.

 

[Mike31154]

Thanks for the thoughts 'slief' and nice set up there.

I built two DIY lumenarcs using the solar tube reflective aluminum and had no idea there was an optional cooling duct available for the commercially produced item. As mentioned, I did come across a web site on the horticultural side of things showing fair sized cooling ducts entering and exiting the reflector housings. One of the tradeoffs there would be the loss of reflective surface used up by the holes for the ducting.

I too assume cooling is beneficial but am looking for something a little more technical or scientific to confirm that it's worthwhile. I thought one of the principles of proper operation of a MH lamp was the high voltage (perhaps translating to heat) required to 'strike' the bulb?

Thanks again and if you find the time I wouldn't mind seeing a few more shots of that lighting set up you have.

 

[Mike31154]

based on my experiance without fans in a open top canopy you get about 1/3 to 1/2 the halide wattage in the water as heat. Sealed canopy no fans its 1/2-2/3. With fans its less then 1/4.

A small fan blowing across the water under each bulb, and another exhausting the hot air will keep the heat absorbtion pretty low.

Thank you for sharing this experience. However, I'm not concerned about heat transfer to the water at this time. In fact, I haven't been running the larger fans I spoke of in my initial post for some time now. I do not have a canopy, I'm running open top so heat transfer from the MH is currently not an issue, perhaps in the summer when the room temp is higher again. What I'd really like is confrmation that cooling the MH lamp will make it last longer or produce more useful light.

 

[slief]

Here are some more. I picked my arcs up used. One had the vents and the other didnt. The vents have a cover on the inside which is made of the same reflective material as the rest of the fixture and mitigates any reflectivity loss. I dont have any good pics of the little cover on the inside but I can get when I get home if you would like.

Here are a couple more pics. My light rack is raised and lowered with an electric winch. There are cables attached at all 4 corners which are run through pullies to the winch location which is in a closet next to the tank. You can see the cables in the pic above as well as the one below.

The winch setup.

Winch cable routing and the ventilation ducting routed from the tank through the wall. The large rotron fan is mouted to the tank side wall and the duct goes over it. This pics is looking straight up at the ceiling in the closet.

 

[Mike31154]

Awesome, that's pretty slick. The pulley system caught my eye right away in your initial photo. I like the use of wood for the frame too, I gather that the stuff in the hood is treated with some form of moisture proof coating?

Thanks for all the photos, that winch set up is something I'd like to consider for my next upgrade. If you have a build thread or photo album in your profile, I'll check it out.

My lighting set up is somewhat ghetto at the moment, I used square aluminum stock for most of it. A couple of shots follow. The larger AC fans you see at the end are the ones I'm no longer running. I've installed much smaller 12 volt DC fans directly over the ends of the outer T5HOs and have removed the middle T5HOs since these photos were taken. For a while I was removing and installing the two center T5s every day for my lighting schedule, that became too much of a hassle so now I run the outer T5s in the morning and evening and the MH during the midday period with no T5 supplementation. Seems to work fine with the Softie & LPS collection I have.

 

[slief]

Awesome, that's pretty slick. The pulley system caught my eye right away in your initial photo. I like the use of wood for the frame too, I gather that the stuff in the hood is treated with some form of moisture proof coating?

Thanks for all the photos, that winch set up is something I'd like to consider for my next upgrade. If you have a build thread or photo album in your profile, I'll check it out.

My lighting set up is somewhat ghetto at the moment, I used square aluminum stock for most of it. A couple of shots follow. The larger AC fans you see at the end are the ones I'm no longer running. I've installed much smaller 12 volt DC fans directly over the ends of the outer T5HOs and have removed the middle T5HOs since these photos were taken. For a while I was removing and installing the two center T5s every day for my lighting schedule, that became too much of a hassle so now I run the outer T5s in the morning and evening and the MH during the midday period with no T5 supplementation. Seems to work fine with the Softie & LPS collection I have.

Thats a nice system you have there too!!

The wood is not treated.. Just typical pine 2x2's from the lumber yard. Its been in action since 97 and held up fine. I am going to change it out soon and make an extruded aluminum frame similar to yours... I already have a list of parts that I would need from EZ TUBE to do the job.

No album here yet and no build thread but I will be doing a build thread in the next couple weeks as I am about to rip my wetdry system out and replace it with a pair of 30"x40" sumps that will act as a fuge for my system. When I do that, we will take a bunch of photographs which I will use to document the change as a thread here and also use that thread to cover the tank from its original build to the various changes and upgrades over the years.

It will also be video taped for an episode of LA Fish Guys. Jim, the guy that makes those videos is a friend of mine and does the cleaning and maintenance on my tanks as I can get pretty lazy. He is coming by tonight and we are doing a 100 gallon water change/vacuuming which we will video tape and it will be used as a precurser to the sump retrofit. I will post some links to those videos in my build thread as well.

 

[Mike31154]

Great, I'll be watching for those upgrades. Aluminum for the frame is a good choice. Little chance of corrosion, light, strong and easy to work with. I used stainless screws to hold it together and nylon screws/nuts to mount the T5 endcaps so there should be no issues with rust etc. I also tapped and threaded all the holes for the stainless screws, eliminating the need for nuts/washers etc. Used 3/4 inch square and angle stock. If I were to do it again, I might go with 1 inch and run the wiring through the tube. Drill more holes and feed the wires through grommets in the holes for a cleaner look. I could probably do that with the 3/4 inch stuff as well, but since I'm upgrading soon (I hope) I've let some of these things slide.