# T8 Lighting Ballasts, Design



## NolaTigaBait (Oct 19, 2008)

none that i know of...that ballast is made to operate 1 or 2 lamps


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## MikeySq (Jun 18, 2009)

on the schematic on the ballast it lists operation for 2 bulbs, there's no mention of single bulb operation.

If it is OK would the energy consumption be cut by 50%?

Mike


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## k2x (May 20, 2008)

Most 2 lamp instant start parallel wired e ballast are listed for one lamp. The power will increase slightly and the current draw will decrease. I think you should cap the lead and not wire it to a vacant lamp holder. 

A 2 lamp rapid start, series wired e ballast will not operate without 2 lamps.


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## MikeySq (Jun 18, 2009)

in a 2 bulb f32TX fixture is there significant energy savings(kW/h) by removing one bulb and letting the fixture operate with only one bulb?

would there be bad side effects to doing this?

thanks mike


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## Toronto Sparky (Apr 12, 2009)

I have never seen a problem even with the four lamp electronic ballasts.
I've been in a lot of offices where they complain the lights are too bright and just pull a couple of lamps.
Months later they change their minds and put them back in.. No problems

Even back in the Magnetic ballast days I used to use two lamp ballasts to power one lamp by ignoring (and capping off) the yellow wires. They worked for years.


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## k2x (May 20, 2008)

MikeySq said:


> in a 2 bulb f32TX fixture is there significant energy savings(kW/h) by removing one bulb and letting the fixture operate with only one bulb?
> 
> would there be bad side effects to doing this?
> 
> thanks mike


If the 2 lamp ballast is rated for 1 lamp , the label will list the amp draw with one lamp, or two lamps, and also some different type of lamps too. It should drop the voltamps by about 40%... 

A ballast should be used for it's listed use. 110.3 (b)... Although I've done a few sucessful experiments i don't think I'd do it it on sombody else's property.


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## Lighting Retro (Aug 1, 2009)

Toronto Sparky said:


> I have never seen a problem even with the four lamp electronic ballasts.
> I've been in a lot of offices where they complain the lights are too bright and just pull a couple of lamps.
> Months later they change their minds and put them back in.. No problems
> 
> Even back in the Magnetic ballast days I used to use two lamp ballasts to power one lamp by ignoring (and capping off) the yellow wires. They worked for years.


You should have no issues. We often stock 2 and 4 lamp ballasts, but occasionally must replace a 3 lamp ballast. What you have mentioned should not cause any problem at all. However, on the energy saving side, it is slightly less than 50%. You'll notice on all manufacturer charts that the more lamps per ballast the more efficient they get. Not by much, but some. You might lose a couple of % points for efficiency, but the only true way to test is to hook it to you watt meter for kicks.

http://eqas.mysylvania.com/content/display.scfx?id=003678734

Here's a link to a standard ballast type of sheet you will normally see. As you can see, there is no documentation on a ballast using less than the designed lamps. You probably won't find a chart on this specifically, so everything you get will be from in field experience and conjecture most likely. Hope that helps.


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## drsparky (Nov 13, 2008)

Why don't you put a clamp on ampmeter and try it with one lamp and two? Tell us what you find.


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## Lighting Retro (Aug 1, 2009)

drsparky said:


> Why don't you put a clamp on ampmeter and try it with one lamp and two? Tell us what you find.


actually have me a bit curious as well. Might even do it myself....


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## JvH87 (Jul 21, 2009)

Got me a bit curious too keep us posted :thumbsup:


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## Lighting Retro (Aug 1, 2009)

any updates?


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## Electric_Light (Apr 6, 2010)

It depends on each ballast. parallel instant start ones tend to be flexible. If it isn't published, you'll need to contact the manufacturer and ask about possible configurations. Wiring up for an unsupported configuration may result in a premature ballast and/or lamp failure.

Don't ask me why, but for T8 ballasts, normal output ballast means 88% output, which means that a lamp rated at 3000 lm will produce 2640 lm. "normal" CFL ballasts and magnetic ballasts are usually spec'd at 95-100% output. 

The label on ballast or the brief brochure don't tell you all the possible combos. 

A normal output Sylvania 4 lamp ballast will operate 4 32W lamps at 88% output, 3 lamps at 96% output. The 4 lamp ballast can ONLY operate THREE 40W (F40T8, 5ft) lamps. If you wire up four, it will light up, but I'm guessing it will burn out.


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