Switched live or live?

[Matt42]

Arrggh, please help! I am replacing my in line extractor fan and can't get the wiring right. The input is red/brown and blue (two leads), looks like neutral has been cut right back but the extractor fan has 3 inputs, l, lt, n. I have connected the neutral to neutral and connected live to live I think (might be LT thinking about it now) it only works for a while, i have closed the unit and come down from loft now before i go mad.

Thanks in advance

Matthew

 

[AndyPRK]

Maybe the new one had a timer and the old one didn't ?
Timer ones have 3 wires

 

[333rocky333]

If you only have 1 input that must be either

permanent live, fan used to run 24hour or
a switched live, fan would have switched on/off elsewhere possibly with the light

in that case you would need to link terminals L to LT

How did you use the neutral if you say it was cut back

 

[Robin0577]

Sounds like you have a fan with a built in timer and wiring which is designed for one without. How is the fan controlled? Does it have its own switch or is it supposed to come on with the lights?

If indeed you have a timer fan and wiring for one without, you can bypass the timer section by connecting the live and switched live terminals together.

Too late, must type faster

 

[Matt42]

Previous fan went off after the shower light went off after a while. The earth was cut back before installed i.e. The old fan just used live and neutral.

 

[Matt42]

Just had a look at the unit i threw away and it has three connections i.e. N,S/L, L so Someone must have connected live input to either S/L or L, whats the difference? And is s/l the same as lt

 

[PrenticeBoyofDerry]

What make/model fan have you?
To determine what the colour cores do you would require to do some testing for continuity and voltage.
You say you have three cores coming to the unit, do you not have an earth cable?
You state red/brown core and blue.
Could you please offer more information on the core colours and whether these colours are repeated at the light or switch and if you have an isolator switch?

 

[333rocky333]

If the old fan run on for a while then 3 wires would have been needed

L is permanent live to run the timer after light switched off
S/L would have been the trigger to start the fan from the light
N is neutral

your instructions will say what Lt is but most likely same as s/l or trigger

 

[sparkwright]

Seems odd you describe the old fan as having the run-on facility, with three terminals, but only two wires.

Are you certain the old fan ran for a bit once the light was turned off?

Are you also certain there wasn't a short wire link between two terminals at the old fan?

First thing you need to check;
On both the old and new fan, what voltage is printed on both?
230/240 v and 12 v are typical values, best check both of these before you do anything.

Also have a look round to see if there is a transformer fitted just before the fan. Very doubtful, but could explain why there are only two wires at the fan.

If you can, send photos of the old fan, the new fan, and the wiring.

 

[Gutterball]

i would guess that the cable with the cut back core is a permanent live borrowed from another circuit and goes to L and the other cable is switched/timed live from the light. isolate the circuit at the fuse board and use a multimeter to find the switched live. connect across L&N at fan and switch switch it will beep on continuity when switch closed.

 

[Matt42]

Thanks guys, i need to revisit this tomorrow. It sounds like the 3 wires need to be connected to the three terminals and not just two then. Ill revert with decent info and photos tomorrow. It doesnt help with 2 and 5 year old boys trying to help and climb the loft ladder

 

[PrenticeBoyofDerry]

As previously mentioned, I think a little more investigation is required, if you could inform us of the model/make of old and new fans it would be very helpful, also any pictures of the cables and terminals would be good.
You need to be aware that not all fans are 230V some are 12V and the reason is normally that the location of the fan does not permit 230V to be present there, so it is important that you relay all this information back to us.

 

[333rocky333]

Just to confirm , it appears the post has been edited

It appears to me now it was the EARTH that was cut back unused rather than the neutral

if so Please dont connect that earth to the 3rd fan terminal as it could well damage the unit.

Most fans are double insulated and could explain why it was not connected or cut back

 

[PrenticeBoyofDerry]

Just to confirm , it appears the post has been edited

It appears to me now it was the EARTH that was cut back unused rather than the neutral

if so Please dont connect that earth to the 3rd fan terminal as it could well damage the unit.

Most fans are double insulated and could explain why it was not connected or cut back

Matt42, it does not help editing posts with important information like that, just answer the questions, I did ask about the earth.
Well spotted 333rocky333.

 

[Matt42]

Apologies, i edited and looked at future postings wondering whether i should have put an 'edited' remark that i 'edited' my post. I decided against it having thought i have created enough confusion for the day, sorry if it compounded the confusion even more