Extractor Fan Switching

[SproutsDad]

Hello, can someone please help answer a dilemma that I have with switching of bathroom extractor fans via the switches shown below?

During a major house extension 25 years ago, the electrician fitted these dual switch Fan & Light units, made and supplied to him through an electrical wholesaler.

> How it has worked to date - These have worked really well in being able to separately control the timer fan and light - avoiding the usual scenario of the fan coming on and running in the night when the light is put on.
The Fan switch is sprung and each push / click turns on the fan for the set timer duration - e.g. one push gives 5 mins, two clicks gives 10 mins etc, or multiples of whatever the fan timer is set to..

> Current Problem - All this worked fine until recently, two of the old fans failed and I fitted the following replacements on two of the bathrooms :-

1. Silent Tornado - an excellent fan, but it will only fire up if the Fan switch is pressed and held for exactly 10 seconds, then it works fine for the set timer duration.

2. AirVent Humidistat - this won't work at all from this Fan switch.

See photos of all this below incl the fan isolator switch.

> Your help please - I would really like to keep these switches, they are great. But ............
1) I don't understand how they work in the first place from one click of the switch. and
2) why they now will not fire up the new fans in the way they have for so many years.

Any ideas on this will be much appreciated.
Thanks


THE DUAL SWITCH

FAN ISOLATOR

OLD FAN

NEW FAN-1 - Silent Tornado

NEW FAN-2 - AirVent Humidistat

 

[JohnD]

I'm pretty sure the "fan" switch will be "momentary " switch. Like a bell push, it is only "on" when you press it.

If you change for an ordinary two-gang switch, it will supply the fan on while it is on. The fan that works is presumably a timer fan with a permanent live, and a switched live fed from the switch. The fan that doesn't work might not be, or might be wired wrong.

You need to invest in a multimeter to see what the wires do.

Edit

Oh dear, you bought a humidistat fan.

Is there a separate timer connection box?

 

[SproutsDad]

Oh dear, you bought a humidistat fan.

Is there a separate timer connection box?

Thanks, I know sorry, I should have bought a simple timer fan, my electrician friend said that humidistats can be more trouble than they're worth, incorrectly triggered etc. He says to just turn the humidistat part down/off?

I usually do 'straightforward ' like for like swap installations myself, then get him to check it out. He too was baffled by these press, click switches - which is why I have written in to this forum. I'll get him to check t with a multimeter for any irregularities in the wiring of these new fans. But my query was because as far as I could see I have not wired anything differently on the new fans.
I'll get it checked and come back to you.
Thanks

 

[SFK]

Fan switch is pressed and held for exactly 10 seconds, then it works fine for the set timer duration.

2. AirVent Humidistat - this won't work at all from this Fan switch.

This might be because some fans are designed to not start until they have had power (switched on) for say 30sec or a minute.

This is to stop fan coming on and being noisy if you just pop into bathroom quickly for something.

If your fans have same design likely you momentary switch is not on for long enough.

 

[SproutsDad]

This might be because some fans are designed to not start until they have had power (switched on) for say 30sec or a minute.

Thanks, good suggestion, yes you're right some do have a delayed start.
Could I maybe try the Silent Tornado - the one that normally takes 10 seconds to fire up - wired through the normal light switch to see if that is a designed in feature?

I'm not sure about the AirVent humidistat, but should I try the same with that to see how it behaves??

Thanks.

 

[SFK]

Yes, move the wire that goes to the fan so it is in the same hole as the wire that goes to the light.
Then both light and fan will be on at same time.
I think I see that as yellow wire moved so in same hole as blue wire.