Tandem Wiring

[bphgravity]

Can anyone tell me what this means and why it would be in the energy efficiency codce?

Luminaires designed for use with one or three linear fluorescent lamps >30W each shall use two-lamp tandem-wired ballasts in place of single lamp ballasts when two or more luminaires are in the same space and on the same control device.

And what does the term "EFFICACY" mean? An example, "Exit sign luminaires operating at greater than 20 watts shall have a minimum source efficacy of 35 lm/W."

 

[peteo]

Re: Tandem Wiring

Both terms are used in meeting Cal Title 24 energy standards, and will likely show up in ICC documents as well.
Tandem wiring is what the architectural schools came up with for dimming rows of fluoresents with non dimming ballasts. I first saw it used as a mandatory measure in the 2001 Cal code. There was a legal definition buried in the compliance manual, but it means that 1) Long rows of fluorescents have alternating sets of lamps turned off, i.e., every other ballast along the row now has a separate control or switch, used for daytime dimming 2) You could skip this if your fluorescent run was 3 or less fixtures long. Grr, they do not have the term either in the glossary on their web site or in the 2005 standards. From 2001 5.2.1(h):' Tandem Wiring (?132) Pairs of one-lamp or three-lamp recessed fluorescent' 2005 131.2.B '2. Switching alternate lamps in luminaires, alternate luminaires, and alternate rows of luminaires.' Yes they dumped the term, and rewrote the numbering system. I'm sorry I deleted my 2001 manual with the official legal definition.
Efficiacy is a textbook word for efficiency. Look at the units. How many watts for how much light. The new 2005 wording defines 'high efficiency' and uses that for some installations, where for others calls out the number directly (nonres outdoor must output 60 lumens/watt, which forces HPS or pulse start MH.) One other term they now use, is 'cutoff' fixtures at 175 W & up. Darksky.org has a page with excellent educational references.

 

[charlie b]

Re: Tandem Wiring

My dictionary defines "efficacy" as "the capacity for producing a desired result or effect." That is not the same as "efficiency." The later term has to do with getting the desired results at a low cost (i.e., lots of light for a small amount of watt-hours).

If you are looking for a certain value of foot-candles of light at the desk level, and if you want the light levels to be fairly constant throughout the office, and if you install a lighting system that achieves these two goals, then you can say the lighting system has a high efficacy. You can say that even if you used light fixtures that are old-styled, inefficient, expensive, and expensive to operate.

 

[sandsnow]

Re: Tandem Wiring

Charlie
Here in CA, we like to make up our own definitions , Thank You Very Much.

From the 2005 Building Energy Efficiency Standards:

Efficacy, Lamp is the quotient of rated initial lamp lumens divided by the rated lamp power (watts), without including auxillaries such as ballasts, measured at 25'C according to IESNA and ANSI Standards.

Efficacy, Lighting System is the quotient of rated initial lamp lumens measured at 25'C according to IESNA and ANSI Standards times the ballast factor, divided by the input power (watts) to the ballast or other auxillary device (e.g. transformer); expressed in lumens per watt.

Bryan's "tamdem" luminaires are nothing more than a master slave setup to eliminate single lamp ballast. Read all about our energy reg's here CA T-24 Energy

peteo
I must remember the reg's incorrectly, because
I'm 99% sure that Tandem = Master/Slave. Required when luminaires were w/in 6' of one another.
Anyway, 2001 regs are in the trash. I'll have to research this in the 2005 reg's and see what's equivalent.

 

[peteo]

Re: Tandem Wiring

Charlie,
After reading your post I looked it up. My old copy of 'Mechanical and Electrical Equipment For Buildings' (6ed, Wiley, 1980) says: "The efficiency of a light source is termed its efficacy, and is measured in lumens per watt."
Luminous Efficacy is available as one of the secondary possibilities when one Googles the word efficacy. It apparently has a separate meaning when dealing with lighting. And I couldn't agree more that it obfusticates the root word's meaning and intent.

 

[bphgravity]

Re: Tandem Wiring

Well, it apears Florida is mirroring CA Energy Code. This and many other sections are now apart of our building code, Chapter 13-4.

 

[don_resqcapt19]

Re: Tandem Wiring

Tandem wiring is where the two lamp ballast and one lamp is in one fixture and the second lamp is a second fixture. This elimates the extra energy that would be wasted if single lamp ballasts were used.
Don

 

[bphgravity]

Re: Tandem Wiring

Thank you Dorene!

I saw your posting to the International Association of Electrical Inspector's web site today regarding tandem wiring, and can answer most of your questions.

1. Tandem wiring - Tandem wiring is when 2 light fixtures share a ballast. For example, 3-lamp parabolic fixtures are often wired so that the center lamp can be switched separately from the outside 2 lamps. Some refer to this as stepped switching, others as bi-level switching. To step switch two 3-lamp fixtures you would need to use 3-two lamp ballasts. One fixture would have two ballasts. One 2-lamp ballast would control the outboard lamps, and the other 2-lamp ballast would control the center lamp of one fixture, and the center lamp of another. So, this ballast is "shared" between 2 fixtures. Then the other fixture would have one 2-lamp ballast controlling the outside 2 lamps.

2. Why is it in the code? Because it's more energy efficient to use a 2-lamp ballast, rather than many single lamp. For example, a 1-lamp electronic ballast for a 32-watt T8 lamp uses 32 watts. A 2-lamp ballast for the same lamp uses 58 watts. So, 6 watts are saved by using the 2-lamp ballast (32 X 2 = 64 - 58 = 6 watts) In addition, I believe they are trying to encourage step switching as described above.

3. Definition of efficacy - Efficacy - how efficient a lamp is to operate. This is measured in lumens per watt. Lumens is the light output of a lamp. For example, a 32-watt 4 foot T8 lamp puts out about 3200 lumens. Divide this by the lamp watts, and the lamp efficacy is 3200/32 = 100 lumens per watt, or lm/W.

I hope this helps you out.

Sincerely,

Dorene Maniccia