A few questions about wiring fluorescent light fixtures in series:

• Can I mix new T8 fixtures (2 bulb, 48") with old T12s (5 bulb, 48") on the same circuit/switch?
  
• Can I determine if the old fixtures are working without buying a bunch of bulbs?
  
• Does wiring in a "series" cause any issues like with Christmas lights - i.e., if a bulb goes does it affect other fixtures down the line?
  
• How much bulb wattage can a 20 amp circuit handle? There are also a couple of outlets on the circuit where I might have to plug a tablesaw, so I'd want a lot of wiggle room. The T8s are 32 watt.
  
• It's a 20x30 garage/workshop (600 sf). I'm currently planning on the two T12 fixtures that I have and four of the T8s, plus I'll add some area lights over benches. Sound adequate?
  

 

Fixtures yes. bulbs no.

Just enough new bulbs to test each ballast in the fixture or swap bulbs from a known good fixture.

AC wiring is never wired in series. I think you are confusing "daisy chained in parallel" with series wiring. Daisy chained wiring is parallel and does not cause problems.

I would put on a dedicated circuit (no receptacles) if actual amps used by the fixture not bulb wattage approached 80%. Actual amperage is higher then bulb wattage because of the ballast.

If you use only T8s no need for multiple spare bulb types, less energy, and brighter. In most cases the T12 can be converted to T8 but in a 5 tube fixture might cost more then it is worth.

 

The T-12 fixtures figure apx. .63 amp per ballast, T-8 figure .24(2/3 amp and 1/4 amp thereabouts. To figure the lamps most likely you have F40 energy savers (32w) and the t-8's are 32w as well. take the total watts , divide by volts (120) to get amps. then add in the ballast usage. You should not go over 16 amps on the 20 amp circuit. Now if you have old 40 watters on the t-12's figure 40w each lamp. this is pretty close. I have a 20x24 garage. In it I have 4 x 2 tube 8ft strip lights, 1 x 4' work bench light, and a dusk to dawn light wired in as well as a 20 amp dedicated circuit and a 20 amp circuit that controls 3 other outlets and or outlet strips. I also have a 240v air pump circuit and I have a retractable outlet on the same circuit as the dusk to dawn light. If I remember right I have the 8' fixtures on a dedicated circuit, more for my desire to have circuits split up than anything else. Works pretty well for me as far as lighting goes. I have one - 30 amp 240volt circuit feeding it all.

 

Ray2047 wrote: "AC wiring is never wired in series. I think you are confusing "daisy chained in parallel" with series wiring. Daisy chained wiring is parallel and does not cause problems."

I never consider eHow.com the authority on anything, but they call it a series - is the method right even if the terminology is wrong (How to Wire Fluorescent Lights in Series | eHow.com)? Or would you have a diagram? Main idea is to get the multiple fixtures to go on with one switch. Nothing in the fixture instructions.

 

You have a series of lights each wired parallel. The article at best is poorly worded. Never wire AC devices in series.

 

Hi, just to follow up on the parallel diagram, do the lights need to connect directly to each other in sequence or can I branch off in an electrical box to, say, two lights, then run the line on to additional lights? If this doesn't make sense I can send a diagram.

 

You can branch off just watch you don't exceed box fill.

 

So this is good, right?

 

Circles are boxes with splices

 

Yup! you just need to keep the boxes accessible.

 

But you don't need extra J-boxes. The J-boxes the lights mount on can be used for that purpose.

 

They're fluorescents. I can do the splices in the fixtures, but I think sometimes I will save on cable by having a junction box (plus I can add more lights). Make sense?

 

Yes.

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