overdriven fluorescents - SL15 revisted

17 years ago

My neighbor, who has been lurking on this board for some time, asked me about overdriving lamps with Sunpark SL15 ballasts.

There are better options.

The SL15s are very inefficient and not particularly well built.

Efficiency: The SL15 ballasts have a 50-60% power factor. This means that 40-50% of the power consumed goes to heating up the ballast not to lighting the lamp -- raising the electric bill and heating up the fixture. Decent electronic ballasts have a .98 or better power factor.

Durability: I hung 20+ SL15 based shoplights, for what was supposed to temporary lighting a few years ago. After 16 months I had to start replacing ballasts at the rate of 2-3/yr in a not demanding environment (Price: 2 SL15 shoplights now run about $16 all told at my local HD. Shopping online Tech Consumer Products Inc ballasts run about $14-$15 ea, GE UltraMax run about $16-$17ea.

If IÂm not overdriving a two lamp fixture, for $7 more I can get a really good ballast that uses one-half the power, paying for itself in about 1000hrs.

If I want to overdrive, for the price of two SL15s I can get one really good 4 lamp ballast and use it to overdrive 2 lamps.

Ballast factor:

ÂNormalÂ ballast factor lamps (including the SL15s) have a ballast factor of .88 -- they run a lamp at about 88% output compared with a lab standard and are tuned to maximum efficiency at that point. High ballast factor lamps typically have a ballast factor of 1.15 Â they generate about a third more light than a ÂnormalÂ ballast and are tuned to maximum efficiency at that point.

To moderately overdrive your fixture use a name brand high ballast factor 2 lamp ballast. YouÂll get a third more light and only use 75% as much power compared to using a single SL15. YouÂll also be using a ballast specifically designed for the job.

Using a ÂnormalÂ bf 4 lamp ballast to drive two lamps youÂll get about 40% more light while still using 20% less power than a single SL15.

Using a ÂhighÂ bf 4 lamp ballast to drive two lamps youÂll get almost double the light while using only about 30% more power than a single SL15. (My spec sheet graphs extrapolate to twice the lumens, but you are operating outside the design envelope so I would expect 180% to be a more reasonable guess).

By comparision, using a pair of SL15s gives you about half again as much light, using 1.7 times the power of a single SL15.

For design flexibilty TCPI offers a 4-3-2 ballast you can wire as a normal two-lamp, normal four-lamp, or overdriven two-lamp fixture. (I donÂt think it comes in a high ballast factor model).

Finally, a note on lamp starting:

Rapid start ballasts (such as the SL15) constantly heat the lamp filaments, even after the lamp is lit. This means that about 5% of the power going to the lamp is just converted to waste heat, not lighting the lamp,

Instant start ballasts just heat the filament at starting, hence are more power efficient, at the expense of reduced lamp life (in terms...

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Comments (14)

ccc1
17 years ago
Capm,

On the original thread, the SL15 ballast was not sellected because it was a perticularly good ballast, but rather because HD was having a special for a shop light that contained an SL-15 for $6.49. I believe it later went as low as $4, so there was a lot of activity/hype around this ballast because of it was a good bang for the buck.

At $15, it's not reall that good... Other overdrivable ballasts discussed were:

2-Lamp
======

Sunpark SL-15

Advance REL-2S40-SC
REL-2S40-RH-TP
REL-2p32-SC

GE B232R120HP
B232M20RH

Sylvania QTP 2x32T8/120 RSN-D
QT2x32/120 IS-SC
QTP 2x32T8/120 ISN-D

4-Lamp
======

Advance REL-4P32-SC

GE B432M120RH
432 MAX

Sylvania QT 4x32/120 IS-SC
QTP 4x32T8/120 ISN-A

Fulham Workhourse 5

Damar 3093A
maineman
17 years ago
ccc1,

"At $15, it's not really that good..."

I think Home Depot still charges only about $8 per two-T8 fixture here. So far, after three years of use, I've had only one SL-15 go bad, and that was in a setup without a surge protector. I am now using surge protectors almost exclusively.

As I expand my plant starting activities, I will keep in mind the information given here about better alternatives to the Sunpark SL-15s. However, the Home Depot Commercial ShopLights with the overdrive conversion have performed very well for me in the past years, producing lots of big healthy plants.

MM
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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
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Mark , I meant to try to answer you sooner, but lost track of your post. 1) I saw the SL16 label on a box the last time I went to Home Depot. I had the box opened and saw they had the correct SL15 ballasts in them. I believe that they may be changing the style of the fixture and just used the old number and upped it by one, not realizing that somebody initially based the product number on the ballast number. Beats me. I always open one box to see if its got the SL15. Sunpark doesnÂt make an SL16. 2) The traditional T12 fluorescents were designed to use 430mA each, and use a magnetic ballast. The newer T8Âs have been designed for 265mA of current. The SL15 ballast is able to drive the old F40T12Âs, but it causes the circuitry to operate different, drawing less current than the older design normally would use. I use F40T12Âs in them, both out-of-the-box and overdriven. An overdriven fixture really lights up the older style 430mA tubes. (Extra design info: T12HO=800mA , T12VHO=1200mA, 34wT12=460mA, 20wT12=380mA, 20w/40w slimline=425mA, and thereÂs more, each different T5 wattage has a different current design.) 3) Probably not. It is nearly always cheaper to buy a good, inexpensive shoplight and remove the ballast Especially that Home Depot one. 3b) I donÂt know. I had downloaded brochures on them from GE months ago. They may be designed differently, as they are supposed to have special features, such as automatic line voltage matching. 4) I donÂt know the fixture you speak of, but reflecting back light that otherwise would escape is always a good thing. 5) Power Factor (not ballast factor) is a ratio of the how efficiently the current and voltage waveforms match due to the circuit design. Without trying to remember how to explain it, I can tell you this Â donÂt worry. Poor Power Factor normally does not cost you. It costs the electric company, unless they have special meters on your house to detect it. That is rare. 7) DonÂt try to switch in and out of overdrive. Too late for details, but youÂre asking for trouble if you do it If you are using a single SL15 to light each bulb, then put any switches on the line-side/power-side of the ballasts (black wire). Zink
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overdriving t8s would be more economical Don't rely on it! I've said this before, and I suspect I'll have to say it many times again, but the largest cost in plant lighting is the electricity, so it makes sense to look for the most efficient solution without paying huge money. Plan on $5/month for 4 overdriven 17W tubes, so several hundred dollars by the time you are replacing the tubes. I estimate you'll be getting around 70 lumens/watt from overdriven F17T8s, barely more than a spiral compact fluorescent and considerably worse than a 2' compact fluorescent like the 55W models. Personally I think that 2' tubes are generally a poor choice in efficiency terms and you'd be better off looking at whatever compact fluorescent will fit your small space. Of course $150 for a 2' fluorescent fitting is a lot of money and you are unlikely to save that much on electricity no matter what lights you use, especially as replacement tubes are about $10. Maybe they'll be cheaper by the time they need replacing ;) It is worth noting that 4' T8 tubes produce more light per watt than 2' T5HO tubes, as always overdriving (which is all the high output means) and short tubes reduce the efficiency. Longer tubes are better and the 54W 4' T5HOs are as efficient as the standard 4' T8s, an 8' T8 is more efficient than either, and the 28W standard T5s are more efficient still.
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Wow, thanks Kimberly for reviving this old thread. Because I have learned some things in the meantime. (Automotive HID lights tend to be more expensive, compared to what's available elsewhere). I repeat my warning to not use the Philips retro-hps bulbs (the CDM400S51/HOR/4K/ALTO; the GE equivalent is CMH400/U/830/R) on the GE Ultra-max e-ballast. Also do not use these on any high or very high frequency e-ballast. There is a CMH bulb designed for use with low-frequency e-ballasts like the GE Ultra-max; the SPXX. However at present is available only in vertical orientation (horizontal is recommended for various reasons). Ceramic arc tubes (like those in HPS and retro-hps CMH) were designed for use with magnetic ballasts and have a stable arc stream in that case. However if subjected to high frequency electronic ballasts the arc stream is unstable and this heat-stresses the bulb. This explains Shrubs' comment that electronic ballasts run the bulbs hotter. This is not just because some (like Lumatec) slightly over-wattage at 1050w. The instability in the arc stream heat-stresses the ceramic elements, causing premature failure and leakage of heavy metals including mercury. Eye Hortilux is the premier manufacturer of conventional horticultural lighting. They published an article in the October issue of Maximum Yield magazine. They point out, HPS and MH bulbs are not suited to high-frequency e-ballasts (with frequencies between 30,000 and 45,000 cycle per second). Which explains the high failure rate and increasing number of lawsuits. For the article, go to maximumyield.com and click unto "Download MY". Then scroll down to the third section of October 2008. Notice, old-style MH are also not compatible with e-ballasts. Even though they are not using the glued ceramic arc tube, the quartz can still rupture and in any event the instability creates a heat stress (shortening bulb life). Sun-Pulse bulbs are designed to have stable arc stream with e-ballasts tuned to them. Sun-Pulse are the only PSMH bulbs designed specifically for e-ballasts. Lumatec, Galaxy, and GE are the only e-ballasts that have been tuned to the Sun-Pulse bulb. There is an electronic e-ballast that is very high frequency (about 300,000 cps) but they go only to 600w and are not readily or cheaply available. As I pointed out in previous posts, this very high frequency is desirable for plant growth because it is closer to natural sunlight. However CMH requires a specific type of low frequency e-ballast (or magnetic ballast). Not all low frequency e-ballasts are compatible with all CMH. PSMH can use either low or high or very high frequency. Because CMH uses ceramic arc tube (which is glued together) it is inherently unstable at high frequency or high wattage. Sun-Pulse are a type of PSMH that are designed specifically for e-ballasts. I recommend the Sun Pulse bulbs over CMH, however they cost more. So for those who cannot afford, use magnetic ballast with CMH. Use the 10K Sun-Pulse for veg, the 3K or 4K for bloom. The Sun-Pulse are even more full-spectrum than CMH. A 400w Sun-Pulse (or cmh) produces far more intensity than can realistically be achieved with fluorescents. The high intensity should be moved quickly in a circle, to cool the bulbs and distribute the light evenly. If this is not feasible (for lack of space or money), combine several 400w bulbs in a cluster and overlap their fringe areas. This simulates how the points in linear fluorescents overlap fringe areas (a 4' line fluorescent tube has an infinite number of points and increasing the number of tubes creates overlapping in more directions).
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shrubs_n_bulbs
17 years ago
Hi Capm,

I'm sure the SL15 is not especially high quality, but much of the technical information in your message is incorrect or misleading. Power factor is irrelevant to 99% of us since we are not charged for the "lost" electricity, the power company bites that bullet. And your discussions of efficiency and ballast factor are misleading. High ballast factors mean more light but not higher efficiency, in fact usually lower efficiency. This is particularly relevant when overdriving; an overdriven tube is almost always beyond its peak efficiency and the higher the ballast factor you are using, the further beyond that peak it goes. So all your calculations that the higher quality ballast will save you money are simply wrong, there will be almost no difference in running costs from the el cheapo SL15. Unless you have to buy a new one every six months ;)

The descriptions of the various starting types are correct, although the filament heating is less than 5%, at least on the size of tubes we are talking about.

The use of high ballast factor lamps to "moderately overdrive" is of course correct since that is exactly what high ballast factor ballasts are intended to do. Particularly with T8 tubes, this level of overdriving may even operate the tube more efficiently since US T8s are considerably under-driven at standard output, even more so on a 0.88 ballast. European T8 ballast drive a little higher straight out of the box, and 2x US T8s are still not far beyond maximum efficiency.

And a very good tip for most growers, overdriving or not, is to get 4-lamp ballasts. They cost hardly more than a single lamp ballast, in fact mine cost exactly the same. Almost all of us need at least four tubes, or two overdriven.
ccc1
17 years ago
I envy you guys that can get the shop light for $8 or less. My local HD here in Toronto is still selling it for CAD $15 which is about USD $12.50. Even then, when I bought the light, the ballast inside was not the overdrivable SL15. Seems to be more difficult to get a cheap, overdrivable electronic ballasts here in Canada. =(
shrubs_n_bulbs
17 years ago
Same here. Electronic ballasts start at about fifteen pounds here, $25-$30 US. Magnetic ballasts are less than half that, but they are so useless to man and beast that they should be outlawed ;)
jedijfo1
17 years ago
Couple of points:
Does anyone recommend a good 4 light fixture and good ballast that would compare pricewise with 2 HD fixtures (at about $16).

Also, the SL15 has a harmonic distortion of 130% which messes up my home automation x10 signals. I had to get a filter to make it work again.
capm
Original Author
17 years ago
"At $15, it's not really that good..."

The SL15 is only about $8, my point is that for about the same price as two SL15s (to overdrive 2 lamps) you can get one good 4 lamp ballast (also to overdrive 2 lamps).

shrubs-n-bulbs -

"Power factor is irrelevant to 99% of us since we are not charged for the "lost" electricity, the power company bites that bullet."

As I think about it, you should be right. But it doesn't agree with my observed power consumption.
Apparently the low pf ballast is not as efficient as the high pf ballast. (Or the SL15 is not as efficient as the GE ballast).

I have a string of 8 SL15 shoplights (16 lamps). It consumes about .7kw. I also have a mixed string of 4 SL15s and 4 TCPIs (16 lamps). It consumes about .525kw. And a string of 5 4-lamp TCPIs/GEs (20 lamps). About .5kw. I assumed (without thinking much about it) that the difference in efficiency was related to the difference in power factor.

This also suggests that I overstated the savings by a factor of about two.

But I am observing a difference in running costs.

Regarding the filament heating with a rapid start ballast - I was reading a spec sheet that said 2 watts for the filament. On a 32 watt lamp that would be over 5%. Even if it were 2 watts/ballast (1 watt/lamp) it would be 3%.

I was not trying to mislead in my discussion of ballast factor. Overdriving is certainly less efficient (lumens/watt) than not.
But if you are going to overdrive, I would do it with the most efficient ballast I could find.
And I would rather use one efficient (4 lamp) ballast than two cheapo inefficient ballasts that cost just as much initially and more to run.

I agree with you about moderately overdriving with a high bf ballast. On one T8 lamp curve (and I know they do vary a bit) I read max lumens/watt at slightly over 1.0 bf. That suggests to me that a typical high bf of 1.15 is probably not a whole lot less efficient than a normal bf of 0.88.

So, unless I'm missing something, here's what I'm seeing:

Compared to a single SL15 driving two lamps-
A good 1.15 bf ballast should give more lumens and more lumens/watt at a slightly higher initial cost and comparable running costs (though obviously higher running costs than a good .88 bf ballast)

Compared to two SL15s driving two lamps -
For the same initial cost, get a good 4 lamp ballast.
It'll be more efficent and last longer.

(of course this ignores the initial cost of the fixture - that's where the HD shoplight may have an edge)

Thanks for the response!
shrubs_n_bulbs
17 years ago
You might find it interesting to watch how fast the various ballasts make your electricity meter spin. If you have a simple watt meter, then you will find that the low power factor ballast is apparently consuming more power. This is because most wattmeters just multiply together the mean current and the mean voltage. Your utility company meter actually measures the instantaneous product of current and voltage and the low power factor ballast should read about the same as the high power factor ballast. Because the current and voltage are varying out of phase in a low power factor device, the true power consumption is lower than the apparent power consumption shown on your wattmeter. Low power factor devices don't actually consume more power in watts but they do place a higher load on the wiring and some utility companies will charge for this, mainly to high load customers.

The US 1.15 ballast factor is close to the nominal level for European spec T8s. They are rated at 36W and around 3300 lumens. Ballast factors higher than 1.0 are uncommon in Europe since lifetime and efficiency start to drop off when you get much past these levels.
capm
Original Author
17 years ago
shrubs-n-bulbs -

Can't see much with a digital utility co. meter, unfortunately.
I'll check with the owner of the power meter used to measure power consumption. It was measuring kW, not kVA, so the measured difference in power consumption between the lighting circuits should be real. It is possible I've been embarassingly misled.

If so, I will certainly feel much better about continuing to use my existing SL15s until they fail. Although after the last one failed in a (literal) cloud of smoke I've been considering replacing them all anyway.

I'm still confident that rather than buying extra fixtures just to scavenge their their (cheap 2-lamp) ballasts, it is better to get good 4-lamp ballasts for overdriving, especially when the cost is comparable.
aes123
17 years ago
I can't comment on the electrical portion of this thread, but for me, part of the benefit of using the cheap HD fixtures is getting a fixture, even if it's not so great. While I'm sure there are vastly superior ballasts available, I'd then have buy materials to build a fixture.

For those of you in regions where the SL15 is either unavailable, or more expensive, I recently noticed that Sunpark sells the ballast for US$6.50 on its website...
maineman
17 years ago
aes123,

This might be the Sunpark SL15 listing.

MM
trant
17 years ago
Yeah I jumped aboard back 2 or 3 years ago when those Home Depot Sunpark fixtures were going for about $7 each, for ballast + housing. So it seemed to be a decent deal.

I have purchased probably 16 of them to give me 8 overdriven 2-bulb fixtures.

I had one of those ballasts just suddenly not work since then, so it's not that bad of a record.

I do plan on upgrading next year or maybe even sample some new equipment this year in preparation for next year. I am very interesting in getting those GE Ultra High 4 bulb ballasts though, sounds like alot of output. I could easily grow lettuce full cycle indoors with that.
trant
17 years ago
Hey I was shopping around for one of those 4 ballast GE ultra max ballasts and I find it costs a whopping $55.

This is the one you were referring to, right?

http://jandslighting.com/catalog/product_info.php?cPath=50_346_311&products_id=1890
bobntess
17 years ago
I found some ballasts that may be good for overdriving.
They are Advance Intellivolt #ICN-4P32-SC
120 - 277v, instant start, electronic ballast.
4 lamp, F 32, T8.
Does anyone know if these would be suitable for overdriving a 48", 2 lamp fixture?

overdriven fluorescents - SL15 revisted

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