Omnipolar Switch???

[liam546]

I am looking to fit an inline extractor fan and the instructions say 'must have an Omnipolar switch with a contact separation of at least 3mm, the circuit must be protected by either 3Amp fuse or suitable MCB'

I was told by an friend who knows a bit about electrics to run a 3 core cable off the live (which is my switch) to an isolator switch just outside bathroom and then 3 core to the fan.

Is this Omnipolar switch it refers to in fact my isolator switch I plan to wire in anyway?

 

[EFLImpudence]

Could be. Omni means 'all'.

 

[aesmith]

Could be. Omni means 'all'.

Meaning switching all three poles in this case?

 

[EFLImpudence]

Could be. Omni means 'all'.

Meaning switching all three poles in this case?

Probably but we don't actually know.

If the fan does not have a timer then it will only be two.
If it does have a timer then there are wiring methods of isolating all three with a two-pole switch.
Hence the manufacturer's sensible use of 'omni'.

 

[AndyPRK]

Or three pole switch

 

[ericmark]

As already explained there are a variety of methods to wire in a fan. Part F building regulations say when it is required and how it must be switched.

Where it is required by regulations not just something you fancy having if there is a window, your not allowed to use lights as the sole way to operate the fan, although you can use it as one method.

Having two switches means using double pole light switches and often a double pole fused connection unit.

But with just the light switch working the fan then a three pole isolator is more common method.

Some fans have a delay timer but the other method is to use a pneumatic delay push switch again meaning different way to wire. There is no requirement to have it connected to the lights this is often done to ensure people use the fan but it is not required the rules assume people can be simply told to push the button.

Again using a PIR there is often a delay feature built into the PIR so no need to have one also built into the fan.

In a bathroom one could use a humidity switch but where there is also a water closet again a second method is also required.

Where the window can be opened there is no requirement for a fan so it can be wired any way you like.

There does seem to be a move towards heat exchangers rather than simple fans however I have not heard of anyone to date being forced to fit the system.

In real terms often LABC says you must fit a fan but as soon as they go it is turned off so there are many sold which will likely only get used 5 times.

 

[liam546]

Thank you for all replies.

The fan is an manrose fan and I will be using the timer option. I want to the fan to work off the light and stay on for 30 secs after I leave bathroom. I also want an isolator switch on outside if bathroom to cut out the fan if I wish before the 30 secs is up.

So where it says I must use an Omnipolar switch, do you think this means I need a switch that cuts off all three wires of the 3 core cable, I.e (3 pole isolator switch)

I have run 3 core from light switch to isolator switch, then 3 core to fan so far. But haven't wired anything

 

[EFLImpudence]

So where it says I must use an Omnipolar switch, do you think this means I need a switch that cuts off all three wires of the 3 core cable, I.e (3 pole isolator switch)

Yes.

I have run 3 core from light switch to isolator switch, then 3 core to fan so far. But haven't wired anything

Do you have a neutral at the switch?

 

[liam546]

I have a neutral in a connector block in the light switch

 

[EFLImpudence]

That's lucky. Good to go, then.

 

[ericmark]

Will be wired something like shown here.

 

[EFLImpudence]

No. He has a neutral at the switch so it's just a single run from switch to isolator to fan.

As I have said before, I think the style of your diagrams will completely bamboozle a DIYer but that one is not representative of the situation.

 

[phatboy]

30 second over run? That's going to be pointless. I would have at the very least a 15 minute over run once the lights are turned off. You need the fan to remove as much wet air as possible, or as much smelly air in the case of using the toilet!

If you need to turn it off early for any reason, just turn the isolator switch off and back on again.

 

[AndyPRK]

yes 30 secs is pointless.

You want a couple of minutes for toilet
and 10-15 mins for shower.

What with such a difference in requirement I fitted one with a humidiy sensor built in, which works well once adjusted.

 

[ericmark]

Part F does stipulate the run over. As to diagram no longer have software installed so not making another one but nothing to stop anyone else doing it.