Broke some fins on bathroom extractor fan

grumbler

I don't know how this can be possible if the fan is activated but the light switch.

I.e. if it's independent it disconnects only one out of two live wires coming to the fan and you can easily forget to switch the lights (and hence the second live wire) off when repairing the fan.

coffeehound

grumbler said:

I don't know how this can be possible if the fan is activated but the light switch.

I see what you mean - two lives.  Perhaps a sparks can confirm?

Swasterix

grumbler said:

Swasterix said:

grumbler said:

coffeehound said:

Hasn't it got an isolating switch?  Should have..

The switch often operates both the fan and the bathroom lights.

Well yes, but I think Coffeehound is referring to the fact that it should have an isolator independent to the light switch. 

Why independent? If the fan (with a timer) is activated by switching the light on, then the isolator switch switches both the light and the fan off. At least that's how it works in my house.

It's separate because

1. it's 'isolator', i.e. disconnects both live and neutral
2. a fan with timer has to keep working when you switch the light off

Actually no. A fan with a run on timer usually has both a live and switched live connection. Your light switch controls the switched live, and doesn’t completely isolate the fan or the light fitting. 

Edit to add/ the switched live allows it to be controlled on/off with the light switch. The permanent live allows it to run on once the light switch is turned off. 

Like so;

coffeehound

Blimey, there's a lot going on in that ceiling rose!

grumbler

Swasterix said:

grumbler said:

Swasterix said:

grumbler said:

coffeehound said:

Hasn't it got an isolating switch?  Should have..

The switch often operates both the fan and the bathroom lights.

Well yes, but I think Coffeehound is referring to the fact that it should have an isolator independent to the light switch. 

Why independent? If the fan (with a timer) is activated by switching the light on, then the isolator switch switches both the light and the fan off. At least that's how it works in my house.

It's separate because

1. it's 'isolator', i.e. disconnects both live and neutral
2. a fan with timer has to keep working when you switch the light off

Actually no. A fan with a run on timer usually has both a live and switched live connection. Your light switch controls the switched live, and doesn’t completely isolate the fan or the light fitting. 

Edit to add/ the switched live allows it to be controlled on/off with the light switch. The permanent live allows it to run on once the light switch is turned off. 

Like so;

Thanks, this does make sense.

However, in my house (c. 1995) it's a simpler two-pole isolator, not three-pole. And I've never said that the light switch completely isolated anything. Quite the opposite.

Swasterix

coffeehound said:

Blimey, there's a lot going on in that ceiling rose!

Or a junction box 😁

Swasterix

grumbler said:

Swasterix said:

grumbler said:

Swasterix said:

grumbler said:

coffeehound said:

Hasn't it got an isolating switch?  Should have..

The switch often operates both the fan and the bathroom lights.

Well yes, but I think Coffeehound is referring to the fact that it should have an isolator independent to the light switch. 

Why independent? If the fan (with a timer) is activated by switching the light on, then the isolator switch switches both the light and the fan off. At least that's how it works in my house.

It's separate because

1. it's 'isolator', i.e. disconnects both live and neutral
2. a fan with timer has to keep working when you switch the light off

Actually no. A fan with a run on timer usually has both a live and switched live connection. Your light switch controls the switched live, and doesn’t completely isolate the fan or the light fitting. 

Edit to add/ the switched live allows it to be controlled on/off with the light switch. The permanent live allows it to run on once the light switch is turned off. 

Like so;

Thanks, this does make sense.

However, in my house (c. 1995) it's a simpler two-pole isolator, not three-pole. And I've never said that the light switch completely isolated anything. Quite the opposite.

Apologies if that’s the case, I must have misinterpreted what you’d said!

Obviously I’m not saying that’s how they’re always wired up. But if you asked an electrician to fit one today, that’s how they would (or should) do it. 

Even having said all of this, I’d still isolate the lighting circuit in the consumer unit before working on the fan! Can never be too careful and I never trust that things have been done properly. 

Grenage

Yes, they are supposed to be wired so that you can completely isolate the extractor (independent of the light) , that's how I did it in my last house.  More often than not, they aren't.

grumbler

Grenage said:

More often than not, they aren't.

I don't think so. Even in my case with a 2-pole switch they are.

Grenage

grumbler said:

Grenage said:

More often than not, they aren't.

I don't think so. Even in my case with a 2-pole switch they are.

But one would ideally want to isolate the live, switched live, and the neutral.