Help with relay wiring

[Electricity Forum/ Grt11]

Hi, I want to wire in a timer switch to a bathroom extractor fan. The extractor fan is currently wired to the light switch or more specifically line on the ceiling rose terminal.

I would like to keep the fan coming on with the lights and have an additional timer switch on the wall next to the light switch that a person can press after a shower or bath and extraction will work for 15mins more with the light being able to be switched off. Currently I need to go back and manually turn the light off which is a pain.

The fan did not come with a timer and with a blank page to work from I prefer the idea of it not being an automatic timer that way if someone is using the bathroom for a minute or so the fan doesn't need to come on for 15 minutes.

I can't find any products with a quickly adjustable timer dial to mount on the wall and don't think that's the best solution anyway. Perhaps a humidity sensor would be the most hassle free however I've decided to go with the Elkay 3 wire master timer pushbutton switch and will set it for 15mins.

Can anyone advise if its acceptable to use a relay in a lighting circuit, best practise for mounting and if the below picture would work?
I'd have one switched live going to com 1 on first relay and the other switched live from timer going to com 1on second relay. Just imagine the light in the picture is swapped for the extractor fan.
The only thing that concerns me is if the light is on and someone presses the timer then both normally open contacts would come on and would that cause any problems? Would electricity travel from 1 relay to the other and towards the opposing switch? I assume it would but can this cause overheating or likewise.

The other thing is all the live feeds will be coming from the lighting circuit but does this then become two separate circuits or is it still classed as the same circuit?

I want this to work so any suggestions would be good and it needs to be this setup unless there is a different electrical component that can be used instead of a relay?

Thanks.

 

[littlespark]

This can be done with standard timer fans.

Have a second switch that doesn’t operate any light… but is the sw of the fan. This triggers the fan to run, the permanent live to the fan keeps the timer going.
Feed the second switch off the output of the first (light) switch…. So you can have light without fan.

 

[Electricity Forum/ Grt11]

This can be done with standard timer fans.

Have a second switch that doesn’t operate any light… but is the sw of the fan. This triggers the fan to run, the permanent live to the fan keeps the timer going.
Feed the second switch off the output of the first (light) switch…. So you can have light without fan.

Hi,

I think you may have saved me a lot of time and some expenditure on relays too!

So I don't want light without fan I always want light and fan to run together.

If I'm following you right though I just take the permanent live from existing light switch and connect that to timer switch which will be in a wall box right next to existing light switch.

Then switched live from timer switch goes via existing junction box in loft which connects switched live from ceiling rose to fan.

So when light switch is pressed fan comes on.
When only the timer switch is pressed fan comes on but no light as light switch will be off.
And if lights are on and timer is pressed then lights switched off timer will still run its allocated minutes then go off and no adverse conditions as all the same circuit?

Sounds perfect.

Thanks!

 

[Electricity Forum/ Grt11]

Hi,

I think you may have saved me a lot of time and some expenditure on relays too!

So I don't want light without fan I always want light and fan to run together.

If I'm following you right though I just take the permanent live from existing light switch and connect that to timer switch which will be in a wall box right next to existing light switch.

Then switched live from timer switch goes via existing junction box in loft which connects switched live from ceiling rose to fan.

So when light switch is pressed fan comes on.
When only the timer switch is pressed fan comes on but no light as light switch will be off.
And if lights are on and timer is pressed then lights switched off timer will still run its allocated minutes then go off and no adverse conditions as all the same circuit?

Sounds perfect.

Thanks!

I've spotted an error in my working. If light is switched off and independent timer switch is pressed it will still be connected via junction box to ceiling rose to line connection which will turn on the light.

I don't think I can have two sets of wires running into fan either as the same thing would happen, it would energise light circuit.

Am I still going wrong somewhere or is a different setup or relay needed? Thanks.

 

[littlespark]

Ok. The way a timer fan works is that it needs a switch wire to bring it on… that can be the light or another switch. (With light is normal)
When the switch is turned off, the timer part of the fan runs, taking power from a permanent live… which you will have if there’s a joint box.

So normally, if the light is on, the fan is on. When the light is off, the fan continues to run until timer expires.

My two switch suggestion was if you wanted the fan without a light, or indeed, light without the fan, although I know it’s not always easy to get a second switch wire from a switch.