Cable colours, UK

[pe2dave]

Extractor fan in bathroom. Old one went off with the light, as expected.
new one has a timer.

Red, black and yellow(?) input cable (earth cut short). Original guess was that the yellow was switched live?

With light switched off, no power to any of the wires? Which left me confused.

Vent Axia Silent Fan with Over Run Timer VASF100T is the model. Inputs marked L N SL.

Suggestions please?

 

[AndyPRK]

can you post pictures of the old cable please

 

[pe2dave]

P1001861

• pe2dave
• 26 Aug 2020
• extractor bathroom

Input wiring

As below. House / wiring from 1997.

 

[Bosswhite]

Yellow Wire was loop wire . Live Red , Blue Neutral , Yellow live loop . ( two way lighting etc . )

 

[pe2dave]

Yellow Wire was loop wire . Live Red , Blue Neutral , Yellow live loop . ( two way lighting etc . )

So how to wire the fan please? None are live when light switched off? Yellow / red are live when switched on.

 

[AndyPRK]

so no black wire! a blue wire.

The way to wire the fan is
Red L
Yellow SL
Blue N

But if non are live, you are going to have to find the other end of that cable (the light?) and move the red wire.
or just accept the fan only works with the light on for now

 

[ericmark]

Red was phase 1, Yellow phase 2, blue phase 3 there has never been a colour code for single phase use, in 1997 blue was used as neutral for flex, so would seem likely blue in triple and earth also neutral, and red has always been line so likely red used as permanent line, which leaves yellow as switched line, as @AndyPRK has said.

However there is no colour code, the electrician could have used any colour he wanted, only way is look in the ceiling rose and see where connected that end, normal for ceiling rose a row of 8 terminals, 3 Neutral, 3 permanent line in centre, 2 switched line.

With an opening window a fan is an extra, it does not need a run on, or anything else.

How did you test line? To test line you need to know neutral, a neon screwdriver may show line without neutral but a little hit and miss.

Note:- Both neutral and line (phase) are considered as live, which is why I call it line, but most call it live even if not technically correct.

 

[pe2dave]

Tested with a neon Eric.
I'm happy with red/blue live/neutral.

Is it ok to connect L to N on the fan and leave the Yellow (non) switched disconnected?
Yes, there is a window and we've not had run-on previously.

 

[AndyPRK]

no, as the fan won't run without SL
Just connect all the wires and see what happens

 

[ericmark]

I will guess LS and L will need connecting together and of course N to neutral, it will not work with just L and N connected, it may work with just LS and N connected, but easy way is link between L and LS.

 

[AndyPRK]

I think you need both L and SL but it depends on the manufacture.

OP says both are live and so may as well use those wires

 

[pe2dave]

I think you need both L and SL but it depends on the manufacture.

OP says both are live and so may as well use those wires

Conflicting advice?

Ventaxia -VASF100T - has the 'run on' timer (L wire?).
Guessing SL is used for fan, via timer for run on.

 

[EFLImpudence]

Where were the wires connected on the old fan?

 

[pe2dave]

Where were the wires connected on the old fan?

As expected, Red - Live, Black - Neutral, yellow to sw L (NU on the old fan)

 

[EFLImpudence]

You don't have a Black.

In that case, you need to connect -

Blue to neutral and
Red to BOTH L AND SL.
Yellow still not used.

Or alter the other end of the cable so that the timer can be used.