195v on a domestic lighting circuit

[ianbrookes]

any ideas would be gratefully accepted.

went to a job today. no upstairs lighting at all, did various tests, 240v at the CU, 195v at several of the fittings.

lighting is loop in ceiling roses/fittings, switches are line in and swl, mixture of dimmers and switches.

to bathroom fans on isolators, pullcords in bathrooms to operate lights (and assume switch fans - I couldn't test, not enough voltage)

circuit is small in length and number of fittings.

has anyone come across this before ?

 

[sparks55]

Isolate and do IR see what is pulling down voltage

 

[telectrix]

first of all, have you tested L-E at fittings? if that gives you 240V, then it's a neutral fault.

 

[Silly Sausage]

Dodgy Line connection upstream of the first light fitting, possibly...

 

[brman]

240V at the output of the fuse I assume? L-N? L-E? N-E?
195V across what? Loop at the rose? L-N? L-E? N-E?
L-E and L-N loop impedance at the fittings?

 

[brman]

Isolate and do IR see what is pulling down voltage

You would need a very low Ipf to take 50V off the voltage without blowing a fuse........

 

[Farmelectrics]

neutral fault to me

 

[ianbrookes]

242v at output of fuse in CU L-N
195V at fittings L-N
even the first fitting does not work
there is a two-way switch in the downstairs, no neutrals, just line conductors - this doesn't work for the landing light either

it must be a bad neutral somewhere, the cable is in really good shape, no signs of any degradation (what I can see anyway)

thanks to all

 

[HandySparks]

went to a job today. no upstairs lighting at all, did various tests, 240v at the CU, 195v at several of the fittings.

When you say "no upstairs lighting at all", do you mean that there was not enough current to light a lamp? If you are measuring this "195V" with no load on the circuit, then there's probably a break in the supply and the voltage you are measuring is a phantom or induced voltage.

What is the voltage with, say, an ordinary GLS lamp across the supply? If zero, or close, then it's a break rather than a resistive fault.

 

[Engineer54]

242v at output of fuse in CU L-N
195V at fittings L-N
even the first fitting does not work
there is a two-way switch in the downstairs, no neutrals, just line conductors - this doesn't work for the landing light either

it must be a bad neutral somewhere, the cable is in really good shape, no signs of any degradation (what I can see anyway)

thanks to all

Well, that will tell you where to start looking for the fault on this circuit then, won't it! ...lol!!

 

[SYKRAPS]

242v at output of fuse in CU L-N
195V at fittings L-N
even the first fitting does not work
there is a two-way switch in the downstairs, no neutrals, just line conductors - this doesn't work for the landing light either

it must be a bad neutral somewhere, the cable is in really good shape, no signs of any degradation (what I can see anyway)

thanks to all

Did you test for voltage between L-E and if you did what voltage was present?

 

[MDJ]

there isn't a dimmer on the first light you tested is there ?

 

[cdavies33]

Whats going on?!? Going to a fault with 50 volts lost and not testing between all conductors and then no IR or continuity tests?

Were you not taught this in your apprenticeship? Fault finding and rectification, spent about half my 3rd year doing it and still struggle with faults in the first few years after that.

Sounds like a break on the feed from the CU and first pendant, I try a long lead method on each conductor back to the CU and see if results are consistent between L-N and slightly higher on E if its wired in twin. If not its hammer out time!

 

[cdavies33]

The chap has probably been putting Christmas decs up and damage something.... lol!

 

[Adam W]

I don't understand your method of testing I'm afraid.
Did you do any other tests apart from checking for voltages?