Bathroom SELV extractor operation

[wingit]

I'm planning on getting a Vent Axia SELV Humidistat-Timer HT IPX7 extractor fitted in the bathroom.

It will be switched by a 12V light switch at the wall, not by pull cord, the switch will only operate the fan, not the lights.

It will not run in trickle mode, only switched on and off at the wall. The issue is that because it has a humidistat I'm concerned that someone could leave the fan in full on mode all day thinking it was just in humidistat mode and expecting to turn itself off. The switch itself is a special wafer switch and has already been purchased, it does not have any way to know by looking at it if it is on or off.

Basically I just want a fan that ideally has a humidistat, and allows to be controlled exclusively by a wall switch, where the operator can know if the switch is activated or not.

I've attached the wiring diagram for the option I plan to use.

The instructions http://www.vent-axia.com/files/pdf-downloads/F&W Instructions (2)_1.pdf did not enlighten me either.

Cheers

 

[ban-all-sheds]

It will be switched by a 12V light switch at the wall

1) That is unusual. Have you found a suitable switch which can be mounted where you want?
2) It's not what the instructions show.

The issue is that because it has a humidistat I'm concerned that someone could leave the fan in full on mode all day thinking it was just in humidistat mode and expecting to turn itself off.

OTOH, if you cut the supply to the fan, won't it just stop instantly?

The switch itself is a special wafer switch and has already been purchased

What's the IP rating?

Basically I just want a fan that ideally has a humidistat, and allows to be controlled exclusively by a wall switch

What do you mean?

I've attached the wiring diagram for the option I plan to use.

No you haven't.

Whether the wiring diagram does not implement your plan as stated, or whether what you say about your plan is wrong I don't know, but the two don't match - there's no 12V switching in the diagram.

 

[wingit]

1) That is unusual. Have you found a suitable switch which can be mounted where you want?
2) It's not what the instructions show.

Yes, I've found the switch, here at this website http://www.electronicsarena.co.uk/c...-bathroom-switch-double-plate-2-button-dimmer
It's suitable for zone 2.

OTOH, if you cut the supply to the fan, won't it just stop instantly?

I don't know, that's what I'm trying to determine

No you haven't.
Whether the wiring diagram does not implement your plan as stated, or whether what you say about your plan is wrong I don't know, but the two don't match - there's no 12V switching in the diagram.

I should have said that the wiring diagram was from the fan manufacturer for connecting the fan in the mode that I want, it does not include the 12V light switch connection, but I think that 12V or 240V doesn't change the nature of the question.

What do you mean?

I mean that I want to operate the fan like a pull cord operation but by the wall switch.

 

[PrenticeBoyofDerry]

What is your reasoning behind using a dimmer switch to control an extractor fan?
What is your reasoning behind not using a simple fan isolator switch to disconnect supply?
Does this circuit have 30mA RCD protection?
And what bathroom zones are you installing in?

 

[ban-all-sheds]

Yes, I've found the switch, here at this website http://www.electronicsarena.co.uk/c...-bathroom-switch-double-plate-2-button-dimmer

That's a 2-gang dimmer.

It's suitable for zone 2.

It's not suitable for your fan. Or indeed possibly anything except the LED driver it is designed to control. Hopefully you can return it - I don't suppose it was cheap.

OTOH, if you cut the supply to the fan, won't it just stop instantly?

I don't know, that's what I'm trying to determine

OK - put it another way - if you don't provide the fan with any electricity, what will keep it running?

I should have said that the wiring diagram was from the fan manufacturer for connecting the fan in the mode that I want, it does not include the 12V light switch connection,

Because you can't have one.

I mean that I want to operate the fan like a pull cord operation but by the wall switch.

Then use a wall switch instead of a pull cord switch, as long as it is suitable for the location, and don't bother buying a continuous extract fan or one with a humidistat.

What's your objection to using a pull cord switch? How is the lighting controlled?

 

[ban-all-sheds]

Oh - BTW:

The switch itself is a special wafer switch

http://images.google.com/images?q=wafer+switch

 

[flameport]

Wiring for the 12v switch: http://altima.co.uk/DbFiles/File_10620_pdffile.pdf
Operates a remote controller device which switches 240V. Can be used for many different types of lighting and also a fan.

Therefore what was the question?

 

[wingit]

That's a 2-gang dimmer.

Because you can't have one.

Yes, the name is a little confusing, I have spoken with the manufacturer and it is suitable to control fans and/or lighting, with the supplied transformer

OK - put it another way - if you don't provide the fan with any electricity, what will keep it running?

Currently there is an IPX4 240V fan in place, which runs continuously on trickle with humidistat boost and switched on to boost with the LED lights by the same 12V switch.
My electrical knowledge is a bit limited, but my understanding is it has a live connection to run in trickle mode, then switched live by the 12V switch to full power.
So, I imagine that with the humidistat function the SELV fan would be powered in the same way as it has a live connection, turning itself on as necessary to reduce humidity, and switched live by the user as and when needed. But the problem as I understand it is that when the fan is on, I would not know if it was on by humidistat (which would soon turn off by itself) or on by the switch, in which case it would run until switched off.

Then use a wall switch instead of a pull cord switch, as long as it is suitable for the location, and don't bother buying a continuous extract fan or one with a humidistat.

What's your objection to using a pull cord switch? How is the lighting controlled?

The lighting is controlled by the same 12V wall 'dimmer'.
Regarding pull cords, the wife doesn't like them :/ .
I might just have to get a fan without trickle, which is absolutely fine, and without humidistat, which is OK, but it would be preferable to have it.

Cheers.

 

[wingit]

Oh - BTW:


http://images.google.com/images?q=wafer+switch

Yeah I googled that too, hehe, doesn't look the same at all. Dunno, why Altima call them that.

 

[wingit]

What is your reasoning behind using a dimmer switch to control an extractor fan?

It's actually not just a dimmer switch, it's an on/off switch, the requirement is a fan operated as needed like a pull cord operated one, but by a wall switch instead.

What is your reasoning behind not using a simple fan isolator switch to disconnect supply?

There is an isolator switch but it's way above the door and out of reach of the wife, so she cannot switch it off as needed.

Does this circuit have 30mA RCD protection?

Yes.

And what bathroom zones are you installing in?

Zone 2.

 

[wingit]

Wiring for the 12v switch: http://altima.co.uk/DbFiles/File_10620_pdffile.pdf
Operates a remote controller device which switches 240V. Can be used for many different types of lighting and also a fan.

Therefore what was the question?

My requirement is for the fan to be switched on and off at the wall switch, like with a pull cord, but at the wall switch. But the switch only controls the fan, not the lights, the lights are turned on by another button. My concern/confusion is that the fan I want to get has a humidistat, so if the fan is on, I won't know if it is on by humidistat or on by the switch, which could be an issue if I go out and leave it on all day thinking it's only on temporarily. I'm not sure if I'm thinking about this in the right way, so explaining it on the forum is helping me to clarify and understand the problem (or if one even exists).

 

[wingit]

I think my current best options so far are:

1) Have a fan that does not have a humidistat, then it won't come on automatically for any reason, only when the wall button is pressed, no ambiguity as to why it is on.
2) Have a fan with humidistat and have an additional LED down light fitted that is controlled by the same wall switch as the fan, so if it's on by the wall switch then the dedicated light for the fan is on, otherwise if it's on overrun(?) or humidistat the additional light on not on.

It's been helpful to explain the setup to you good folks on here as it has helped me clarify the options but if you come up with any additional ideas that would great ..

 

[flameport]

My concern/confusion is that the fan I want to get has a humidistat, so if the fan is on, I won't know if it is on by humidistat or on by the switch

If using the diagram posted initially then if the switch is off, the fan doesn't work.
With the switch on, it only extracts when the humidity is above a certain level, then switches off when the humidity reduces.
Fans of this type are generally left switched on all the time so they will automatically operate when required.

 

[wingit]

My concern/confusion is that the fan I want to get has a humidistat, so if the fan is on, I won't know if it is on by humidistat or on by the switch

If using the diagram posted initially then if the switch is off, the fan doesn't work.
With the switch on, it only extracts when the humidity is above a certain level, then switches off when the humidity reduces.
Fans of this type are generally left switched on all the time so they will automatically operate when required.

Ohh, I see, thanks.. That makes me wonder if the 12 controller that switches to 240V would be safe to be left on continuously. It would also negate the reason to even have a switch. The final problem would be if the room needed extraction for a reason other than humidity, like toilet smells, according to your description, pressing the button would not force it to turn on. I'm not sure if I'm wiser now, or more confused

 

[flameport]

That makes me wonder if the 12 controller that switches to 240V would be safe to be left on continuously.

That's what they are designed for.

Fans of that type are usually also wired to the lighting, so that when the light is on, the fan runs regardless of humidity, and continues to run when the light is off for a few minutes due to the adjustable timer.
At any time if the humidity level is too high, the fan will operate regardless of the timer or lights.

Humidity sensors are often more trouble than they are worth, as humidity varies due to the weather and time of year.
It's also unlikely that an expensive SELV fan is required anyway, and given that the controller is usually fitted into the loft, an inline extractor would be a much better option.