I live in a mid 60's bungalow with no gas. Heating is oil fired and besides the normal kitchen appliances there is nothing that draws any high current. My mains electricity cables come into the garage from a tube in the floor, up the wall to the master fuse and onto the distribution unit (fuse box). They are both insulated black and about 15mm outer diameter. On several occasions I have noticed these cables are quite warm (not hot) to the touch. This can be at any time day or night but at other times they are cold. The tails to the fuse box are always cold so is the master fuse box. I am a retired auto sparky but am puzzled. Considering there age etc should this be of concern?