Top Document: Electrical Wiring FAQ (Part 2 of 2) Previous Document: Can I install a replacement light fixture? Next Document: What is 3 phase power? Should I use it? Can I get it in my house? See reader questions & answers on this topic! - Help others by sharing your knowledge Many fluorescent fixtures tend to buzz, objectionably so when used in residential (rather than warehouse or industrial) situations. This tends to be the result of magnetic/physical resonances at the (low) frequencies that standard fixture ballasts operate. You can eliminate this problem by switching to electronic ballasts, which operate at a higher (inaudible) frequency. Unfortunately, these are quite expensive. ----------------------------- Subject: Noisy lights with dimmer switches, what do I do? Often, after installing a dimmer switch, or replacing bulbs controlled by a dimmer, you'll start hearing objectionable buzzing or humming from the bulb. Sometimes it even interferes with televisions or radios. A little theory first. The voltage on the wiring in your house looks like this - a sine wave (forgive the lousy ASCII graphics ;-): ... ... ~ +160V . . . . . . . . ------------------------------------ 0V . . . . . . . . ... ... ~ -160V Most dimmers work by having a solid-state switch called a triac in series with the light bulb. Whenever the voltage passes through zero (it does this 120 times per second), the triac turns itself off. The control circuitry in the dimmer provides an adjustable delay before the triac turns back on. So, the resulting wave form looks like this: ... ... ~ +160V | . | . | . | . ------------------------------------ 0V | . | . | . | . ... ... ~ -160V As you can see, by varying the turn-on point, the amount of power getting to the bulb is adjustable, and hence the light output can be controlled. Voila, a dimmer! This is where it gets interesting. Note the sharp corners. According to the Nyquist theorem, those corners effectively consist of 60Hz plus varying amounts of other frequencies that are multiples of 60Hz. In some cases up to 1Mhz and more. The wiring in your house acts as an antenna and essentially broadcasts it into the air. Hence TVs and radios can be effected. This is called EMI (Electromagnetic Interference). As far as the bulbs are concerned, a bulb consists of a series of supports and, essentially, fine coils of wire. When you run current through a coil, it becomes a magnet right? If there's any other metal nearby, it'll move. Just like a solenoid. Further, when the amount of current flow abruptly changes the magnetism change can be much stronger than it is on a simple sine wave. Hence, the filaments of the bulb will tend to vibrate more with a dimmer chopping up the wave form, and when the filaments vibrate against their support posts, you will get a buzz. Worse, some dimmers only do half-wave switching, such that the one half of the chopped wave form will be absent. Which means that the current flow during the present half will have to be much stronger to produce the same amount of light - more EMI and more tendency to buzz. Solving buzzing problems: If you have buzzing, it's always worth trying to replace the bulb with a different brand. Some cheap bulb brands have inadequate filament support, and simply changing to a different brand may help. Try "rough service" or "farm service" bulbs. They're usually much stronger and better supported. Chance are, however, that switching bulbs won't make that much of a difference. Perhaps the buzzing will go away at some dimmer settings, but not at all. Buzzing bulbs are usually a sign of a "cheap" dimmer. Dimmers are supposed to have filters in them. The filter's job is to "round off" the sharp corners in the chopped waveform, thereby reducing EMI, and the abrupt current jumps that can cause buzzing. In cheap dimmers, they've economized on the manufacturing costs by cost-reducing the filtering, making it less effective. Perhaps the dimmer will be okay at some settings, but not others. Or be very picky about what bulbs to use. It is our belief that most buzzing problems can be traced down to cheap (<$15 dimmers), and most effectively solved by going to mid-range ($25-$35) dimmers from respected companies, such as Leviton. One of the authors of this FAQ, after learning this lesson, will still use $.89 outlets, but insists on better dimmers. By all means, try a different bulb first. You may get lucky. If not, it's time to swap dimmers. If you have EMI problems, it's almost certain to be a cheap dimmer. ----------------------------- Subject: What does it mean when the lights brighten when a motor starts? This usually means that the neutral wire in the panel is loose. Depending on the load balance, one hot wire may end up being more than 110V, and the other less than 110V, with respect to ground. This is a very hazardous situation - it can destroy your electronic equipment, possibly start fires, and in some situations electrocute you (ie: some US jurisdictions require the stove frame connected to neutral). If this happens, contact your electrical authority immediately and have them come and check out the problem. If you say "loose neutral", they will come. Note: a brief (< 1 second) brightening is sometimes normal with lighting and motors on the same 220V with neutral circuit. A loose main panel neutral will usually show increased brightness far longer than one second. In case of doubt, get help. User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: Electrical Wiring FAQ (Part 2 of 2) Previous Document: Can I install a replacement light fixture? Next Document: What is 3 phase power? Should I use it? Can I get it in my house? Part1 - Part2 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: clewis@ferret.ocunix.on.ca (Chris Lewis)
Last Update March 27 2014 @ 02:11 PM
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I bought a new receptacle and installed the same. I still have no power I suspect there could be a bigger problem,this is aluminum wiring.
I've killed the breaker and call an electrician but am curious as to what happened.P.s. there is a dimmer switch on the same circuit.
I have multiple switches to lights. Ran 12/2 and 14/3 into switch box and inspector wrote correction needed.
What should I have done instead?
thank you
dennis
Ex: 15 amp-14awg. 12awg-20amp only rule for thumb other factors such as continuous load,heating and others if you do not know the safe NEC rules then please call a qualified journeyman Electrician better be safe