MH lighting safety

HybridFish · 02/13/2006, 06:19 PM

Hello all,

I just installed a new 175W MH retrofit into my system and I'm wondering about UV radiation of these beasts. I've noticed that a lot of MH fixtures and pendants have an extra piece of UV blocking glass in front of the bulb for extra precautions. I'm wondering if I should do the same for the retrofit. I understand that the MH bulb's outer coating should block the shortwave UV light (which can cause burns and other nasty stuff). But what about the rest of the UV? This aquarium is going into the family room where we spend a lot of time...

Bottom line... should I worry about UV shielding the MH light by adding a piece of UV shielding glass in front of it?

sales weasel · 02/13/2006, 09:12 PM

That's a question I'd like to know the answer to as well.

tjay · 02/13/2006, 09:17 PM

is this DE or SE bulbs
SE bulbs do not require extra shielding DE do

blgreef · 02/14/2006, 08:29 AM

Most halide bulbs are designed to be run in an enclosed unit, for DE bulbs this is very important due to thehigh UV output. SE bulbs are designed for enclosed units also. Very few halide bulbs are rated for open units by their manufacturer.

Yes reefers run them SE in open units but the following needs to be considered.

If the outer glass is damaged, cracked then the bulb may still run there is now the risk of UV exposure, bad for the tank and even worse for yourself, specificaly towards eye damage.

The inner ARC tube runs at very high temps and pressures, failure of the arc tube can be explosive and the outer envelope on most bulbs is not designed to retain the pieces as such the outer envelope can also fail and you now have a very real fire risk

You may find that most comercial units have the glass to ensure that they fit with the manufacturers recommendations. if you are building yourself then its a choice of risk.

I think outer envelopes getting cracked does happen and arc tube failure seems rare again can happen, as to UV only way to be sure is to shield or check out the spectral plot for the bulb you want to see at what level it output UV.

But most peeps on this board run SE without shield glass.

HybridFish · 02/14/2006, 10:24 AM

It's a mogul base bulb (SE). I understand the (DE) HQI double ended bulbs don't have the shielding built in which is why they NEED the UV shielding glass in front of them.

As for manufacturer specifications... I've called several aquatic bulb destributors like HAMILTON to get any safety reccommendations from the manufacturer but they were unable to get them. They keep the manufacturer private!!! geez... bad enough they don't know anything about them... A question I asked is what type of material they were using to shield the UV and they answered ACRYLIC. This is funny because acrylic OP-3 has an operating temperature of 120 degrees which is way lower than the radiated heat from a MH bulb. Let's also remember that acrylic is a combustable plastic. So I asked the question of what type of exactly what type of acrylic are they using so I could replicate their precautions and they couldn't give me an answer. They don't even know if their bulbs are the type that fizzle out in the case that the outer shell is cracked or broken for the extended time of about 15 minutes... kinda scarry that these people don't know anything about their product.

jlx4 · 02/14/2006, 12:02 PM

Based on past experience, I wouldn't think of running MH without some kind of enclosure. It's only happened once, but I had a bulb explode and the hot glass fragments are still melted into the plastic shield on that end of the hood.

TANGBOY5000 · 02/14/2006, 12:33 PM

I never had any UV problems while running SE bulbs. Now DE are a different story. I got a sun burn from working at the end of the tank where the light spilled out through the vent opening. On most DE fixtures the glass protects the tank from UV, but the sides are open for venting or a fan.

HybridFish · 02/14/2006, 02:19 PM

Quote:

Originally posted by jlx4
Based on past experience, I wouldn't think of running MH without some kind of enclosure. It's only happened once, but I had a bulb explode and the hot glass fragments are still melted into the plastic shield on that end of the hood.

What kind of plastic shield was used?

blgreef · 02/14/2006, 02:20 PM

http://www.ushio.com/Files/Aqualite.pdf

not the bulbs you use but some info, best bet may be to have a search on the NET for details on glass safety etc, general response you will get on the board is run them open should be ok.

And I would think in general this may be true aslong as the bulb does not fail, but this may also be bulb dependant!

the acrylic would give more light transmission if it did not melt, the link above mentions toughened safety glass, may be wirth a look also at some bulb manufacturer, BLV, Ushio osram, phillips etc and check out their tech doc

jlx4 · 02/14/2006, 02:55 PM

I have an old Corallife 6' Hood with 3-175watt MH and two 40 Watt actinic. Has to be at least 15-16 years old, I think it is an acrylic\lexan of some type.

TANGBOY5000 · 02/14/2006, 03:38 PM

All of the old Coralife and ESU hoods had a simple acrylic shield. It was to keep water from hitting the bulbs more than anything else. The fans keep the internal temp just cool enough to keep the acrylic from melting, but if you touch the shield after a couple of hours of operation it sometimes feels tacky.

02/13/2006, 06:19 PM	#1
HybridFish Registered Member Join Date: Oct 2005 Location: San Jose, CA Posts: 287	MH lighting safety Hello all, I just installed a new 175W MH retrofit into my system and I'm wondering about UV radiation of these beasts. I've noticed that a lot of MH fixtures and pendants have an extra piece of UV blocking glass in front of the bulb for extra precautions. I'm wondering if I should do the same for the retrofit. I understand that the MH bulb's outer coating should block the shortwave UV light (which can cause burns and other nasty stuff). But what about the rest of the UV? This aquarium is going into the family room where we spend a lot of time... Bottom line... should I worry about UV shielding the MH light by adding a piece of UV shielding glass in front of it?

02/13/2006, 09:17 PM	#3
tjay Premium Member Join Date: May 2005 Location: Dallas Posts: 759	is this DE or SE bulbs SE bulbs do not require extra shielding DE do __________________ Click the red house for our pictures Current Tank Info: 90 gallon Oceanic RR SEIO 1100 G3 Skimmer, Ozone, 30 gallon sump/fuge, 130 lbs rock, 3 inch live sand bed. 2X250 MH 20K 4X54 Watt T5 actinic:::: 54 gallon corner seahorse tank

02/14/2006, 12:02 PM	#6
jlx4 Registered Member Join Date: Jan 2005 Location: Columbia, Md. Posts: 27	Based on past experience, I wouldn't think of running MH without some kind of enclosure. It's only happened once, but I had a bulb explode and the hot glass fragments are still melted into the plastic shield on that end of the hood. __________________ Jon Current Tank Info: 180 gal. reef

02/14/2006, 02:55 PM	#10
jlx4 Registered Member Join Date: Jan 2005 Location: Columbia, Md. Posts: 27	I have an old Corallife 6' Hood with 3-175watt MH and two 40 Watt actinic. Has to be at least 15-16 years old, I think it is an acrylic\lexan of some type. __________________ Jon Current Tank Info: 180 gal. reef

02/13/2006, 09:12 PM	#2
sales weasel Registered Member Join Date: May 2005 Location: Atlanta burbs Posts: 646	That's a question I'd like to know the answer to as well.

02/14/2006, 08:29 AM	#4
blgreef Registered Member Join Date: Oct 2002 Location: Belgium Europe Posts: 526	Most halide bulbs are designed to be run in an enclosed unit, for DE bulbs this is very important due to thehigh UV output. SE bulbs are designed for enclosed units also. Very few halide bulbs are rated for open units by their manufacturer. Yes reefers run them SE in open units but the following needs to be considered. If the outer glass is damaged, cracked then the bulb may still run there is now the risk of UV exposure, bad for the tank and even worse for yourself, specificaly towards eye damage. The inner ARC tube runs at very high temps and pressures, failure of the arc tube can be explosive and the outer envelope on most bulbs is not designed to retain the pieces as such the outer envelope can also fail and you now have a very real fire risk You may find that most comercial units have the glass to ensure that they fit with the manufacturers recommendations. if you are building yourself then its a choice of risk. I think outer envelopes getting cracked does happen and arc tube failure seems rare again can happen, as to UV only way to be sure is to shield or check out the spectral plot for the bulb you want to see at what level it output UV. But most peeps on this board run SE without shield glass.

02/14/2006, 10:24 AM	#5
HybridFish Registered Member Join Date: Oct 2005 Location: San Jose, CA Posts: 287	It's a mogul base bulb (SE). I understand the (DE) HQI double ended bulbs don't have the shielding built in which is why they NEED the UV shielding glass in front of them. As for manufacturer specifications... I've called several aquatic bulb destributors like HAMILTON to get any safety reccommendations from the manufacturer but they were unable to get them. They keep the manufacturer private!!! geez... bad enough they don't know anything about them... A question I asked is what type of material they were using to shield the UV and they answered ACRYLIC. This is funny because acrylic OP-3 has an operating temperature of 120 degrees which is way lower than the radiated heat from a MH bulb. Let's also remember that acrylic is a combustable plastic. So I asked the question of what type of exactly what type of acrylic are they using so I could replicate their precautions and they couldn't give me an answer. They don't even know if their bulbs are the type that fizzle out in the case that the outer shell is cracked or broken for the extended time of about 15 minutes... kinda scarry that these people don't know anything about their product.

02/14/2006, 12:33 PM	#7
TANGBOY5000 Premium Member Join Date: Sep 2003 Location: Cincinnati Posts: 2,130	I never had any UV problems while running SE bulbs. Now DE are a different story. I got a sun burn from working at the end of the tank where the light spilled out through the vent opening. On most DE fixtures the glass protects the tank from UV, but the sides are open for venting or a fan.

02/14/2006, 02:20 PM	#9
blgreef Registered Member Join Date: Oct 2002 Location: Belgium Europe Posts: 526	http://www.ushio.com/Files/Aqualite.pdf not the bulbs you use but some info, best bet may be to have a search on the NET for details on glass safety etc, general response you will get on the board is run them open should be ok. And I would think in general this may be true aslong as the bulb does not fail, but this may also be bulb dependant! the acrylic would give more light transmission if it did not melt, the link above mentions toughened safety glass, may be wirth a look also at some bulb manufacturer, BLV, Ushio osram, phillips etc and check out their tech doc

02/14/2006, 03:38 PM	#11
TANGBOY5000 Premium Member Join Date: Sep 2003 Location: Cincinnati Posts: 2,130	All of the old Coralife and ESU hoods had a simple acrylic shield. It was to keep water from hitting the bulbs more than anything else. The fans keep the internal temp just cool enough to keep the acrylic from melting, but if you touch the shield after a couple of hours of operation it sometimes feels tacky.