Will MH lights 5" from the water cause me to need a chiller?

J

joelq

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Hi all - I currently have four overdriven T5HOs lighting my 90g mounted in a canopy, and I'm trying to decide if switching to two 250w MHs will raise my water temperature to the point where I'd need a chiller, specifically in the coming summer months. Below are a few more details on my setup:

- my canopy is open in the back, and currently has four 80mm PC fans mounted on the sides (two on each side), all blowing in. I still have space on the sides for two more fans (for a total of three on each side). The fans are also currently running at half-speed to minimize noise.
- my canopy is not a tall one - there is 8" clearance between the underside of the top of the canopy, and the water surface
- the canopy is a requirement from the boss of house, so going without a canopy is not an option. :)
- these days, with my T5HOs, my water temp ranges from 78 to 80 when the lights are on

I am looking at the HelloLights 250w HQI retrofit kit below:

http://www.hellolights.com/index.asp?PageAction=VIEWPROD&ProdID=1325

I've e-mailed with HelloLights and they say I can mount the lights as low as 4 inches (between the UV shield and the water surface). These lights are 3" tall, and mounting them under my canopy would give me about 5" clearance to the water surface.

So, finally, my question: :) I'm curious about folks that have MHs mounted in a canopy this close to the water. Are you able to maintain your water temp without a chiller, especially during our hot summer months? Do you think my four 80mm PC fans will be enough to cool the canopy so the lights don't heat my water too much?

Worst case, I figure I could go ahead and get the lights and if I find they heat my water too much, sell the lights and go back to my T5s, but figured I'd ask for folks' experiences first!

Thanks!
 
What temp do you keep your house during the Summer?

I think this is one variable that you left out that makes a big difference.

If you keep it 80 degrees in your house I think your tank will get up to 82 or 83.

But if you keep it around 76, I personaly think you will be ok and your tank will raise up to 79 or 80.

That is my personal experince running, SE 250w MH in a canopy close to the water with 4 PC fans blowing in.

Hope that helps,

Matt
 
@Mholton wrote:
What temp do you keep your house during the Summer? I think this is one variable that you left out that makes a big difference. If you keep it 80 degrees in your house I think your tank will get up to 82 or 83. But if you keep it around 76 said:
Thanks, Matt. That's very helpful, especially knowing your current setup is very similar to the one I'm planning.

During the summer, our thermostat is programmed to go up to 80F during the day when no one's home, then down to 77F in the evening. Maybe I could drop the "away" temp down to 79F and still be ok.

Another thing I left out of my original post was that I do have a sump which would probably also help fight the heat.
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I keep my house @ 76° F all the time. my lights are 15" off the surface of the water. The lowest I can keep my temp is 78°. with no chillers and lots of fans. I have 2x120 mm in the Canopy 2x120 mm in the stand and 2x120 mm in the sump! most are 75 cfm except the stand which are 45 cfm .
 
only thing is five inches might get salt spray on the bulbs or glass shield if you go de bulbs...
 
You are going to see a big increase in heat, especially using HQI's. They give off the most heat. Your fans are also a problem... you should have some blowing out. Blowing heat in exclusively accomplishes little other than blowing heat onto the surface. You need some exhaust, powered with a fan. If you can manage it, switch a couple of the existing ones to exit or install those additional ones as exits. The exits can go back against the wall, but I would have the intakes coming from the front or the sides.

The best method to reduce heat, other than a chiller, is to encourage evaporation and unless there is an exit or cooler source of air coming in with an exit, you won't get much.

Same goes for the sump space.. get some fans to the outside of that as well, not just over the sump, but outward as well in the room.
 
I used to have fans in the back of my 55g's canopy, and while they were set to blow air into the canopy, the heat they forced out seemed to loop and blow back in. Having fans on the ends would be better because it will draw in air from the room and not from the heat in the back of the tank.

Having fans blowing straight down would work as well.

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Later I bought fans with blue LEDs which I altered to point down into my reef like moon lighting. http://www.melevsreef.com/pics/0704/moonlight.html

A fan or two blowing down on to the surface of the water in the sump will help as well.

Keeping your home at 80F during the daytime will be quite a test of those fans with MH lighting cooking the water during the day time so close to the surface of the water. Since bulbs are supposed to be 9 to 12" off the water, you have a situation on your hands. If you decide to do this, I suggest you do it on a day that you are home to observe what happens. That includes setting the thermostat to 80F while you are there all day.

Perhaps you can run your lights later in the day, so that by the time you come home and lower the thermostat, that cooler air will assist in cooling the tank during the second half of the photo period, plus you'll get to enjoy your tank during the evening.
 
Another option is to use pendants and mount them on top of the canopy. This is how my 75 is done. I cut 2 square holes just smaller than the pendants and then trimmed out with 1/4 round to hold them in place. A large % of the heat is outside of the canopy.
 
Thanks, everybody. I really appreciate all the feedback. It's nice to hear that I could have some possible options, instead of just "no way I can do this."

KuyaTwo - I agree - I was assuming that cleaning salt from the UV shield will be a weekly chore, if not more frequently, with the lights mounted so close to the water. :) I'm hoping it will be a lot simpler wiping the glass off, than what I'm having to do right now of cleaning my T5 reflectors.

DaveJ - yes, I can definitely rewire the fans so that one side blows out. I actually had it wired this way (blow in on one side, and blow out on the other) when I first put the fans in, but the ends of my T5HOs closer to the "blowing out" side stayed hotter (I could feel the heat from the other side of the top of the canopy) than the side that was "blowing in", so I changed it so that both sides blew in.

Maybe since the back of my canopy is open, the fans that were exhausting were just sucking fresh air in from the back?

I could also add a couple fans in the rear blowing out, but do you think the fans would perform better if the rear wasn't wide open?

Marc - I like the idea of mounting the fans on top blowing down. I especially love the idea of using fans with LEDs! One question though - would there be any danger of the fans melting mounted so close to the lights? In your picture, for example, do the fans survive the heat from your bulbs?

As for my photoperiod, I currently already have my overdriven T5HOs set to come on at 1:30pm, and off at 9:30pm. My A/C switches down to 77 at 6. I could probably delay my photoperiod by an hour to 2:30pm and move up my A/C switching to 77 by an hour to 5, so the lights will really be "uncooled" for 2.5 hours. I like that idea!

Reefmike - I had actually thought about your idea, but mainly as a way to get more distance from the water, buying me an extra 3-4". But as a way to keep the heat out of the canopy, you're right - that's a great idea! Do you really find that a big bulk of the heat radiates from the pendant instead of from the bulb? And another question, do you still have fans in your canopy?

Thanks, again, everybody!
 
Do you really find that a big bulk of the heat radiates from the pendant instead of from the bulb? said:
I would say maybe 40%

And another question said:
I have a deal from Dr. F&S that is 4 little fans in 1 unit. I also have 1 of the Honeywell turbo force fans in the stand. They are controlled by my ACjr.
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Those little blue fans are still with me to this day. They did perfectly fine in all that heat, and I never have ever needed a chiller for any of my tanks in the past 11 years.

Plus those fans are so cheap that if you had to replace them, it doesn't hurt. I think I paid $6 each for them. You'll need to buy a matching power supply to run the fans, so two fans with power supply will run about $20 from Fry's Electronics.
 
I just did what you are planning on doing with a similar setup. I have an Oceanic 90 with their old style canopy. I was running 4 VHO tubes and recently switched out to 2 175W MH moguls and retained 2 VHOs for actinics. I was already running 2 hi-cfm 3.5" fans in a 1 in, 1 out configuration on the back edge of my canopy, 1 on each end.

After adding the MHs, my temp stays a steady 82 degrees. I keep my thermostat on 75 when I'm home and 79 when I'm away. My wife is at home all the time (and doesn't mind being in a 79 degree house :shock: ), so she has sent me the temp at various times over the last week. It is stable, but right on the edge of where I'm comfortable.

I'm planning on adding a sump fan this weekend.
 
Thanks, again, for all the info folks! I will definitely be making this change in a couple weeks after I get back from vacation - don't want to make a somewhat major change like this then go away for a week! :)

I just bought two Aqua-Medic DE pendants from Marcus (djr2001) and will be mounting them in my canopy. The only problem is that the pendants came with magnetic ballasts, so that affects the other part of my concern - my power bill! Oh well. :)

I looked at my canopy a little bit closer this past weekend, and looks like I can raise it about 1.5" by adding some wood where the canopy rests on the top of the tank. I'll let everyone know how it goes!

Thanks!
 
Maybe alter your photoperiod so the lights don't start heating the water until later in the afternoon when the air conditioner goes to it's lower setting?
 
@DheereCrossing wrote:
Maybe alter your photoperiod so the lights don't start heating the water until later in the afternoon when the air conditioner goes to it's lower setting? said:
Yes, I agree. I think that would be a good compromise. Thanks!
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Just to give an update - I installed two Aqua-Medic pendants, each with a 250w DE Phoenix 14000K bulb on the top of my canopy 10 days ago. Since I was concerned the lights would be too close to the water surface if I mounted them on the underside of my canopy top, I decided to mount them on top of my canopy top - cutting holes just big enough for the bottom of the pendants. With this setup, the lights' UV shield is about 7" above the water surface.

Well, after 10 days, and granted, I'm still in my acclimation period and am only running my lights for 6 hours each day (making my way to 8 hours each day), my water temp has been holding steady at 80F. So far so good!

In addition to the lights, I also have one 48" 54w Aquasun T5 and one 48" 54w Pro Color T5. All this with 4 80mm PC fans blowing in 24x7, and not just when the lights are on.

I'm still curious to see what the lights will do to my power bill, but from my calculations they should only add about $20 each month. Hopefully. :)
 
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