Only getting 17v on a lighting circuit?

[wazzag]

I'm investigating the lighting circuit under the floorboards on the first floor which is the circuit for the ground floor lights. I've opened up a junction box and found that it's just a simple pass through - connections are red to red and black to black. When I measure voltage across them I find only 17v. Why would this be?

 

[PrenticeBoyofDerry]

Was the power on?
Is the meter calibrated?
Why did you perform this investigation/test?
Did you test between line and earth?

 

[wazzag]

Power was on
Meter was tested on the sockets circuiits
I'm looking to spur off for bed lights
There's no Earth on my lighting circuit in my house

I also found that the PD across the breaker for the same circuit is 240v

 

[JohnW2]

Since you have demonstrated that your meter is working satisfactorily, if your ground floor lighting is actually working, the cables going to the JB you've found cannot really be what you think they are. If it is related to the lights circuit, could it perhaps be a join in the cable to a switch? Do you still get the same (17V) reading regardless of whether (all) the groundfloor lights are on or off?

Kind Regards, John

 

[PrenticeBoyofDerry]

There's no Earth on my lighting circuit in my house

But your system does have an earth, find a way to test line to earth by using an earth path and wander lead.

 

[bernardgreen]

I also found that the PD across the breaker for the same circuit is 240v

If the breaker is switched ON ( closed ) then there will be no PD across the breaker if you are measuring between IN and OUT terminals.

If you measure between Neutral and IN and then Neutral and OUT then with the breaker closed ( ON ) both readings will be 240 volt.

Ar ypou siure the breajer is ON, some MCBs have to be pushed right down before they can be turned back ON. The lever can be pushed up and thus the MCB appears to be ON but it is still OFF

 

[JohnW2]

If the breaker is switched ON ( closed ) then there will be no PD across the breaker if you are measuring between IN and OUT terminals.

Although that is true, I suspect (but may be wrong) that the OP did not mean what he actually wrote about 'measuring across the breaker'.

Ar ypou siure the breajer is ON ....

We are, of course, still not certain that this was intended as a live test. However, asuming it was, since this is the ground floor lighting circuit, one imagines that the OP would be aware if the MCB was 'off'.

Kind Regards, John

 

[Echo the husky]

There's no Earth on my lighting circuit in my house

Where are you going to connect the CPCs of your new cables to?