Overdriven and HOT!

17 years ago

I just installed some overdriven 4 foot light fixtures (2 bulbs each). They are the standard Shoplights with SL15 ballasts from HD running 2 T8 bulbs.

There are 2 fixtures hanging from each level of a 6' high x 4' wide foot wire rack for a total of 4 fixtures (8 bulbs). They are space 4" above a thermometer and they are hot....I can only touch the bulbs for 5 secs or less so I would estimate the temperature at the surface of the bulb to be around 130F+. I have the long sides of the rack covered with mylar to keep the light out of an ajoining room.

The room temperature is 66, near the rack is 77 and under the lights (4") the tempeature is close to 88.

Is anyone else seeing this? I have some T8 bulbs down int he basement (60F) and they are slightly warm to the touch.

If I need forced air cooling, I may go back to the standard T8 non-overdriven fixtures.

Sort by:Oldest

Comments (5)

shrubs_n_bulbs
17 years ago
Sounds a little on the warm side but the temperature depends on a great many factors. Too hot to touch the tube is not unusual. Even the slightest air movement would cool them noticeably, although just a little air movement may just move the heat from the tubes to your plants, so make sure you have enough ventilation to keep the plants cool too!

As for whether to stick with it, if you need more light and can't fit in more tubes then you'll have to overdrive. Or go to a different format like compact fluorescents or HID. But if you can fit more tubes in then you should probably do that. Overdriving uses more electricity, and produces more heat, than normal fluorescents producing the same amount of light, the only advantage is you need fewer tubes.
maineman
17 years ago
jedijfo1,

I got your email but you didn't show up in the members list at that time (a jedijfo did), so I couldn't send you an email here in The GardenWeb. However, I think it's better to answer here anyway, where answers are subject to "peer review" and suggestions by others.

I think the mylar sheets are the primary cause of your hot running. However, 130Â°F is about normal for an overdriven T8 at the surface. You drink coffee that is much hotter than that. And I seem to recall that a non-overdriven T8 is about 120Â°F on the surface.

As shrubs_n_bulbs suggested, you need some ventilation, particularly in the confined space between the mylar reflecting sheets. I use open chrome wire shelves and I use small electric fans to provide an artificial breeze for my seedlings.

If it's any consolation, your overdriving ballasts are actually running cooler because they are "loafing" driving a single tube instead of a pair.

You might want to re-think the placement of the mylar sheets. Perhaps if you described your layout in more detail, we could suggest a better alternative than your present setup.

MM
Related Discussions
LED Headlights
Q
Comments (24)
I've wanted to upgrade my tractor to LED headlights, but there probably isn't a direct plugin that would work on my mower. That's because my old Wards Signature 2000 headlights are driven off an (approximately) 12vAC winding in the alternator. These headlights get brighter with engine speed, and go off when the engine stops. Since they are incandescents they don't care if it's AC or DC, but LEDs of course would care. I don't actually do that much mowing at night, but when I do use the headlights it's mostly just to finish up some area after sunset. The existing headlight setup on this Wards is susceptable to collecting dirt and dust behind that big wraparound lens up front, which reduces the light output. It will put out a little 'pool' of light on the ground immediately in front of the mower, just enough to barely see where you're mowing, but not always enough to reliably see hazards the grass. Just once I'd like to enjoy some really decent light out there, for those rare occasions I mow in the dark.
...See More
How far away from seedlings with overdrove lights?
Q
Comments (4)
ellieandethansmom, I let my overdriven fixtures come within an inch or two of my seedlings. They aren't awfully hot, so the seedlings can come close. They may grow a bit faster than you are used to, so there is a bit more danger they will grow into actual contact with the bulb and be scorched a little. You may need to shorten your chains a notch about every day in order to maintain a little clearance. MM
...See More
I have found the BEST cheap flourescent ballast/fixture - cont'd.
Q
Comments (150)
A few years ago I needed to increase the light in a kitchen lit by an overhead fluorescent fixture. As I found it, it had two 4-foot T8 735 tubes and an "energy-saving" (read: light-reducing) instant-start ballast. To make it brighter without the hassle and expense of replacing the lamp fixture, I replaced the ballast with the highest-overdriving ballast I could find that could drive a pair of F32 T8's. After some online research, I wound up buying a Philips Advance IOP3P32HL90CSC (a.k.a. IOP3P32HL90CSC3SI , sometimes with several hyphens inserted for readability). It can drive either 2 or 3 bulbs, but overdrives more when used with 2 bulbs. This was a few years ago, there might be something better now, but 1.37 ballast factor replacing a 0.87 or something makes a substantial improvement in brightness. I also upped the brightness slightly by replacing the TL735 bulbs with TL830 or TL835's which are slightly brighter and have better color rendering, which the eye perceives as adding brightness. Re: Philips TL930/TL950 :I've used both the Philips TL930 (95CRI) and TL950 (98CRI) 4-foot tubes., which fortunately I was able to buy two at a time from the local retailer. The TL950s illuminated my kitchen; the 930s went into a basement rec room where they match the color temperature of halogen downlights. The TL950s won't blow you away upon first turning them on - they look like typical cool/sunlight fluorescents at first. Its just that the different colors really pop out well and cleanly and the colors jump out at you rather than being dulled. The kitchen there has no windows, and in the morning sunlight, I noticed the ambient light from the windows across the apartment matched the TL950 light in the kitchen perfectly. If I take pictures with a film camera loaded with standard color film (daylight-balanced), pictures taken with available light indoors under typical "cool white" fluorescents lend an awful greenish cast to everything, but those shot under TL950s had perfect color. That says boatloads about the TL950's color accuracy. As for the lower lumen output, I again compensated by overdriving them by about 25%. I needed a rapid-start ballast for these fixtures, and went with a GE/Motorola ballast that overdrives a pair of F32 T8's with a ballast factor of about 1.20 IIRC, not as bright as the Philips I mentioned above but adequate for my needs here, plus I needed rapid-start rather than instant-start for this application. There are (were?) 2700K, 3500K, 4100K, and 6500K versions of these bulbs sold in Europe. Too bad they aren't sold in North America.
...See More
cause for overdriven fixture failure?
Q
Comments (2)
Be sure that both ballasts have their ground wires attached to the fixture frame with an electrically sound connection. For the second ballast I drill a hole in the frame and scrape the white paint away from the hole to expose bare metal. I then use a pop rivet with matching washers to secure the new ground wire to the frame. Be sure that no bare hot wires can touch the fixture frame. I use crimp connectors, although the screw-on connectors are good enough if you screw them on properly. I'm not sure the problem is with your fixture, however. It could be that the first bulb simply burned out and that the second bulb was defective to start with. The electronic ballasts are sensitive to electrical surges. I protect mine with surge protector plug-in strips. Once I plugged an overdriven fixture directly into a wall socket and the contacts weren't made simultaneously, causing a surge, and the ballast itself was fried. Since then I use surge protectors that have their own on/off rocker switches. MM
...See More
jedijfo1
Original Author
17 years ago
Thanks for the advice. Also have a open wire wire chrome shelf from Lowes. about 6 feet high, 4 feet wide and 18" deep (4 shelves). I use the mylar sheets (actually 1/4" insulated mylar) to do 2 things:

1.Reflect the light back onto the plants
2. Prevent the light from the shelves from blinding us in the family room next door.
The mylar only is on the long (4 foot sides). The bottom, top and sides of the rack are open.

With 2 normal fixtures I get a rise of only about 8-10 degrees. When the room temp is 60, the surface 4 in below is
about 68-70.. Seems alot better and I can touch the bulbs. Before the label on the reflector seems to be melting and caused a stink. I can always open the windows.. Plenty cold outside next to the rack...I hate to use more power. It is expensive here in the northeast
capm
17 years ago
Those SL15 ballasts are also generating plenty of waste heat, and heating the lamp filaments the whole time.

See my post here:

http://forums.gardenweb.com/forums/lights/?28645
capm
17 years ago
Oops!I meant here:
http://forums.gardenweb.com/forums/load/lights/msg0213125528645.html

Overdriven and HOT!

Comments (5)

shrubs_n_bulbs

maineman

Related Discussions

jedijfo1
Original Author

capm

capm

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

Overdriven and HOT!

Comments (5)

shrubs_n_bulbs

maineman

Related Discussions

jedijfo1Original Author

capm

capm

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

jedijfo1
Original Author