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The F64: Powering a bulb at 20w or 40w using one ballast and one wire.
I get a lot of funny looks when I tell people how we do some of our wiring. Even by engineers, who have strict training in doing things "The Right Way®" and often don't experiment and test ideas that are outside of the box. The focus of this article is on using F40T12 bulbs (4 foot long, 1.5 inch in diameter, like the SG-1-40 and Flower Power) and using an off the shelf F32 ballast.

We have a couple of different 4 foot foot fixtures, but they do share a couple of common traits: They are universal voltage (connect to anything from 120 volt to 240 volt and they will figure it out without you doing anything extra), and they both use ballasts designed for TWO F32 bulbs. They leave our building with the power connected to just one of the leads, and the extra lamp wire capped off.

First, you need to understand the difference in all these F numbers.

F32 is the standard for a bulb that is 48" long (including pins) and is 1 inch in diameter. F40 is the standard for a bulb that is 48" long (including pins) and is 1.5 inch in diameter. Theoretically, you power an F32 with 32 watts of power and you power an F40 with 40 watts. Like all fluorescent bulbs, these can actually run on a range of wattages, and newer ballast designs mean the average F32 is actually powered with 20 to 24 watts instead of 32, as the new ballasts are more efficient. MOST F32 fixtures will let you install the fatter F40 bulb, but some are very slimline and don't have enough room. The lamp holders are just too short. All our fixtures will fit either.

While I'm on the subject, you hear about T5, T8 and T12, but most don't know what that means. It is quite simple. Think of T as "thickness", in 1/8th inch increments. A T5 is 5/8th" in diameter. A T8 is 8/8ths (1 inch) and a T12 is 12/8th (1.5"). The higher the T number, the larger around the tube is.

When we power a Flower Power bulb with one side of a F32 ballast, we are under-powering it on purpose. The phosphor blend is so strong in these lamps, we can get away with running the normally 40 watt bulb at 20-24 watts. In fact, they are engineered specifically for this application, as F32 ballasts are very common, inexpensive and durable, while F40 ballasts are getting hard to find.

Also note that we use "instant start" ballasts, not "program start". Program start ballasts require 4 wires for each lamp. Instant start ballasts require two wires for each lamp. Normally, you will have two blue wires on the ballast, one per bulb. You also have one yellow (or red) wire that the other side of the bulb will share: it is chained from one bulb to the other, like a neutral wire. The instant start ballasts are much simpler to wire and deal with, but are a bit rougher on the bulb. Since our bulbs are certified for 100 watts and can probably handle twice that, this really isn't a problem for our lamps. The type of ballast doesn't really affect the lamp life here.

In addition, we use "shunted" lamp holders in all our fixtures. This means that the two pins are jumped together inside the lamp holder. It doesn't matter which pin you use, both will get the same power at the light bulb. You can tell if a lamp holder is shunted or not by the number of wire holes on the bottom of it. If it has 4 holes, then it is not shunted and it is designed for program start or magnetic ballasts. If the holders only have two holes, they are paralleled as the pins are shunted inside the holder. You can "convert" a non-shunted holder to shunted by jumping across the two pins with a small piece of wire, but it is usually better to just use the right lamp holder to begin with. This diagram shows you how to shunt a non-shunted holder. Note: if you do not shunt the pins and use an instant start ballast, you can actually hurt lamp life because you are powering on only one pin, so use the right holder or shunt it yourself.



In order to (almost) double the power going to the bulb, you would take the extra blue wire and connect it to the lamp holder than already has a blue wire. In some of our fixtures, there is a wire nut on the wire, so you just remove it, and stab it in the 2nd hole in that lamp holder. Other fixtures have the wire pushed into a wire join, so you will need a piece of wire (measure, but likely a foot long) that is SOLID and 18 gauge. Strip it, stick one end in the wire join with the other blue wire, and the other end into the lamp holder. That is all.

You won't be able to install a standard togle switch to change modes back and forth. Trust me, I've tried, but the starting voltage on these ballasts is 600v and most switches have a maximum of 250v capability. I've smoked a bunch of switches to confirm this. If you can find something that can handle 600v, then of course you can try it, but we don't support it because we didn't supply the part.

Why would you WANT to run at double power, you ask? Most people won't. Fortunately, it costs about the same for a two lamp ballast as a single lamp ballast, so it doesn't raise the price of the fixture to have this feature. There are some applications that it can save you money, however.

Most smaller growers are just going to use two of the fixtures for every 1000w hood they are running. They cover an area up to 2 metre x 2 metre (6ft x 6ft). The average distance to the canopy is around 46cm-61cm (18-24 inches) for these grows. Larger growers, however, may run up to 2 metres away from the canopy. Because the bulbs are so far away, they are weaker, but they cover a larger area, twice the size. You can then double the power, using half as many light fixtures and save in start up costs. Keep in mind, if you double the power, you cut the life in half. You get the same amount of UV, you just use it up quicker, so you will be changing bulbs every other flowering season.

Flower Power bulbs are so strong, we really don't worry about power. If anything, they are too powerful. What we concentrate on is COVERAGE: Making sure you have enough fixtures that every plant is getting plenty of coverage. Then you can adjust the "power" by how many hours a day you run the lamps. Normally, 2 to 4 hours is enough, but with half the fixtures and double the power, you may run up to 6 hours a day. Of course, this is all strain dependent, as indica plants can tolerate up to twice the UV of sativa dominant strains, and every strain is different, so you have to (carefully) experiment a bit.

Another group of users who always add this 2nd wire....violin makers. They use our SG-1-40 bulbs, and we do the wiring for them, and they are shipped out at 40w each. They need the extra power to age and dry the wood on their violins. This would also hold true for anyone using the SG-1-40 for just about any purpose. This includes guitar makers, pool cue makers, etc.

So doubling the power output for your F64 (what we call our newest fixture) system will take you maybe 5 or 10 minutes is all. If you run your lights way up high, or you are using the bulbs in a greenhouse grow, then connecting that second wire is likely a wise investment as it reduces the number of fixtures you need to buy. If you are small grower using a 4x4 or 4x8 tent, you will NEVER need to worry about doubling the power, and in fact, we would strongly discourage it.


Example of running in each mode. The upper fixture is running at 40w, the lower at 20w. To the naked eye, it may not seem "twice" as much UV, but you can't see UV, so trust us, it is.


Dennis Brown

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