Fluorescent Shop Lights - Erratic Behavior

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  #1  
Old 03-17-05, 07:14 AM
kevcof
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Fluorescent Shop Lights - Erratic Behavior

Hi all,

About a year ago I installed four (4) duplex receptacles on the ceiling in the unfinished side of my basement (heated year round). I ran BX to a new 15A circuit in the panel, and wired the four receptacles to light via one switch near the doorway. I then hung four fluorescent shop fixtures (basic cheapo-disgusto Commercial Electric $15 light fixtures from Home Depot) from chains and plugged them into the receptacles. I loaded them with Philips T8-32 bulbs. All was well for about 9 months.

In the past few months, when I go to the basement room and flip the light switch, some of the bulbs will come on, and some will not -- maybe 4 or 5 out of the 8 total bulbs will fail to light. Some seem to flicker slightly, as if trying to come on. If I bang the sheet metal housing of the fluorescent fixture, the lights sometimes come on.

At one point, maybe 2 months ago, I went and replaced one of the fixtures at HD, and that one lit reliably for about a month, only to start acting like all the others again.

This morning, when I flicked on the switch, NONE of the bulbs lit. Prompting me to come here and yell HELP!

Questions:
1. WIRING:
a. Is it possible that I somehow screwed up the wiring and have faulty grounding (which , I have read elewhere here, is crucial to the fluorescent fixtures)?
b. I have tested voltage and ground using a voltmeter, and all appears ok, but maybe the "beep" of the VM when I test ground is not indication of a GOOD ground. Any better test for this?

2.) FIXTURES: Are the cheapo-disgusto Home Depot fixtures possibly the cause?

3.) BULBS: I hear Philips bulbs are not the best (but all HD carries). I've replaced bulbs from the case I bought, and that seems to help for a short while before misbehavior begins again.

Sorry for the long message -- wanted to make sure I gave all the info I thought relevant. Any advice is much appreciated.


kevcof
 
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  #2  
Old 03-17-05, 08:57 AM
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In all problems with fluorescent fixtures, the first thing to try is to replace all the tubes with new ones. Not some of the tubes--all of them.

Unreliable starting can also be caused by poor grounding or cold conditions. Finally, consider a new fixture or a new ballast. Considering a shop light these days sells for about $8, it not worth thinking about too long.

(1) Yes, it's always possible to screw up the grounding. How did you do it? Voltage to ground is not a good measure of ground quality. You have to load the connection. Some people rig up a 100-watt light bulb as a tester and touch the probes to hot and ground, and then to hot and neutral, and make sure the bulb is equally bright in both tests. If the problem is grounding, the lamps usually come on when you touch the metal reflector with your hand.

(2) Sure, cheap fixtures are always suspect. But I have $8 shop lights that have been performing perfectly for more than a decade.

(3) I have no problem with any particular bulb, but you might be into a bad batch. Try GE.

If none of the bulb light, maybe you don't have any power. You could even have an open neutral.
 
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Old 03-17-05, 09:24 AM
kevcof
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Thanks, John, for your thorough reply. I'll look at all of this on Saturday, and let you know next week how things go. I'm beginning to think the bad ground and/or open neutral theory may be at work here.

Thanks again,
kevcof
 
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Old 03-17-05, 11:27 AM
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Are you using the correct bulbs in the fixtures? Fluorescent bulbs must match the ballast.
 
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Old 03-17-05, 02:27 PM
kevcof
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Originally Posted by pcboss
Are you using the correct bulbs in the fixtures? Fluorescent bulbs must match the ballast.
I'll check, pcboss, but I'm pretty sure the fixture calls for T8-32w bulbs, and thgose are what I'm using. I'll check for sure tonight. Thanks.
 
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Old 03-17-05, 06:28 PM
kevcof
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Hi All,

UPDATE:

Based on the earlier replies, I figured I'd try and get some more data on how the gounding looked in my circuit. When I got home tonight, I checked the actual voltages in the four receptacles. I popped out the four receptacles and powered back on the circuit and took readings right at the screws. I'm glad I did because I think I have averted a disaster !!!!

I got the following readings:

Receptacle #1:
Hot-to-Neutral: 118v
Hot-to-Ground: 118v
Neutral-to-Ground: < 1v

Receptacle #2:
Hot-to-Neutral: 118v
Hot-to-Ground: 20v
Neutral-to-Ground: 90v

Receptacle #3:
Hot-to-Neutral: 118v
Hot-to-Ground: 30v
Neutral-to-Ground: 90v

Receptacle #4:
Hot-to-Neutral: 117v
Hot-to-Ground: 34v
Neutral-to-Ground: 85v

From what I understand, proper readings are 120v for H-to-G, and H-to-N; and zero (or close to zero) volts for N-to-G.

I immediately shut off the circuit breaker (the lights and switch are on their own circuit) since it looks like I have a serious problem, and probably could have burned my house down. Based on what I have read elsewhere in the forums here, it looks like I have what is called "feedback" between neutral and ground, and I think it is caused by a bad ground connection? It also appears to be a significant safety issue.

The circuit is wired S-R1-R2-R3-R4 (S=switch; R1=receptacle1, etc). It looks like the issue happens between R1 and R2.

* Should I just take out that wire between those two receptacles and rewire?
* Can there be any permanent damage that means I need to replace more components besides just the wire?
* Am I correct in assuming that there is a bad ground connection betwen R1 and R2, or is the feedback a symptom of some other problem?
* How did this all work fine for 9 months and then suddenly start having a problem only 3 months ago?
* Most importantly, whereas I am a DIYer, should I get a licensed elctrician in at this point? I'm not really not up for burning down my house and family. I'm worried about safety more than the cost at this point.

I'm pretty freaked out right now....

Thanks in advance for any guidance or reassurance (or scolding, if that applies).
 
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Old 03-17-05, 07:05 PM
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All of those in-between readings (34, 85, 30, 90, 20) are "phantom voltage" (google that term if you want). You have a bad ground. Check all the boxes on the circuit (yes, all of them) and see if it came loose somewhere.
 
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Old 03-17-05, 08:21 PM
kevcof
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Thanks, John. I'll do that ASAP and report back.

Just for my own peace of mind -- is/was this a serious safety issue if left as-is?

Thanks,
kevcof
 
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Old 03-18-05, 07:30 AM
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It's as safe as any ungrounded outlet, which means it's not an emergency, but should be corrected. Think of it as driving without a seat belt.
 
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Old 03-21-05, 10:56 AM
kevcof
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Thumbs up Thanks !!!

Originally Posted by John Nelson
All of those in-between readings (34, 85, 30, 90, 20) are "phantom voltage" (google that term if you want). You have a bad ground. Check all the boxes on the circuit (yes, all of them) and see if it came loose somewhere.
Hi John,

Well, you hit the nail right on the head. I went through the whole circuit on Saturday and did indeed find (inside the R2 receptacle) an open ground. The ground wire which fed out to the rest of the circuit from R2 had become somewhat untwisted from the other ground wire. It was making contact, but only tenuously....I made sure to retwist the two grounds nice and snug, and when I retested all of the receptacles, I got 117v on every single H-to-N and H-to-G measurement, and the N-to-G readings were all well below 1v.

When I plugged in my shoplights, they all fired up nice and bright (save one bulb that apparently was truly burned out, and which I replaced). Everything is now perfect.

I cannot say enough great things about this site, and I have been telling everyone here at work about how doityourself.com is the place to go for answers. Many many thanks for your help on this.

Best rgds,
kevcof
 
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Old 03-21-05, 03:55 PM
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Way back when, it was common to connect grounding wires merely by twisting them together. For reasons that are all to clear to you now, it is no longer allowed. You must use a wire nut on them.
 
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Old 03-29-05, 10:41 AM
kevcof
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Originally Posted by John Nelson
Way back when, it was common to connect grounding wires merely by twisting them together. For reasons that are all to clear to you now, it is no longer allowed. You must use a wire nut on them.

Went back in this weekend and put wire nuts on all the ground connections. Thanks!
 
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