electronic wall timer switch

beebaw

i bought a B&Q 7 day electronic wall timer security switch and am a little confused as to how it is wired.
basically there is 3 terminals
1)Live
2)Load... there is a branch off the diagram on the back of this port showing neutral and then extending out into the common of a second switch
3)2-way... again this leads into the L1 of a second switch.

so i take it the common live goes to the live terminal, the neutral on the light circuit goes into the load but if this is the case how do u connect up the live load feed to the lamp? u can hardly connect the live feed to the lamp to the neutral feed to the Load terminal on the switch?

i have attached a pic of the back of the switch below

M cebee

it's battery powered timer by the looks of it with a changeover contact

you just connect to 'live' and 'load' and ignore the 2-way or n/c connection

meercat

agree with m cebee
maybe not battery powered though
might use backfeed through the lamp to power up

M cebee

ya looks like it -not familiar with any of this gear

not great really these days is it? -only compatible with tungsten

indie armada

this is the switch in question, we sell em but ive never wired one up.
have to have a look at the spec in the mornin.

http://www.bgelectrical.co.uk/pdf/New_from_BG_TWE7_2.pdf

beebaw

yea it has a battery backup, ok so if i connect the common live to "LIVE" and the neutral to the "Load" where does the switched live to the lamp go to?

beebaw

sorry, yes that is the exact switch in the link above.

thanks.

M cebee

you don't connect neutral -it's a direct replacement for a 1 or 2-way lightswitch with tungsten load

Irish Fire

beebaw wrote: »

yea it has a battery backup, ok so if i connect the common live to "LIVE" and the neutral to the "Load" where does the switched live to the lamp go to?

You don't use the neutral (not required) Your "live" is live from board and the "load" is to the lamp. This unit does not need a neutral to run. If you look at the picture you've taken the neutral is on the other side of the lamp.

beanie10

+1
Permanent live to live connection, switch live to load connection, bring your own neutral to light. No neutral is needed at the timer which means it is powered by battery which is a pain in the arse.

Irish Fire

beanie10 wrote: »

+1
Permanent live to live connection, switch live to load connection, bring your own neutral to light. No neutral is needed at the timer which means it is powered by battery which is a pain in the arse.

Yep!!!!

Stoner

I'm fairly sure that the battery in these switches is not a back up, it's to remember the switching program, there are plenty of switches and dimmers out there that don't need a neutral sometimes they can be a bit flaky.
I bought a two gang two way X10 unit recently, it was a bitch to fit and did not look great, ended up taking it down, but anything in a switch that does not need a neutral is great for irish houses as we tend not to have the permanent live and neutral at the ceiling rose as the British houses have, this limits us with respect to dimmers and control units, however the X10 unit I have will handle and did handle CFL and higher wattage LEDs.

are you going to use this for security? looks like it might have a use in some landlords stairwells. I stuck on the Marmitek CM15 X10 software to control a few things in my place. So i can turn off some lights etc online so its handy as you can use your phone, you can also program macros to handle timers as well plus you need a PC on to give it web access, but if the PC is off a small central controller remembers everything.

Like the switch there is a central unit that remembers all the programs for the different switches and sockets it links into your pc via a usb cable once you program it and the and tell it the address of the different light modules and socket modules it will remember the times etc, it uses the 220V wiring in your house to send around a signal. It will control up to 255 units (and more if you give them the same address)

I'ts basic enough but might be worth a look if you want more functions and to control them from the one place.

indie armada

according to the lads here in the job, those switches rely on the phase to charge the battery, which is done while the light is on. this is similar to the two wire occupancy detectors. the battery is there to store the programming selection.

Bruthal

indie armada wrote: »

according to the lads here in the job, those switches rely on the phase to charge the battery, which is done while the light is on. this is similar to the two wire occupancy detectors. the battery is there to store the programming selection.

They probably charge when the light is actually off, as in this state there will be 230v across any switch which is open with a bulb in circuit.
This is why there is a minimum 40w load spec on it. If the bulb is blown or not fitted the timer will not get any supply to charge it. With the light actualy on there will be 0v between the live and load terminals so no charging of the timer battery is happening with light on.

The open switch contacts in a lighting circuit can supply 230v to a circuit as long as the circuit impedence is very much higher than the impedence of the bulb itself.

Bruthal

Stoner wrote: »

I'm fairly sure that the battery in these switches is not a back up, it's to remember the switching program, there are plenty of switches and dimmers out there that don't need a neutral sometimes they can be a bit flaky..

The battery likely also powers the timer display etc when the light is actually on, as when its on the live in and live out of the timer will be at the same potential and therefore there will be no way of powering the timer except with the battery. A single live has no real way of powering anything, and with the contacts closed it is just a single live through the timer.

When the light is off the timer circuit is now powered from the open timer contacts which have 230v across them as the live out(load) terminal is now like a neutral via the bulb, as long as the timer circuit is of a relatively high impedence compared to the bulb itself.

Again this is why the timer has a minimum wattage bulb required. Too low a wattage and the bulb impedence is higher and the timer will have less voltage across its circuit when contacts are open as the higher impedence bulb will have some more voltage dropped across it in series with the timer charging/running circuit.

So i would think the battery powers the timer but is kept charged during light off times. It might be different than this though of course.

Bruthal

meercat wrote: »

agree with m cebee
maybe not battery powered though
might use backfeed through the lamp to power up

Yes thats more or less it. Its like a neutral back through the bulb when the light is off (timer contacts open).