150w MH a few inches from acrylic? Safe or Meltdown?

reef_economist · 07/28/2006, 04:51 PM

I want to use a SunPod on legs over an acrylic tank. Should I be concerned about the lights that close to the acrylic?

nemo g · 07/28/2006, 05:18 PM

if you are talking plastic just under the light, i think you know the answer to this already.

which is why every halide fixture ive encountered has a glass shield if it has one at all. and they are just a few inches from the bulb.

however, if its the tank itself, the light really shouldnt be that close to the panes, and what heat does get to it, should be transferred to the water esentially cooling the acrylic.

try it and see how hot the acrylic gets. remember to do the touch test just before you are going to turn the lights off, as well as throughout the day. this way you get a good idea if the heat accumulates or not during the day.

reef_economist · 07/28/2006, 05:35 PM

Quote:

however, if its the tank itself, the light really shouldnt be that close to the panes

I'm concerned about the bracing. I've seen people successfully using SunPods and similar legged fixtures over acrylic, but not with bracing on top..

I probably wouldn't think twice about it if it was 300w of CF in a similar fan-cooled fixture.. I'm just concerned over the intensity of the MH bulbs radiating that wattage across a smaller area..

Peter Eichler · 07/28/2006, 09:54 PM

Quote:

Originally posted by nemo g
if you are talking plastic just under the light, i think you know the answer to this already.

which is why every halide fixture ive encountered has a glass shield if it has one at all. and they are just a few inches from the bulb.

however, if its the tank itself, the light really shouldnt be that close to the panes, and what heat does get to it, should be transferred to the water esentially cooling the acrylic.

try it and see how hot the acrylic gets. remember to do the touch test just before you are going to turn the lights off, as well as throughout the day. this way you get a good idea if the heat accumulates or not during the day.

All the old Coralife and Hamilton SE MH fixtures used to have acrylic UV shields. How the heat output of the HQI bulbs compares to the old 175w bulbs I'm not sure though.

nemo g · 07/28/2006, 11:38 PM

wow, talk about design flaw. ive read on here of stories of center braces melting due to being directly under a halide bulb.

i wonder if "old" fixtures means they fixed that issue. just doesnt make sense to risk it when glass is perfect for the job.

The Grim Reefer · 07/28/2006, 11:55 PM

If you are talking a 150 watt fixture with the UV sheild a few inches above acrylic it shouldn't be an issue.

reef_economist · 07/30/2006, 05:27 AM

Thank you for the feedback everyone.

I thought up an experiment. I remembered that I have a 2 x 150W halogen motion light. I know it's different technology, but I figure wattage dissipation should be close. The bulbs are contained in a reflector assembly smaller than I would assume the reflector area of the SunPod to be and they are shielded by glass.

I held my hand up at the distance I thought the tank would be from the light. It was hot, but not more than I would expect the acrylic to be able to handle. *edit: plus the SunPod is fan-cooled, while the motion light is not*

I will try to take a temperature reading and compare that with rated values for acrylic.

xtm · 07/30/2006, 09:16 AM

I have a Hamilton 175w halide shining directly on top of my acrylic center brace.. the acrylic brace and the halide are about 5 inches apart. I've had it set up this way for about 2 years and the acrylic is not affected at all. It's not even very warm to the touch after all day of halide exposure.

You should be fine.

skylar · 07/30/2006, 07:12 PM

Ask the owner of Aquarium Concepts in Hayward and he'll tell you different. A 400w busted his 1.5 " top on a huge display tank. Tru Vu also recommends the arc of the Halide bulb is over water -

I also read a post on RC long ago where a guy had a 250 or 400 over his center brace for a couple of years and then - CRACK - water hit it and it snapped. Good luck

Also the experiment with the motion light. They won't get nearly as hot as halides due to the fact the light is not as focused from one point in the bulb. Same watts not the same intensity.

07/28/2006, 04:51 PM	#1
reef_economist Registered Member Join Date: Jul 2006 Posts: 6	150w MH a few inches from acrylic? Safe or Meltdown? I want to use a SunPod on legs over an acrylic tank. Should I be concerned about the lights that close to the acrylic?

07/28/2006, 05:18 PM	#2
nemo g Registered Member Join Date: Feb 2006 Location: west side iz da best Posts: 1,039	if you are talking plastic just under the light, i think you know the answer to this already. which is why every halide fixture ive encountered has a glass shield if it has one at all. and they are just a few inches from the bulb. however, if its the tank itself, the light really shouldnt be that close to the panes, and what heat does get to it, should be transferred to the water esentially cooling the acrylic. try it and see how hot the acrylic gets. remember to do the touch test just before you are going to turn the lights off, as well as throughout the day. this way you get a good idea if the heat accumulates or not during the day. __________________ nG Current Tank Info: tis da bestest tank eva

07/28/2006, 11:38 PM	#5
nemo g Registered Member Join Date: Feb 2006 Location: west side iz da best Posts: 1,039	wow, talk about design flaw. ive read on here of stories of center braces melting due to being directly under a halide bulb. i wonder if "old" fixtures means they fixed that issue. just doesnt make sense to risk it when glass is perfect for the job. __________________ nG Current Tank Info: tis da bestest tank eva

07/28/2006, 11:55 PM	#6
The Grim Reefer Ready for some NOBALL!!! Join Date: Sep 2003 Location: Kingman Az Posts: 25,259	If you are talking a 150 watt fixture with the UV sheild a few inches above acrylic it shouldn't be an issue. __________________ America, the way it outta be! Current Tank Info: 120 Starphire with Illudium Q-288 Photon Regurgitator DIY LED lighting

07/30/2006, 09:16 AM	#8
xtm Registered Member Join Date: Jan 2005 Location: Panorama City, CA Posts: 4,703	I have a Hamilton 175w halide shining directly on top of my acrylic center brace.. the acrylic brace and the halide are about 5 inches apart. I've had it set up this way for about 2 years and the acrylic is not affected at all. It's not even very warm to the touch after all day of halide exposure. You should be fine. __________________ Function before fashion Current Tank Info: 120g SPS Tank (48x24x24)

07/30/2006, 05:27 AM	#7
reef_economist Registered Member Join Date: Jul 2006 Posts: 6	Thank you for the feedback everyone. I thought up an experiment. I remembered that I have a 2 x 150W halogen motion light. I know it's different technology, but I figure wattage dissipation should be close. The bulbs are contained in a reflector assembly smaller than I would assume the reflector area of the SunPod to be and they are shielded by glass. I held my hand up at the distance I thought the tank would be from the light. It was hot, but not more than I would expect the acrylic to be able to handle. edit: plus the SunPod is fan-cooled, while the motion light is not I will try to take a temperature reading and compare that with rated values for acrylic.

07/30/2006, 07:12 PM	#9
skylar Registered Member Join Date: Oct 2004 Posts: 158	Ask the owner of Aquarium Concepts in Hayward and he'll tell you different. A 400w busted his 1.5 " top on a huge display tank. Tru Vu also recommends the arc of the Halide bulb is over water - I also read a post on RC long ago where a guy had a 250 or 400 over his center brace for a couple of years and then - CRACK - water hit it and it snapped. Good luck Also the experiment with the motion light. They won't get nearly as hot as halides due to the fact the light is not as focused from one point in the bulb. Same watts not the same intensity. __________________ Addicted 14 years. Current tank:300g Reef w/ lot's of fish, SPS, LPS, and Clams. 4 x 400w MH 4 x 110 VHO actinic. MTC Ca reactor ER 12-1 & ASMG4Xrc.