VERY noisy Dimmers & Microwave Buzzes!?!

[CUS]

Hi
Oookay..#deep breath#...
I've just bought a house (built 1972ish) & had Spotlights all round. Most are on dimmers, and make a LOUD buzzing (can hear it right across room)... even hear them stood in another room with joining door open!

Lounge has a 2 gang dimmer..one for spots in the room, other for stairs/landing light (Normal bayonet bulby thing). Turn on lounge lights, very loud buzzing (from dimmer, not bulbs), but switching on dimmer to stairs (lounge dimmer off) makes no noise at all!
..Ive had electrican blokey change dimmers as I thought they musta been non compatable with halogens with the racket they made...they are MILDLY quiter, but still noisy!, but now the lights at certain levels when turning the dimmer up/down causes the lights to pulsate!?

#deep breath again#
Strangest thing was I bought an Expensive Microwave, got home plugged it in...and it was buzzing from the back (Very annoying) - very nearly jumped in car to throw it back at them! - anyhoo was Starvin, so had to use it!....went back in kitchin, no buzzing at all!? Lateron...buzzing again...- Turns out turning the lounge dimmer on causes the Microwave in the "kitchen" to buzz!?! Turned lounge dimmer off, microwave is silent! - all spotlights are on electronic transformers. in some rooms are low voltage, others high, but they all buzz in the same way

Oh...and!...We all keep gettin little static shocks off the dimmers (satin chrome)...electrician dude says that down to me putting laminate flooring down...builds static walking around?! - I woulda though the switch would be earthed/grounded, whatever the lingo is , so if u "was" statickated you wouldnt get a shock?

..Electrician dude says "Oh, all dimmers buzz to some degree" - Not sounding like a powerstation like mine do Chum! - if you stuck yer ear to it, and could hear buzzing, I wouldnt have a problem...I aint that Petty!, but my old house with halogens/dimmers (Ok...Mums house lol) you have to put your ear AGAINST the switch to hear the buzz...I even went back to check I didnt just "imagine" they didnt BUZZ like a pylon as mine do!

I have read, that "Cheaper" dimmers dont have a Filter/choke in them which is designed to cancel out the buzzing? - Electrican Assures me that they are NOT! cheap dimmers hehehe

Aaaaany Advise would be GREATLY appriciated!!
(..get a new electrican, I know LOL)

Pleeaase Help!!

 

[theshogun]

Take off dimmer ,make safe wiring , get in car go to mums ,trade dimmers ,see if problem still exists ie dimmer buzz on her lights if same.
If it does replace dimmer sw,have long chat with sparks .

If not check all switch connections are tight,earths are connecteds to switches as well as back boxes ,on the metal switches.

 

[CUS]

Thinking Batman!

I'm wondering if he's a Electrician or a Mortician?!

...One way to drum up business I suppose

Cheers! Deffo worth a shot. Now.......Where's me Screwy?.......

.......If your lights go out, you know I found one

 

[felix]

I suspect that those halogen lights have a 'transformer' hidden up there and it's not dimmable. (Too many things sold as transformers these days are nothing of the sort. They're switch mode PSU's.)

The buzz from the back of your microwave is most likely the transformer core sounding off. This one really is a transformer and they're all inclined to do that. It depends on how well the laminations are clamped/glued. So why does it go on and off with the dimmer?

Most probable answer: That dimmer is drawing current from your mains supply in spikes instead of smooth sine waves. These spikes contain lots of high order harmonics (multiples of the mains frequency). Your transformer core is a borderline buzzer and these harmonics just push it over the edge.

An earthed switch plate ensures that so DO get a shock if you're charged up but it's just as likely to be unsafe wiring. In fact the earth wiring of the entire lighting circuit (or house) might be faulty. This is a BAD THING!!! If a neon screwdriver glows dimly on that switch your earth is faulty. If the hairs on the back of your hand tingle when in close proximity your earth is faulty. If you go to switch the light on one day and bounce off the opposite wall --- your earth is faulty. Don't find out the hard way.

PS: In case you're tempted to open up your microwave looking for the source of the buzzing, BEWARE! The magnetron in my modest 600 watt microwave runs on eight THOUSAND volts! It also takes time to drain away after you switch off - and if the bleed resistor has failed it will take a very long time indeed. You need special equipment to work with this stuff. One false move and you'll have to be SCRAPED off the opposite wall!

 

[mapj1]

Felixs suggestion is the first thing to try - are the lights Low voltage types (read the rating from the bulbs..) and are the 'transformers' really that.
L-C Filtering may help, but is kind of tedious..
There is another more sinister possibility worth checking..
You may have a significant DC component to your mains - if you have a multi-meter, that does AC and DC seperately, check the AC component of the mains (you expect 230-240V) and then the DC, if this latter is more than 1V, you will start to have saturation problems with magnetic cores, as a static magnetisition causes the current waveforms to be off-centre.
It is usually caused by a large load with a single rectifier diode inside. That could just be your lighting dimmers, but it sounds rather unlikely, unless the supply impedance is not low enough - do the lights dim when you plug a kettle in for example?
Otherwise are you or a neighbour running a DC welding unit?
regards M.

 

[felix]

Good point from mapj1. I never even considered DC.

It is usually caused by a large load with a single rectifier diode inside. That could just be your lighting dimmers, but it sounds rather unlikely

How about a TRIAC firing in one direction only? As you point out though, the supply impedance would have to be rather high to create a significant DC offset with a lighting load. Surely there would be other symptoms - like the lights going out when the microwave starts up!

I think I'll abandon that theory and stick to odd harmonic distortion.

 

[delmel]

Try to match the loading as best as poss both on the transformers and the dimmer. There are dimmers made specific for low voltage but if he has used a decent electronic one then should have no problem. Note if transformers are Torodal type will need to have the inductive dimmers fitted