Two-way lighting

[Andrew Millne]

I am currently in the middle of decorating one of my bedrooms and thought now would be a good time to start testing the water with an Idratek install.

I would like to swap over the original light switch with a DRB module in order to switch the lighting however this room also has a two-way pull cord switch I don't wish to lose. The wiring to the pull switch is by no means easy to access.

What is the best way to approach two-way lighting using idratek modules in a retro-fit situation?

[Viv]

Two way switching within the Cortex is in effect achieved by software. That is you can turn any light on/off (Idratek relay) from any location (Idratek buttons).

If you want to ADD Idratek/Cortex automation to an existing manual lighting circuit and retain the manual wiring then you wire one of the relay modules switching contacts across the light switch (i.e. in parallel). This allows Cortex to turn on/off the lights automatically or alternatively you can still use you manual switch. Note however that if either the manual system or the automated system are turning on the lights then the other method cannot turn them off.

You can add automation to an existing manual two (or greater) way lighting circuit. You will normally see three active wires between the switches. If you look at one of the two way switches you will typically see a common connection and the two changeover connections perhaps marked L1 and L2. The Switch internally connects the connection from the common to either the L1 or the L2 connection. To add the automation you connect an Idratek relay across the L1 and L2 connections. This means when the Idratek relay is operated it shorts together the L1 and L2 connections.

This will mean you can turn the lights on/off via automation or use EITHER of the existing manual two way switches to turn the lights on/off. Again however if either of the systems are switching the light on the other method cannot turn the off.

Viv

[Andrew Millne]

Thanks Viv for that detailed reply. At the moment I'm thinking of using a drb-001 at the wall switch to switch the light and then connecting the pull cord to one of the external switch inputs on the DRB and like you say switch in software. Would this be an appropriate solution (and possible in cortex) to maintain each switches operation of the light independantly? Effectively toggling the relay state when the state of the input (the pull cord) is changed?

[Kevin]

The big issue here is that you need to be assured that the pull switch can be isolated from the mains in every aspect (L E and N) and chances are it can't. The reason is that Live will feed in one end of the 2 (n) way switching circuit and at the other end it will come out 'switched' and feeds the light bulb. Thus at any time one of the two wires L1 or L2 needs to carry live 230V mains. Which one of these two L1/L2 depends on the two way switching, so both can become live alternately. The light and the bulb feed will be usually at opposite ends of a 2 (n) way circuit. However if your pull switch is attached by 3 wires (+ Earth) , and as a spur to the wall switch then you're fortunate . You're toast probably lands butter side up too ;-)

If behind the switch where you are installing the DRB you happen to have Live and also the switched Live to the bulb then you might be lucky. If you can isolate all the wiring to the pull switch from the existing wall switch and still control the light you stand a chance. I must make the obvious warning that mains can kill, and incorrect wiring can cause fires so if you're in any doubt get a sparkie.

I would however still strongly caution against this (wiring a remote switch over deprecated mains wiring) as it is almost impossible to know where the wires go and if there are other T's off the wiring or loops that are dependent on this continuity then you have serious problems. Thus you can never know the circuit to the pull switch is truly isolated , or by its absence you have not impacted something else eg earthing, or a neutral path It's likely even to be against current regulations based on the risk that someone mistakenly later attaches to your cable some mains power and then 'bang'.

One possible solution if the live feed starts at the pull switch end, and if you have neutral available at the wall switch is using a small mains relay behind the DRB and using 1 wire from the pull switch eg L1 as a permanent required live feed and the second L2 as a switched live from the pull switch which would toggle the relay. Then the isolated contacts on the relay feed your input to the DRB. I think a sparkie may be required to do this under the new Part P regulations.

Kevin