Timed Extractor Fan

wardle

Hi

Have recently had a downstairs bathroom built as part of an extension. Initially only had it finished to first fix. Electrical work was done to provide a light (switched) and an isolation switch for extractor fan, cabling for fan was in place but fan not installed.

Bathroom is now fully fitted and I tried installing fan last night with a peculiarly outcome!

It's a timed fan (no humidity or pir sensors) so has P live, S live and N. 3 core cable already in place from isolation switched so I hooked it up.

First attempt the fan came on as soon as power was restored and stayed on whether light was on or off.

Thinking I had the P and S lives wrong way round...Second attempt when power goes back on fan pulses on/off as does light, whether light switch is on or off!

This has me confused, any help much appreciated. Presume it's a misconnection between light switch and light?

For info, the input to isolation from the light has 2 brown wires to L1 terminal, 2 blue to L2 and brown to N. the sparks colour coding doesn't seem to be particularly helpful!

Thanks

aido79

wardle wrote: »

Hi

Have recently had a downstairs bathroom built as part of an extension. Initially only had it finished to first fix. Electrical work was done to provide a light (switched) and an isolation switch for extractor fan, cabling for fan was in place but fan not installed.

Bathroom is now fully fitted and I tried installing fan last night with a peculiarly outcome!

It's a timed fan (no humidity or pir sensors) so has P live, S live and N. 3 core cable already in place from isolation switched so I hooked it up.

First attempt the fan came on as soon as power was restored and stayed on whether light was on or off.

Thinking I had the P and S lives wrong way round...Second attempt when power goes back on fan pulses on/off as does light, whether light switch is on or off!

This has me confused, any help much appreciated. Presume it's a misconnection between light switch and light?

For info, the input to isolation from the light has 2 brown wires to L1 terminal, 2 blue to L2 and brown to N. the sparks colour coding doesn't seem to be particularly helpful!

Thanks

A timed fan is designed to stay on for a period of time after the light has been switched off. That's the whole idea of it.

wardle

aido79 wrote: »

A timed fan is designed to stay on for a period of time after the light has been switched off. That's the whole idea of it.

Sorry, you misunderstood. The fan doesn't come on with the light, it comes on when the light is switched off, and then stays on. I.e it's doing the opposite of what it should do (but is not automatically turning off)

2011

wardle wrote: »

Sorry, you misunderstood. The fan doesn't come on with the light, it comes on when the light is switched off, and then stays on. I.e it's doing the opposite of what it should do (but is not automatically turning off)

Most likely there is a wiring mistake at the light switch. The switch wire for the light should be connected to the switch wire for the fan. That way they switch on together.

wardle

2011 wrote: »

Most likely there is a wiring mistake at the light switch. The switch wire for the light should be connected to the switch wire for the fan. That way they switch on together.

Thanks. I looked at it again last night. Switch only has a single N and L (no other lights on this loop) but I think the complication is in the JB as the fan isolator has 2 wires going to a L1 and 2 more to a L2, as well as a N. Might just need to get a sparks out. Cheers

hufpc8w3adnk65

wardle wrote: »

Thanks. I looked at it again last night. Switch only has a single N and L (no other lights on this loop) but I think the complication is in the JB as the fan isolator has 2 wires going to a L1 and 2 more to a L2, as well as a N. Might just need to get a sparks out. Cheers

Sounds like a total botched job... switchs shouldn't have neutrals at them. Get a REC to come sort out as you say is the best bet

wardle

MrMac84 wrote: »

Sounds like a total botched job... switchs shouldn't have neutrals at them. Get a REC to come sort out as you say is the best bet

Sorry my mistake, it's a L1 and common live at switch, not N

aido79

wardle wrote: »

Sorry, you misunderstood. The fan doesn't come on with the light, it comes on when the light is switched off, and then stays on. I.e it's doing the opposite of what it should do (but is not automatically turning off)

Yes you're right I did misunderstand.
It seems like the problem is at the isolator switch. You need to put the 2 blues in the N terminal and the single brown in L2.

wardle

aido79 wrote: »

Yes you're right I did misunderstand.
It seems like the problem is at the isolator switch. You need to put the 2 blues in the N terminal and the single brown in L2.

Thanks

That's assuming they're colour coded right I presume! What's the risks with getting it wrong?!

Cheers

aido79

wardle wrote: »

Thanks

That's assuming they're colour coded right I presume! What's the risks with getting it wrong?!

Cheers

I don't suppose you have a multimeter so you can check which is live and which is neutral?

I would imagine anything that could go wrong would have already gone wrong by having the neutral and permanent live going to the wrong terminals.

wardle

aido79 wrote: »

I don't suppose you have a multimeter so you can check which is live and which is neutral?

I would imagine anything that could go wrong would have already gone wrong by having the neutral and permanent live going to the wrong terminals.

No but might be able to get hold of one.

TBH it's all new wiring / board etc so should all be sound enough. My main worry on the coding of wires was the fact that at isolator both the live and neutral are brown which surprised me as it is all new and fully certified.

Thanks for the help, will report back once I get chance to try at the weekend

wardle

aido79 wrote: »

Yes you're right I did misunderstand.
It seems like the problem is at the isolator switch. You need to put the 2 blues in the N terminal and the single brown in L2.

Genius! Cheers Aido, that worked a treat