Discuss Adding a run on timer to an existing fan in the Electrical Tools and Products area at ElectriciansForums.net

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
Is there such a thing?
Job i'm looking at has a bathroom with no window. There is a 230v inline fan in the roofspace, vented from above the shower cubicle to... well... the extraction doesn't go anywhere, but that's another problem.
Taking the grill down I can see the fan, but its screwed to the beam and I cannot access the connections but can reach the T&E supplying it.
The fan just comes on with the lights, neutral at the switch just outside the door.
I've mentioned to the homeowner that the ceiling might have to come down, but he's not keen.

I have seen an add on timer unit for a 12v fan, but not 230
 

Murdoch

Regular EF Member
Messages
25,126
Location
Woking
That says it needs live, switched live and neutral .... and the op thinks he only has switched live and neutral

If the owner can cope with a small variance change the fan for a 12v unit, and mount the transformer / driver near the switch and run a new cable from the switch to the transformer ...
 
OP
littlespark

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
Yes. I’ve only got a sw and n. What I need is the fan to be powered from a timer unit which is triggered by a light switch, not from the light switch itself.
I realise I need a 3 core to operate the timer... but that is straightforward from the switch as there’s a live, sw an neutral there.

Swapping out the fan for a timer version or 12v is impossible without taking down the ceiling.

It may be I could use a humidistat?
 

SparkyChick

Making a banana smoothy for my fave gorilla
Staff member
Moderator
Messages
3,694
Location
South Wales
If you've got permanent live, switched live and neutral at the switch, then that timer would work for you, surely or am I missing something?
 

Murdoch

Regular EF Member
Messages
25,126
Location
Woking
How about a fan with a built in pir ?
 

Taylortwocities

Electrician's Arms
Messages
2,225
Location
Oxfordshire
So much for accessibility:mad:

don’t you love builders (I’m guessing that an electrician would never do this sort of thing…)
 

Murdoch

Regular EF Member
Messages
25,126
Location
Woking
If you've got permanent live, switched live and neutral at the switch, then that timer would work for you, surely or am I missing something?
The way I read it is that he's only got SL and N at the fan and a nice ceiling he doesn't want to cut holes in!
 

Taylortwocities

Electrician's Arms
Messages
2,225
Location
Oxfordshire
How about a fan with a built in pir ?
It’s an in-line fan in the roofspace....
He could add a ceiling PIR..But if he can reach the T&E he still needs to get a permanent live for the PIR.

Whatever the solution for the fan, it still needs venting. I doubt there’s a workable solution without some ceiling carving.
 

SparkyChick

Making a banana smoothy for my fave gorilla
Staff member
Moderator
Messages
3,694
Location
South Wales
The way I read it is that he's only got SL and N at the fan and a nice ceiling he doesn't want to cut holes in!
Absolutely, but none of the solutions are going to work without a permanent live. But he does say this:-

"I realise I need a 3 core to operate the timer... but that is straightforward from the switch as there’s a live, sw an neutral there."

It's obviously impossible to say without being there, but from how it's been described, it doable.
 

Murdoch

Regular EF Member
Messages
25,126
Location
Woking
Ceiling down, do the fan properly .............. thats the price to pay for the customer to have a proper fan working and venting outside ....:)
 

Taylortwocities

Electrician's Arms
Messages
2,225
Location
Oxfordshire
I agree SC. If the fan T&E is at the switch, then adding the unit you linked to would be the easiest way.

If it comes from the light fitting, it depends on the light wiring. No problem if there’s a perm live there. Need input from the OP.
 
OP
littlespark

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
I’m trying to convince customer to take down ceiling in bathroom and kitchen for other works.
See my other post in The Arms

It’s not ideal. The fan is inaccessible for maintenance and vents nowhere.

I haven’t checked that link yet SC to see if it’s suitable, but I will.

Edit: just had a look. That unit will do the job fine. Thanks. And not too expensive.
 

Taylortwocities

Electrician's Arms
Messages
2,225
Location
Oxfordshire
If access to the ceiling will be restricted after the works, it may be better to have a surface ceiling fan and not an in-line one. Your customer will have the same problem in a few years time when (and not if) the fan fails.
 

'mr2'gd4u

Regular EF Member
Messages
180
Location
Farnham
While not just tap into the PL going to the switch and run it to fan?? If its in a loft space you'll have everything visible going to and from switch... Or am I missing something.
 
OP
littlespark

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
You've missed something; - flat roof above bathroom. I cant access the fan, but can see it.
The switch is under an attic and I can get access to that, and push a cable through into the roofspace where the fan is.

The flexy duct that comes from the fan and goes nowhere yet could come down into the kitchen and run in a pipe box above the wall units and through an outside wall.
 

'mr2'gd4u

Regular EF Member
Messages
180
Location
Farnham
You've missed something; - flat roof above bathroom. I cant access the fan, but can see it.
The switch is under an attic and I can get access to that, and push a cable through into the roofspace where the fan is.

The flexy duct that comes from the fan and goes nowhere yet could come down into the kitchen and run in a pipe box above the wall units and through an outside wall.
Ahhh. I c, you say you can push a cable from the switch to the roof space. I cant see how difficult it is to access.
 

Murdoch

Regular EF Member
Messages
25,126
Location
Woking
Ahhh. I c, you say you can push a cable from the switch to the roof space. I cant see how difficult it is to access.
I’m still a bit puzzled by the fact he can see the fan but not touch it .... so changing the fan seems out of the question then ...
 
OP
littlespark

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
The light above the shower has the intake vent around it. Taking this down reveals a 100mm hole.
From here I can see the in-line fan screwed to the beams above the ceiling, but cannot access it to get at the connections.
I can pull the cable back to this hole and fit a timer unit to feed the fan, leaving the other lights on the switch wire.
All I need is a perm live from the switch to the timer. Just as easy using a 3 core from the switch to the fan and putting in a 3 pole isolator while I’m there.
The main house has an attic. The bathroom and kitchen are in a flat roofed extension. The switch for the bathroom is in the main house.
 

Taylortwocities

Electrician's Arms
Messages
2,225
Location
Oxfordshire
OK...
You must have a permanent live at the switch.
Just connect a piece of twin&earth from the switch. You'll need perm live and earth.
Poke it to the fan inlet hole. Then grab your existing fan cable. You then have all that you need for the over-run add-on unit. You'll have to decide where (accessible) that you can locate this.

That should sort the over-run issue. The you have the issue of the fan extract pipe, oh yes and what you do when the fan dies.
 
OP
littlespark

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
Update on this.

Added in a FCU before the bathroom switch, back up the wall and mounted a manrose timer unit, 3 core and earth from switch, and t&e from unit to fan.
Lights are on a different t&e from switch.

Works fine, or so I thought. Lights and fan come on with switch, lights go off with switch, fan runs on for set time....

Except. The inlet grill of the fan has a 12v led lamp built into the centre of it. Wired correctly on the lighting side. With the lights on, it works ok. With the switch off, and whether the fan is running or not, this lamp flashes once about every 5 seconds.

Reason? I think it’s getting a back feed from the timer unit back down the switch wire which is making the light flash.
It may be that the transformer for the12v isn’t right. Meaning it’s designed for a halogen lamp rather than LED.
I’ll change that first to a LED driver.
If that doesn’t work, double pole switch in place of light switch. Using the second pole to isolate the timer sw from the lights.


Not asking a question. Just thinking out loud.
 

Taylortwocities

Electrician's Arms
Messages
2,225
Location
Oxfordshire
It may be that the transformer for the12v isn’t right. Meaning it’s designed for a halogen lamp rather than LED.
That will be the reason. Most of the halogen "transformers" don't work unless they have around 20VA on the output, and your LED will be way less than that.

May just be easier to pop a holgen lamp back in there.
 
OP
littlespark

littlespark

Electrician's Arms
Messages
2,404
Location
Scottish Borders
It's been working with an LED in it up til now. Its just adding the timer that has caused a problem.
I'm not actually sure the transformer that's there is original.

Tomorrows job is to wire the kitchen best way I can with limited wall space and more appliances than kitchen units
 

anthonybragg

Electrician's Arms
Messages
4,328
Location
NORTHAMPTON
Yes. I’ve only got a sw and n. What I need is the fan to be powered from a timer unit which is triggered by a light switch, not from the light switch itself.
I realise I need a 3 core to operate the timer... but that is straightforward from the switch as there’s a live, sw an neutral there.

Swapping out the fan for a timer version or 12v is impossible without taking down the ceiling.

It may be I could use a humidistat?
or a PIR unit.
 

Electrician Talk

Top