Voltage drop on lighting circuit

[GAJ]

Trying to replace a ceiling pendant which has three-way switching. Voltage at the pendant is 230v.  But as soon as I put a load on it like a light bulb the voltage drops to 24v.  Light bulb is 5w LED.  I've checked the connections in the ceiling rose and light switches and all good.  Any thoughts?

 

[Fleeting]

What are you using to measure the voltage and are you measuring line to neutral or line to earth.

 

[Bruspark]

Sounds like you are measuring an induced voltage although it is unusual that it would be as high as the full 230.
What meter are you using ?

First question :  Did it work before you started ?

Second:  Did you photograph the old connections?

Third: What are you using to join the cables ?

 

[Sharpend]

Open neutral? 

 

[SPECIAL LOCATION]

Trying to replace a ceiling pendant which has three-way switching. Voltage at the pendant is 230v.  But as soon as I put a load on it like a light bulb the voltage drops to 24v.  Light bulb is 5w LED.  I've checked the connections in the ceiling rose and light switches and all good.  Any thoughts?

Without additional information such as requested by Fleeting..

i.e (What are you using to measure the voltage and are you measuring line to neutral or line to earth.)

Its all a bit of guess work...  :C

But you can always go back to basics...

(1) Assume EVERYTHING is faulty and/or connected wrong, until you have proved otherwise.

(2) Remove power from the circuit..  (use an approved voltage tested to confirm circuit is dead).

(3) Get an approved calibrated meter that can measure continuity.  

(4) Perform 'dead-tests' to verify polarity and continuity of all conductors at the light fitting.. 

(Including through all paths of the the 3-way switching you mentioned.)

(5) If any aspects of continuity are not confirmed as intact, trace and rectify broken continuity.

(6) Re-energise circuit, verify voltages are all present and correct with reference to a known proven earth reference point,  and all permanent lives, switched lives, and neutrals to confirm they are all correct.

(7) Insert a known good proven to work lamp into fitting...   all should be good!

Just a bit of basic fault finding..

NOTE:-

Neon screwdrivers, and basic <£30 digital multi-meters will probably give potential erroneous indications when used in inappropriate situations.      

Guinness

 

[GAJ]

Thanks all.  I inherited the job !  It wasn't working before I started.  The customer said a previous electrician had replaced two ceiling lamp fittings and then one stopped working.  Then the customer removed a fitting so quite honestly I don't know what the original connections were and they may well have been swopped around.  I have traced the various cores back to the switches using a long lead/continuity meter (power off obviously). The tester I am using is a Fluke voltage/continuity tester.  But I can use my Megger MFT 1553 to get accurate readings.

I think it is now connected properly but still can't phathom the voltage drop.  

 

[Fleeting]

I suspect you had a high resistance neutral connection which was only evident when load was applied to it. 

 

[Sharpend]

This is a classic case of open neutral. Obviously the alleged original spark had no clue what they were touching in the first place and incorrectly reconnected the light. 

 

[Murdoch]

Thanks all.  I inherited the job !  It wasn't working before I started.  The customer said a previous electrician had replaced two ceiling lamp fittings and then one stopped working.  Then the customer removed a fitting so quite honestly I don't know what the original connections were and they may well have been swopped around.  I have traced the various cores back to the switches using a long lead/continuity meter (power off obviously). The tester I am using is a Fluke voltage/continuity tester.  But I can use my Megger MFT 1553 to get accurate readings.

I think it is now connected properly but still can't phathom the voltage drop.  

Best next step is a R1 + R2 and a Rn + R2 - then compare the readings ..........

 

[GAJ]

Thanks.  I'm due back next week so I'll try that.

 

[binky]

you have to ask yourself why the fittings were replaced originally? Think you need to bell out the cct as in disconnect at the board and check continuity of the cct upto where you are working. 

 

[SPECIAL LOCATION]

Have you checked for any mess-up's between switched live and perm lives...

Reds / Blacks arse about face....

Polarity actually wrong at parts of the circuit.. 

Common after DIY light replacement... 

Seen DIY alterations where further lights down the circuit are actually fed from the 'N' side of an earlier lamp..

e.g.  So one or more lights are wired in series...?

May need to double check whole circuit, not just the "strange" fittings..

:C