Fused Spur for a Chimney Hood

[nas301630]

Hello
I am moving some things around in my kitchen and this means that the cooker hood needs to be moved about 100mm. Unfortunately, this means the FCU for the hood is now inaccessible and the chimney part of the hood would partway cover it.

The FCU switch was wired in with 2.5mm T&E on the kitchen socket ring with flex wired into the load leading to the fan. So my builder (who I know shouldn't be touching the electrics but he convinced me it was simple), took the switch off. He connected the two T&E cables together in a choc box and ran another T&E cable into the choc box and wired the other end into the new FCU in the new location. Then in the load of the new FCU, he wired in 2.5mm to go to the new hood (which has now been delivered).

I wanted to check all this out so I got my electric tester pen out. When I hold the pen to the feed live in the new FCU, it lights up. When I turn the FCU switch on, the live wire on the load lights us too so I thought it was all good. However, when I hold the pen tester to the other end of the load live wire (i.e. the end that will into the cooker hood), it doesn't light up. So surely this means that hood won't work if it gets fitted? I don't understand how the live wire at the FCU end can be "live" but the other end isn't? Am I being stupid?

Sorry...

 

[PrenticeBoyofDerry]

You say choc boxes; where are these left as they need to be left in an accessible location. Any new cable buried in wall will likely need 30mA RCD protection if it not already on circuit.
Voltage pens and neon/ test screwdrivers are an unreliable test for this, you need a two pole/probe(GS38) test instrument.

The builder should have completed a minor works certificate to prove their work is compliant and safe.

 

[nas301630]

I now realise I shouldn't have let him touch it and got a proper electrician but when he talked me through it, it seemed to make sense and I can't understand why it doesn't work??

While it may not meet the regulations, in theory should it have worked? I will now need to get an electrician in anyway but I know I won't be able to let it go if I don't know why it didn't work!?!

 

[PrenticeBoyofDerry]

While it may not meet the regulations, in theory should it have worked?

If everything is connected up correctly then my understanding of the configuration you have explained, it should work.
But if you are getting a voltage reading at the supply side at the FCU then at the load side of FCU, but not at the appliance, this could be that the pen is measuring the terminal voltage and the cable is not making good contact within in that terminal, maybe loose or insulation of conductor is trapped in terminal. As I side you really require a two pole probe as the a pen will not allow references to be made between line-neutral, line-CPC/earth and neutral-CPC/earth. So you could have other issues that the pen will not detect.

I will now need to get an electrician in anyway but I know I won't be able to let it go if I don't know why it didn't work!?!

Well hopefully you have a loose conductor or trapped insulation and not a damaged conductor, you could could run the pen a long the route of the cable/flex (if not buried) between the FCU and appliance and see if you have a point where the voltage reading breaks. Also worth checking the fuse!

 

[nas301630]

I've swapped the fuse out as I thought it might be something as simple as that but as usual, it never is!!. Thanks very much for taking the time to answer my query - I will ask the electrician once I can book him to tell me what went wwrong - otherwise it will haunt me forever!!

 

[nas301630]

Re-read your post properly and I realised that I have tried the pen only right at the tip of the wire that goes into the chimney. When I touch the tip of the pen along the rest of the wire it flashes live immediately!! I should have checked this right from the start. This makes me thing that you are bang on with the suggestion that it's just a really poor connection into the hood. Thanks for making me think again about this - I am sure that just tightening up the connection will make this OK - bit embarrassing though!!

 

[PrenticeBoyofDerry]

Don't forget a circuit also needs the neutral to be continuous to work, this is something the pen cannot confirm, you also need an earth (circuit protective conduct) to provide a path to earth in case of a fault to earth, again something that the pen will not confirm. If an error has been made on the line conductor, it is possible that there could also be some on the other conductors. So it really should be confirmed, it is really not satisfactory that your builder has not confirmed and documented this, if it is beyond his scope he should not be touching it. The last test we do as electricians is the functional test , this where you see the fan turn on/off and the lights switch on/off. This is often the only test by the incompetent but seems this test was beyond the builder, so god knows what that makes him?