Well if you are talking "electrical circuits" you want to wire them in PARALLEL not series. That is all the blacks together, all the whites together, and the grounds together.

If you mean, can you run the wire from the switch to the first light and then to the second, that's also allowed as long as you make the connections in a legal fashion. Many fixtures will allow you to make the connection inside the fixture.

Thanks for the response.

I am curious as to why they have to be wired in parallel?

Is it because of the ballasts?

There always seems to be some confusion about what in series vs in parallel means in wiring.
In common language, "in series" is generally interchangeable with "in a row." So, many people might see a circuit in which power goes to light 1, then light 2, then light 3 and say they are wired "in series." That isn't what "in series" means in the electrical world. In series would mean that the power came in on the live wire in light 1 and then came out the neutral wire of light 1 and went to the live wire of light 2, and so on. The current would go through the whole series of fixtures before returning on the final neutral.

What you actual want in electrical terms is for them to run "in parallel" - but they are still in a row. So, a live/neutral/ground run to light 1. A live/nuetral/ground run from light 1 to light 2 and from light 2 to light 3. At each light, you join all off the lives together, all of the neutrals together, and all of the grounds together. That way, current it running through each fixture individually or "in parallel."

syd81-
Do-it-yourself wiring always make me nervous when the question is this basic. I'm not trying to be insulting, but I want you to stay safe. You might consider getting a wiring book or a knowledgeable friend to help on this.

Thanks to all for the responses!

Bill - a special thanks for clearing that up. That was indeed where I was confused.

kudzu9 - Oddly enough, I checked several wiring books and none referred to "parallel wiring" at all - most likely because for the do-it-yourself job, as kurto said, everything is in parallel.

My confusion here came from the fact that I wired two fluorescent utility fixtures in a row (in parallel) they hummed as soon as I turned them on. I was concerned that the humming had something to do with my wiring. In researching whether the fixtures required anything special I encountered some inconsistent advice - which I now know is due to people using "in series" and "in a row" interchangeably.

Anyhow, evidently, my wiring was fine but a bad ballast right out of the box is not an uncommon event.

Again, thanks for all the help!

I wired 2 four bulb T8 fluorescent fixtures in parallel: power hot to switch to black wire of both fixtures then white wires (from both fixtures) to power neutral/white. Although both fixtures come on, they trip the breaker. They do it in a "weird" way: when I turn the lights on the first time, they come on & stay on. Then if I turn them off & turn them on again, nothing happens (no light, not even for a second) & the breaker is tripped. It seems to me if they were going to trip the breaker, they would do it the first time. I have tried this repeatedly after resetting the breaker, with the same results???????????????? Sometimes the lights will light up a second time, but not usually. Could it be a defective breaker?

Have you tried it without the bulbs in one and/or both yet? Is the breaker a GFCI type? What type of ballast Electronic or Magnetic? Is there a replaceable starter? Other than T8, what type of fixture is it? T8 is old tech ( although not as old as T12) and could be a lot of things including bad ballasts since they could be old, but I suppose you are talking about a more standard fixture with two ballasts in each fixture.

Additional info:

The fixtures were just recently purchased (new) at Lowes.

There is a single electronic ballast in each fixture.

Although the breaker does not say it is a GFCI, it has a "test" button on it which leads me to believe it is. They are in my garage.

I have not tried them with bulbs in just one. What is the logic/reason for doing that?

Additional comment: I was just replacing two four-bulb T12 fixtures that had bad ballasts so the wiring was already in place. I found a whole new fixture was less expensive than new ballasts.

The fixtures are the kind that fit in a 2x4 opening in a suspended ceiling.

Thinking there might be a grounding problem because the ground wire was solid core, with a painted green bolt, I worked on the grounding contact to make it better.

Also removing the bulbs from one of the fixtures, seems to fix the problem - so is the other fixture "bad" - but why does it come on at all?

"Also removing the bulbs from one of the fixtures, seems to fix the problem - so is the other fixture "bad" - but why does it come on at all?"

What happens if you remove the bulbs from the other fixture and leave them in the fixture you took them out of? I believe you will get the same positive results. I will explain further down.

"I have not tried them with bulbs in just one. What is the logic/reason for doing that?"

To see if one or both fixtures are bad, or in this case, if running only one fixture would still trip the breaker.

"Thinking there might be a grounding problem because the ground wire was solid core, with a painted green bolt, I worked on the grounding contact to make it better."

I believe it could be a grounding problem, but not in the way you think..... Were the grounds bonded securely to the metal trough/frame of the old T12 fixture?

"Although the breaker does not say it is a GFCI, it has a "test" button on it which leads me to believe it is."

This could actually be the problem. With most 4' fluorescent tube fixtures (unlike compact fluorescents) they are designed so that the "static electricity" leaks off to the frame. The grounded metal frame also helps the bulb start by helping the arc jump from one end to the other initially. The two fixtures together may be leaking more current to ground than the GFCI will allow, which makes it trip. Warm fixtures can start faster meaning higher voltage and more leakage (abbreviated explanation).

On the flip side, IF a better ground connection does help, then it may help the lamps start more smoothly, avoiding a spike in leakage current that would trip the GFCI.

Follow-up on previous notes:

The whole situation is baffling, doesn't seem to make sense & is very frustrating.

When I took the bulbs out of light A, light B worked fine (alone) & didn't trip the breaker. When I put the bulbs back in A (after having improved the grounding), it would not work at all & B was still working. I therefore figured I had a bad ballast in A & so returned it to Lowes and then replaced it. SAME STORY as original!!!!!!!!!!!!!!!!!

I made the following observations:

If the lights come on they stay on for that one particular "turn-on". They don't trip the breaker at that point, but do it when you turn it on a second (or occasionally third or forth) time. When turning on the lights does tip the breaker, it is immediate - ie the lights don't even come on for a second. A nightlight on the same circuit goes off the instant I flip the switch.

Since I got the new fixture, I at times get a few more "turn-ons" before they tip the breaker, but they still do. If I get more "turn-ons", it is more likely to happen if I turn the lights on & off fast & it is more likely to trip the breaker if I turn the light on for awhile, turn it off & then on again. It's like the longer the lights are on, the more likely they are to build up "some kind of breaker tripping 'something-or-other' ". ?????

Also, they are on the same circuit as the garage door opener & I can open & close the door with or with out the lights on without a problem - so it doesn't seem to be a voltage/power problem.

I can only conclude it is a "ground-fault" issue, but I can't make sense of it. I'm wondering if it is a "bad breaker".

It is a more common problem than you think, which is why I avoid putting fluorescent fixtures on GFCI circuits at all costs. In "theory" you should be able to put a reasonable number of those type fixtures on a GFCI circuit IF everything is working perfectly. It may help for a while to change the breaker. You may eventually find two fixtures that don't leak enough to trip the breaker for a while. It may require a more expensive ballast. Ballasts tend to leak more as they get older, in general. The starter capacitor, if there is one in the ballast, or just the starting of the lamp in general tend to leak more when they are warmer. It is just the inherent nature of the beast.

Thanks for your help!! I had been wondering if it was just me & I was overlooking something obvious. Logically, it was very frustrating. Since I have a suspended ceiling from the garage to the breaker box I think I will look into separating the lights on a regular breaker and put the rest of the outlets on a GFCI. Thanks again!

Let me help (hopefully) with the logic one more time. Try disconnecting the ground wire on both fixtures, making sure the ground wire doesn't inadvertently touch any other metal, and see how well they work. You may actually have to insulate the entire fixture from the suspended ceiling grid (lay it across a couple of plywood strips). You should find that one or both fixtures isn't working as well. That shows that a small amount of current was leaking to ground when it was working well. This in turn trips the GFCI.

Is the idea to isolate the fixture from ANY grounding - either from the ground wire or through the metal in the suspended ceiling strips?

Is the problem with the ballast giving off static electricity or a slow/minimal "short"? In either case, why wouldn't either cause the breaker to trip while the light is on rather than the next time the switch is turned on?

If the fixtures work better with the ground wires disconnected, do I leave them disconnected? Is that safe? Do I still need to isolate the fixture from the suspended ceiling strips?

Would it work to ground the fixture (the metal frame) to the suspended ceiling strips & ground the strips to something else (other than the grounding wire supplied with the power wire - & going through the GFCI) like pipe or grounding rod & leave the grounding wire supplied with the power wires disconnected from the fixture?

I will be out of town for about a week, so will have to wait to try whatever you suggest.

Thanks again for your suggestions on this bewildering puzzle!

1) yes, but that is just for experimental purposes so that you can see that there is a leakage to ground somewhere.

2) the bulb gives off a small amount of electricity when normally on, but not enough to trip a good GFCI. This is a little like static electricity, as you can often feel it in your arm hairs. This and the metal trough the bulb is in are part of the design so that the light runs smoothly. The starter is designed to create heat, which helps the bulb start. After the light has been on for a while, the heat weakens the insulation, which in turn creates a minimal short the next time you turn it on while the ballast is still hot. The two ways together create enough current leakage to ground to cause the GFCI to trip, especially with multiple fixtures.

3) they won't work better. The lamps need the "static electricity" part to run more smoothly with that long of a tube. I think the difference was more obvious in the old T12s. Not grounding the fixture properly for permanent use is not a good idea.

4) NO. ANY leakage current to ANY ground will still trip the GFCI. If what goes out of the GFCI on the hot wire does not come back into the GFCI through the neutral wire, the GFCI will trip with very little room for error. The ground wire doesn't actually go through the inner workings of the GFCI, and where the current gets lost to has no bearing on whether the GFCI will trip.

One last note before going out of town - I'm still trying to understand what is going on in this situation:

I understand that the GFCI looks for a current difference between the hot & neutral wires. I mistakenly thought current in the ground wire also tripped the GFIC breaker. What I don't understand is if the GFCI is sensitive to a "leak", why doesn't it trip during the first time the light is turned on. It seems as though if current is "leaking" it should go off when or while the light is first turned on. It's only after the first time that it trips & only after turning on the light again (not before - I have checked the breaker to see if it trips when turning the light off after the first "turn-on" & it doesn't). To my way of thinking (?), it's as though the first "turn on" leaves some kind of current behind (? in a capacitor or something?), and then when I turn the light on again, that current is "released" & trips the breaker. -???????? If that is the case, is there anyway to "bleed off" that current? (That is where my idea in the last note came from)

First, "(not before - I have checked the breaker to see if it trips when turning the light off after the first "turn-on" & it doesn't)."

It better not. The circuit has been interrupted, although there is a way to trip a GFCI without a current in the hot leg, it would do it whether the switch was on or not.

"To my way of thinking (?), it's as though the first "turn on" leaves some kind of current behind (? in a capacitor or something?),"

Not quite the way a capacitor works in general, it should not let extra current through just because you turn the light on. That would probably mean a blown capacitor, and nothing would work. Some of this stuff can hold a small charge, but that isn't the problem.

Many fluorescents start with both a capacitor AND a higher voltage at startup to get the arc to initially jump the 4' gap. It is usually the insulation failure of the capacitor/starter due to the heat that was generated during the last use combined with the higher starting voltage that causes the problem. The insulation value doesn't degrade enough to leak at normal operating voltage. The type of insulation we are talking about can melt when it gets hot, and then resolidify when it cools (intentionally), making the insulation work just fine at the startup voltage once cooled. A plastic insulation (such as what is on THHN), in this case, would not hold up to the heat, and does not repair itself. Have you ever seen a black substance leak out of a ballast that looks and smell something similar to tar?

A GFCI indeed measures current balance between the hot and (grounded) conductors, but there's another thing going on. It puts a small signal on the two wires together such that a neutral-to-ground fault will trip the breaker.

This isn't a smart switch or the like (or perhaps even an illuminated one) is it? It's possible to miswire them (especially to put a neutral connection to ground) that will annoy a GFCI.

I have a question. I have 2 sets of 480-xlh-tc-p ballast garage lights I installed in my garage. The house came with 2 regular bulbs. First bulb had a ground, 2nd one did not. I disconnect the first bulb and hooked up my florescent lights, boom it worked. Turned power off and hooked up the 2nd set of florescent lights and grounded it. Turned power on, 2nd set of lights work and the first set doesn't power up all the way.

Turned power off, disconnected the 2nd set, turn power on and still the forst set doesnt power on. Connected the 2nd set without ground it comes on but first set doesnt??

In my old house I installed these lights the same way. What gives?

Want to add, the forst set has power still, just barley lights up on the ends of the bulbs...

Hi

Hope someone can throw some light Pardon the pun.my outside light is cactus so im replacing it with a fluro my problem id i have an extra separate white wire that i dont know were it comes from

Have the normal green/yellow =earth the black =N and red = L which is connected but light dont work i just don'tknow were this completelyseparate white wire goes

Any help would be greatly appreciated

Stephen-

1. Suggest you start a new post since this is off-topic from original post.

2. Re-read and edit what you have written: the typos and lack of punctuation make it unclear.

3. Include a picture or two with your post, to be on the safe side.

You do not run "white wires together". Your neutral (more properly known as the "grounded conductor") from each light ballast goes to the neutral bus bar in your panel. If you connect all of your neutrals anywhere else, current will not have a direct path of flow and will go wherever the path of least resistance to ground is. If that path is not the panel you are supplying from, you will have issues with breaker tripping.