Greetings,

Is it a good practice to remove the sheathing on NM/twin & earth cable to run them through a conduit on house wiring?
I'm just curious because the contractor which installed my house stripped the white cover or sheathing of twin & earth cable.
The thing is, when we switch on other lights in the house, the is a strange inference on TV. I phone the contractor and notified them, but hey said I must replace the LED lights with normal energy saver or incandescent bulbs.

We did as they said and is working. But I wonder why the wiring doesn't allow LED lights on other rooms, whereas the same LED work fine on other rooms?

Please help and thank you in advance.