Light fitting connections

[Jontomwilliams]

Hi all, just moved into a new house have zero experience in replacing light fittings so any advise world be great thanks.

All pictures attached.

1. The first part is that I have bought this light fitting, as it was too long I cut the wire length it was copper on the top and as you can now see the wires are silver coloured are they still ok to be connected to the ceiling fitting.

2. Secondly from what I understand the wire labelled N would go next to the blue cable in the ceiling fitting. Then the wire labelled S would go next to the brown wire in the light fitting can you let me know it's that's all correct?

3.Lastly where would the earth wire from the light fitting go, we connected it to the earth wire in the ceiling fitting but when we turned the light on the switch made a buzzing noise.

I understand being this clueless I may need to get an electrician on so if that's the only advice no problem.

Thanks in advance

 

[telectrix]

what lamps (bulbs) are fitted, and is the switch a dimmer?

 

[PEG]

Hi fella,i'm not going to say the obvious,coz you may have already guessed it

The problem with remotely advising what colour of conductor,goes where,is knowing whether or not,they are correctly wired and coloured,to begin with.

Saying the green/yellow wire,definitely goes to the earth connection,is all well and good,if that conductor does not turn out to be live

Conductors can be marked up incorrectly,EVEN if the previous light fitting was working.

Like i said,i am resisting the stock answer,to this regular conundrum,but i will say,please get assistance from someone with electrical knowledge,to ensure the wiring identities are correct

 

[PEG]

Fair play to Tel,to throw in a couple of other vital puzzle-pieces,which are pertinent to the job,instead of a usual reply.

Although the gist is the same,manners makyth man

 

[littlespark]

What you have done so far has been right. It doesn't matter putting the silver strands of wire into the terminals, but try to get them all in.
N to neutral, the blue cable.
S must mean switchwire, the brown.
Earth, green and yellow, to the green and yellow.

The buzzing may be the lamp, or fitting itself. You haven't showed us the actual type of fitting it is.
As mentioned, dimmers can cause buzzing with the wrong type of lamp
And as mentioned, we are assuming the fixed wiring of the house to be right. (although you cant go much wrong with whats there)

 

[Jontomwilliams]

what lamps (bulbs) are fitted, and is the switch a dimmer?

Hi it's not a dimmer and this is the bulb thanks

 

[DPG]

I would say this should be straightforward if it wasn't for the buzzing that you mention. Are you sure the switch isn't a dimmer? Did you ever have buzzing from the switch before?

Is it definitely buzzing, and not an arcing sound?

 

[Jontomwilliams]

I would say this should be straightforward if it wasn't for the buzzing that you mention. Are you sure the switch isn't a dimmer? Did you ever have buzzing from the switch before?

Is it definitely buzzing, and not an arcing sound?

Hi yes this is the switch

 

[telectrix]

if the switch is buzzing, it's usually ether overloaded ( rare) or faulty.

see below:

 

[PEG]

Just as an interest,i had a buzzing switch,on a lounge light fitting,which traced back to a conductor,arcing to the slip-conduit,under the landing floorboards. If i remember correctly,it stopped,if you tapped it,but would resume buzzing,soon after

 

[Lucien Nunes]

A straightforward non-electronic light switch should not buzz regardless of the kind of lights connected. The buzzing is likely to be arcing that indicates a bad connection or bad contact that could overheat and cause danger. The switch and its wiring need to be checked. Most likely the fault was already there, but it has been revealed by installing the new light fitting that puts a greater or more capacitive load on it.

 

[marconi]

As a Thursday brain-stretcher I'd be interested to read explanations of why LN said in #11:

(1) a more capacitive (aka higher leading power factor) load would make the buzzing sound stronger (in an ac circuit).

And then to extend further,

(2) is it a more capacitive or more inductive load that would make the buzzing stronger in a dc circuit? Or neither?

 

[DPG]

A more inductive load would have no detrimental effect to the buzzing if it were a DC circuit, as an inductor only affects AC circuits. This is the reason smoothing chokes are used on DC power supplies.

Any points for that Marconi?

 

[Lucien Nunes]

OK, I didn't phrase that very well. What I meant was a load such as a switched mode power supply (e.g. LED driver) that rectifies the mains to charge a reservoir capacitor. The capacitor charges only on the peaks of the waveform when the instantaneous voltage exceeds the capacitor voltage, so the crest factor is higher than with a resistive load. If the series impedance is low, the peaks can be very short and very high compared to the RMS value, disrupting a faulty contact every half-cycle where a sinusoidal current of the same RMS value would not.

A load that is simply inductive or capacitive, taking a lagging or leading sinusoidal current, will not cause any different effects to those of a resistive load in a steady state, although the making and breaking behaviour can be different. It's worth noting here that some of the transient effects often attributed to 'inductance' such as transformer inrush, are actually due to magnetic saturation where the inductance decreases, not the inductive nature of the load itself.

One can actually tell quite a lot about a load by the sound and appearance of the arc it causes. I could probably tell the difference between a tungsten lamp, a TV and an induction motor of the same power rating just by watching switch contacts making and breaking its supply.

E2A:
Surely Marconi means the AC component of a non-constant current in a DC circuit, on which an inductor has the same effect as in an AC circuit (e.g. the smoothing choke referred to.) In this case it's immaterial, as my point was not really about reactance but rectification.

 

[marconi]

Re #13 and E2A - yes.

 

[marconi]

Duplicate post

 

[marconi]

As ever LN #14 provides a very nice elaboration. My apologies to him for not making the immediate link in my mind to non-linear loads such as SMPUs and smoothed rectified supplies.

What struck me about what he first wrote - revealed by installing the new light fitting that puts a greater or more (net) capacitive load on it - is that this is true but also a less net inductive load would also make the buzzing louder. Think net impedance Z and how that changes with the amount of LCR in the circuit and current through the arcing contacts is V/Z.

A time varying dc current can be considered to be a constant average current added to which is a time varying component. The constant part of the dc current would cause next to no arcing sound - it is constant therefore there is no time variation therefore no change in arc strength therefore no mechanical sound waves produced. The inductance and the capacitance in the circuit cannot help themselves from reacting to the time varying component and you know how they do that through their associated changing magnetic and electric fields/flux. The time varying component will cause the arc to vary in strength over time..........