Hello

I'm about to replace an old timer bathroom extractor fan with a modern one. The old one is fed by a three core and earth cable, the third (yellow) core presumably being the connection to the pull cord switch. I haven't yet been into the loft to check exactly how the wiring was installed.

However, the instructions tell me that the new fan (and light according to the circuit diagram provided) need to be fed via a switched spur with a 3 amp fuse. Double pole switch or plug and socket should be located outside bathroom.

I doubt that the existing installation is via a switched spur (circa 1968), so presumably I need to install a junction box in the loft space to carry the lighting circuit, feed the switched spur from that and then the bathroom light rose from the spur.

The fan presumably is fed with constant live via the ceiling rose with the 3rd core connected to the return terminal from the pull cord switch.

Please confirm and explain what is a double pole switch as opposed to any other.

Ah, England and America, 2 countries divided by a common langauge. A double pole switch has 3 wires going to it, say black, red, and yellow. The black would be the incoming power. In one position it would be connected to the red, and in the other the yellow. Here they are called a single pole, double throw.

Do not confuse with a 2 pole switch. That is one that can connect and disconnect 2 pairs of wires at a time. Inside it has 4 contacts. In one position none of them are in contact. In the other, 2 contacts are connected to each other, and the other 2, to each other.

I am confused by your discription of the old fan. Could it be turned on and off either by the timer or the switch? Or did the fan come on for a timed period when the switch was pulled?

Hello Labman

Fan comes on when light switch is pulled and goes off a predetermined number of minutes after the light switch is pulled again to turn the light off.

Hello again Labman

Didn't realise this forum based in US. You guessed it, I'm UK based. Don't know if your electrical regulations are the same as ours, or indeed whether bathroom electrical fittings are wired up the same way.

Any help you think relevant however would be most welcome.

I have asked a respected local electrician who tells me that our regulations are going overboard. Nothing wrong with simply replacing old fan with new without adding any fused spur etc. Quite safe as it always was. To do any work on light or fan the lighting circuit fuse in fuse box simply has to be removed as I did to remove old fan.