Mysterious Loss Of Continuity....

[Colin Smith]

Hi All,

WC Cloakroom with extractor fan on lighting circuit.

The extractor fan has suddenly stopped working, I suspected it was the fan but found no power on the permanent live feed or the switched live when the light is on. The fan was wired from the cieling rose and I have power there no problem (the light works) and the other end of the cable going to the fan has power.

A continuity check between the ceiling rose and the fan shows an open circuit on all wires, (Earth, switched live, perm live and neutral) suggesting the whole cable has suddenly become severed! The cable run between the rose and fan is behind plaster board and in the ceiling void beneath a tiled floor upstairs, so I can't visualy inspect the cable.

What could be the cause of loss of continuity on all four wires in the cable? I don't have any shorts across the cable either, so no evidence of rodent nibbling and no other work has been done in the vacinity.

Any ideas?

Thanks

 

[Technician]

Hello Colin;  hope this helps.  The method you have used for

testing MAY be the problem so I think a little more detail is

needed.  But yes, it is unusual for all conductors to fail

simultaneously as they appear to have done.

 

[Doc Hudson]

Welcome to the forum Colin. Is this your own property, if it is how long have you lived there, or are you doing this work for someone else? Could there be a 3 pole fan isolator switch located in an obscure location that someone has turned off by accident? A lot of fans are double insulated so some installers do not always carry the earth conductor through.

Doc H.

 

[steptoe]

Is it ELV,?

 

[Colin Smith]

Thank for the replies.

I am now thinking that an isolation switch may be the issue. Basically, I've totally bombed here and forgotton about the fan isolator switch above the door outside, when I go back to check it's going to be off isn't it...??  

 

[kerching]

Thank for the replies.

I am now thinking that an isolation switch may be the issue. Basically, I've totally bombed here and forgotton about the fan isolator switch above the door outside, when I go back to check it's going to be off isn't it...??  

YES!    Like Doc said.

we all make mistakes ( see wife for details!)

i once disembowelled my oven to find out why it didnt work. It was set on auto pilot and wife hadnt cancelled it!.....yet whenever i get called to a cooker the first check is the auto setting, just not at Kerching Towers, WHOOPS

 

[Technician]

You have not "bombed" Colin.  You had a problem, you read the

replies and went away and thought about it. What's wrong with that?

 

[Colin Smith]

You have not "bombed" Colin.  You had a problem, you read the

replies and went away and thought about it. What's wrong with that?

Yep, just felt a bit dumb for missing something obvious but this is clearly a good, friendly forum to which I will certainly return.

Thanks again to you all for the replies and making me feel better!

 

[Technician]

I did something similar to Kerching;  I renewed an oven

element because the markings on the control were worn,

and the oven had top and bottom settings, and when

I saw it the oven was on bottom only so tests revealed an

open circuit to the top element, (as I thought).

 

[NozSpark]

The only thing I can think of is.... If it isn't the isolator switch then is it possible that you could you have got the neutral and switched lives mixed up somewhere?