VHO Ballast question

[sleeman]

I have an Advance R-2s110-tp magnetic ballast. It will run up to 2-96" t12 110w HO bulbs. In my simple mind, this should power 2 48" 110w VHO bulbs as well. I don't have the ability to test my theory.
Anyone know if this will work?

Cheers,

Al

[StirCrazy]

Originally Posted by sleeman

I have an Advance R-2s110-tp magnetic ballast. It will run up to 2-96" t12 110w HO bulbs. In my simple mind, this should power 2 48" 110w VHO bulbs as well. I don't have the ability to test my theory.
Anyone know if this will work?

Cheers,

Al

it might start them it might not, it won't run them to VHO levels either way though as the current for HO is lower than that for VHO.

Steve

[Rikko]

Steve, can you explain that in a little more detail? I've heard that bit before but it never made sense to me. If the ballast can provide 110W, what difference does it make if it's a 110W, 12' long NO or a 110W, 4' long VHO? With Watt's Law (err.. I think it's Watt's Law) power is just the product of current and voltage, and I'm betting that the voltage between all of the fluorescent species is standard. Where does this disconnect in logic with the VHOs happen? I certainly don't doubt it, but I can't grasp where it's happening.

[Invigor]

don't quote me on this, but it's probably harder to fire a vho bulb (takes more voltage to start) and the ballast just doesn't have the drive to fire them up to 100%.

this is just a guess.

think of it as an indy car has ~800hp. if you put an indy car engine in a semi and try to pull a fully loaded 53' trailer, it ain't gonna happen. although it still is 800hp, it just doesn't have the torque to get the tires rollin'.

[StirCrazy]

Originally Posted by Rikko

Steve, can you explain that in a little more detail? I've heard that bit before but it never made sense to me. If the ballast can provide 110W, what difference does it make if it's a 110W, 12' long NO or a 110W, 4' long VHO? With Watt's Law (err.. I think it's Watt's Law) power is just the product of current and voltage, and I'm betting that the voltage between all of the fluorescent species is standard. Where does this disconnect in logic with the VHOs happen? I certainly don't doubt it, but I can't grasp where it's happening.

I will quote a paragraph from my write up in the newbie area, if you want to read it all the link is
http://www.canreef.com/phpBB2/viewtopic.php?t=7740

"the difference between NO, HO and VHO ballast, basically in a simple system it is the maximum current that the ballast is designed to output. This means that a ballast made for NO lighting will be able to put out a max current of 0.4Amps, a HO ballast outputs around 0.8Amps (also the same make up as a ballast for Power compacts), and a VHO is approximately 1.5Amps. All this doesn't tell you how much power the actual tube consumes though, as this is also a factor of the resistance of the tube. To make different wattages of tubes the manufactures build a specific resistance value into the tube its self, so that when this resistance is added to the resistance of the ballast you can then use the current to figure out the actual tube power output. Lucky for us this is labeled on the tubes and we don’t have to do the math. "

so basically the transformer is a constant current generator that will supply its current rating up to a maximum wattage. so a 80 watt NO ballast will supply 0.4amps constant current up to a maximum power rating of 80 watts. So a HO ballast only puts out a current of 0.8amps but to the rated wattage, but a VHO bulb is designed to run on a 1.5amp current.

some times a VHO bulb will run on a HO ballast if the starting method is right, but it will only run at HO levels. so if you have a 110 watt VHO (if my math is correct) it has a resistance of about 73 Ohms, so running this bulb on a HO ballast will give you a power output of 58 watts (which I think is the approximate rating for a 4 foot HO bulb.

Steve

[Rikko]

Interesting.. So where does the difference between NO/HO and VHO come in? On my WH7 I ran a NO and a HO T5 on different leads. The HO (39W) was definitely running HO (well, visually it was an enormous deal brighter - I didn't hook up any meters). Suppose I stepped it down to smaller bulbs so that a VHO bulb were 40W (say it's a theoretical 12" VHO tube). (I do this only so we have a single output lead for my Workhorse ballast for any bulb type). I connect my 12" NO = light. I connect my 12" HO = light. Now I connect my 12" VHO = how much light? Will it run at HO but not VHO? Is the electronic ballast able to dump out a variable amount of current for each bulb type, but just not enough for a VHO?
<even more confused than before>

[StirCrazy]

ok electronic ballasts are different, you can make them configurable by the amount of leads you use per bulb. so, if you use 1 red wire you are putting out the current level for an NO bulb or about 0.4 amps. If you hook two red wires to one side of the bulb then you are running HO configuration at 0.8 amps, If you use 3 red wires to one side of the bulb you are running VHO output at 1.5 amps. myself I use all 4 wires to two VHO bulbs in series so I am actually overdriving VHO bulbs, but I don't recommend wiring this way unless you know what you are doing as we have seen hooking it up wrong in a series overdriven VHO set up will melt end caps

so if you run any VHO and you want to run it to proper levels you have to use 3 out of the 4 wires for one bulb. Now you can use two wires and run it at HO levels, this is basically how IceCap works. you can either overdrive NO or under drive VHO using two wires per bulb.

Steve

[Rikko]

Yeah, I'm with you up to there (it ties into the ODNO fanatics that are throwing it onto their planted tanks), but it doesn't jive with my experimental results. My NO and HO T5s were both on the same ballast with a single lead each and the HO was spectacularly brighter. Is this possibly a trick with the T5 design? I know there's "something" different about them than just being a smaller T12 tube.
Or should I just hook up a meter and see? I assume ammeter in series between 'hot' lead and the bulb should tell me what I want to know?

[IslandReefer]

I would think a measurement would be very revealling.
My suspicions are that the smaller diameter T5 bulbs just "apppear" brighter .
Staying tuned

[StirCrazy]

I don't know much about the T5's but the smaller you get the more intense the light is so that could be a factor.

Steve