General: Adding a PIR switch

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- CommentAuthorRex
- CommentTimeDec 26th 2020
Ho Ho Ho one and all,

Just making a general enquiry; not ab out to actually do the work myself!!! (yet)

When we built, we have a cupboard space that was to be a 'walk-in' pantry. It is next to the corridor to the utility room. At the time, one light was ceiling mounted to illuminate the corridor and pantry. Then we decided to fit doors to the pantry, and I added and extension light so the one switch turns on both lights (corridor and pantry.)

What would be nice is for the switch to continue to activate the corridor light, but have the pantry light on a PIR switch, only activated when one enters the pantry.

How possible is this without accessing all the wiring, which would be difficult and cause unnecessary mess?
- CommentAuthordjh
- CommentTimeDec 26th 2020
Posted By: RexWhat would be nice is for the switch to continue to activate the corridor light, but have the pantry light on a PIR switch, only activated when one enters the pantry.

How possible is this without accessing all the wiring, which would be difficult and cause unnecessary mess?

Impossible to know for sure because it depends on the existing wiring. Is there live mains at the pantry light fitting even when the light is off? If so, then you can connect the PIR between it and the light - more detail once specifics are confirmed. If not then either (a) route live mains to it somehow (may be a spare wire somewhere?) or (b) connect the PIR between the switched live and the pantry light. In case (b) the light will only come on if you've already turned the corridor light on, which may not be what you want.
- CommentAuthorEd Davies
- CommentTimeDec 26th 2020
As the light in the pantry was added later (when the door(s?) were added) I assume there's a switched line to the pantry light from wherever the lighting in the corridor is looped - presumably either the corridor light switch or the corridor light fitting. Either way, there ought to be a permanent line there which the line wire to the pantry can be moved on to.

The one plausible combination which would snooker you would be if the loop in/out for the existing is at the corridor light switch but the pantry light is fed from the corridor light fitting. In that case there wouldn't be a permanent line available easily.

This is the sort of situation when one might wish one had done “home-run” wiring with all switches and fittings taken back to one of a small number of wiring cupboards.
- CommentAuthorWillInAberdeen
- CommentTimeDec 26th 2020
No need to mess with the mains wiring - do it with a 'smart' bulb and connect a PIR wirelessly.

I seem to recall a smart bulb with a built-in PIR but don't remember where.
- CommentAuthorEd Davies
- CommentTimeDec 26th 2020
We need to be clear if the pantry light is wanted when the corridor light is off, or not.
- CommentAuthorRex
- CommentTimeDec 26th 2020
Gentlemen,

Thanks for the comments. Yes, I would like the pantry light to be PIR active when the corridor light is off.

The corridor light would be switched, the pantry always activated by the PIR; assume that means the pantry PIR has to have a permanent live mains

Am just making initial enquiries, but how do I check if the pantry light has an active live? I do have one of those current battery operated detectors; would waving that around the pantry light when it is off, tell me if the live side is live?
- CommentAuthorEd Davies
- CommentTimeDec 26th 2020
Posted By: Rex…but how do I check if the pantry light has an active live?
It's possible but unlikely that the pantry light has a permanent (i.e., always live) line. More likely it just gets a switched line from either the light fitting or the switch in the corridor.

Best bet is to open up the corridor switch and light fitting and the pantry light fitting and have a look. My guess would be that the pantry light fitting has just one twin-and-earth cable arriving at it, in which case there'll only be switched line available there. Obvious precautions, first, of course.

(BTW, the three wires in a typical domestic power cable are line, neutral and earth. Line and neutral are both considered to be live wires. The colloquial use of “live” for the L (brown) wire is, at best, out dated - I'm not sure of the history.)
- CommentAuthorWillInAberdeen
- CommentTimeDec 26th 2020 edited
Put the corridor light also on a smart bulb. Leave the mains switch permanently on, to power both. Control each of the corridor and pantry with separate smart switches, PIRs, light sensors, whatevers. Why not put a PIR on the corridor as well as a smart switch, so it goes off when not needed?

I had the same problem as Rex and had a thread recently about it, this was the suggested solution and has worked a treat. I think the kit was about a tenner. (Edit - £21 for three lights: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16243 )

Some people even link out and remove the mains switch and stick a smart switch in its place, I didn't.
- CommentAuthorPeter_in_Hungary
- CommentTimeDec 26th 2020
Posted By: Rexbut how do I check if the pantry light has an active live?

Easiest way is to use a mains detector screwdriver - the ones with a neon in the handle.

Properly done the live should be switched and the neutral would be permanent - but this can't be guaranteed, it depends who did the wiring.

Posted By: RexThe corridor light would be switched, the pantry always activated by the PIR; assume that means the pantry PIR has to have a permanent live mains

correct - actually you need a permanent live and permanent natural to the PIR.
- CommentAuthorPeter_in_Hungary
- CommentTimeDec 26th 2020
Posted By: WillInAberdeenPut the corridor light also on a smart bulb. Leave the mains switch permanently on, to power both. Control each of the corridor and pantry with separate switches, PIRs, light sensors, whatevers. Why not put a PIR on the corridor as well as a switch, so it goes off when not needed?

cross posted with Will
PIRs on both lights and both left switched on sounds like a good fix !
- CommentAuthorEd Davies
- CommentTimeDec 26th 2020
Posted By: Peter_in_HungaryPIRs on both lights and both left switched on sounds like a good fix !
Sounds a weird approach to me if it's only necessary to move one wire to get what's actually wanted (plus adding the PIR sensor in the pantry, of course), as it would be in two out of the three most likely ways the existing wiring is arranged.
- CommentAuthordjh
- CommentTimeDec 27th 2020
Posted By: Ed Davies
Posted By: Peter_in_HungaryPIRs on both lights and both left switched on sounds like a good fix !
Sounds a weird approach to me if it's only necessary to move one wire to get what's actually wanted (plus adding the PIR sensor in the pantry, of course), as it would be in two out of the three most likely ways the existing wiring is arranged.

I agree with Will and Peter. Moving/adding one wire is an order of magnitude more difficult than adding PIRs (assuming the wires are behind the ceiling and not in conduits).

There's no need for separate PIRs either. Rex could just replace the luminaires with ones that have a built-in PIR or microwave sensor.
- CommentAuthorEd Davies
- CommentTimeDec 27th 2020
Posted By: djhMoving/adding one wire is an order of magnitude more difficult than adding PIRs
Really? Undo two screws, move wire end, do up two screws? I.e., move the line to the pantry light from switched line to permanent line either on the corridor light fitting (most likely) or the light switch (quite possible).

Saves having a PIR on the corridor light fitting which is not necessary and maybe not even wanted - I know I'd find a light which keeps coming on when it's not really needed quite annoying.
- CommentAuthorWillInAberdeen
- CommentTimeDec 27th 2020 edited
I suggested to have a wireless PIR in the corridor **as well as a wireless smart switch** so you can turn it on the old way if you want, or it will turn itself on for you and off when you've gone. But no need to have a PIR on the corridor if not wanted - if preferred, just use a wireless lightswitch (I did that) which can be stuck to the wall wherever is convenient. Or several wireless switches, each end of the corridor? Mine were £6.

Worth a read of the thread I linked to - I investigated those three wiring possibilities that Ed mentioned, and found it was actually a fourth configuration with the loop through an inaccessible junction box instead of through the switch or any of the light fittings. But wireless lightswitching makes these wiring limitations all irrelevant, you can now switch any light from anywhere you like, and change it when you fancy, and Rex doesn't have to go near any live terminals to do it!

Or even simpler, unscrew the light bulb from the pantry fitting, and screw in a new lightbulb with a built-in PIR in the bulb - £5 on eBay.

BTW the voltage detector 'pens' are much easier and safer than a neon screwdriver, for finding whether a fitting has a permanent live, no need to open the fitting.

One for the sparkies: is it legal to have a permanent unswitched live feeding a PIR light fitting, or are you required to have a hard wired switch to turn it off when you change the bulb?
- CommentAuthorRex
- CommentTimeDec 27th 2020
As usual, thanks for all the thoughts; much appreciated. Don't fancy a PIR in the corridor as it would be activated every time we go to the utility or back door.

As an easy pantry light, I have for some time had a battery, PIR operated Lidl special to provide light without having to turn the main light on. It does what it says on the box but does not really illuminate the space.

And now, to illustrate my total Luddite-ness, what is a SmartSwitch? I was under the impression all these 'smart' items operated from the phone, voice, or whatever.
- CommentAuthorEd Davies
- CommentTimeDec 27th 2020
Posted By: WillInAberdeen: “One for the sparkies: is it legal to have a permanent unswitched live feeding a PIR light fitting, or are you required to have a hard wired switch to turn it off when you change the bulb?”

Good question. Even if it's legal it might not be sensible. How about using a PIR sensor with a built in switch? Something like this:

https://www.amazon.co.uk/gp/product/B07ZTGRQ3G/ref=ox_sc_act_title_1?smid=A15TW43BF9Y9WW&psc=1
- CommentAuthorPeter_in_Hungary
- CommentTimeDec 27th 2020
Posted By: RexAt the time, one light was ceiling mounted to illuminate the corridor and pantry. Then we decided to fit doors to the pantry, and I added and extension light so the one switch turns on both lights (corridor and pantry.)

To me this implies that the pantry light was extended from the ceiling light which would make getting a permanent live to the pantry difficult. How the pantry light was put in is key to the solution.

Posted By: RexDon't fancy a PIR in the corridor as it would be activated every time we go to the utility or back door.

But only when the light level was low - when you would probably switch the light on anyway.
- CommentAuthorborpin
- CommentTimeDec 28th 2020
Posted By: RexWhat would be nice is for the switch to continue to activate the corridor light, but have the pantry light on a PIR switch, only activated when one enters the pantry.
I used one of the Ikea wardrobe door light strips on our cloakroom. Works really well and so easy to fit.
- CommentAuthorWillInAberdeen
- CommentTimeDec 28th 2020
Posted by Rex:"And now, to illustrate my total Luddite-ness, what is a SmartSwitch? I was under the impression all these 'smart' items operated from the phone, voice, or whatever."

Me too! But no. Try here:
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16243
- CommentAuthorEd Davies
- CommentTimeDec 28th 2020
Posted By: Peter_in_HungaryTo me this implies that the pantry light was extended from the ceiling light which would make getting a permanent live to the pantry difficult.
s/would/could/

It could be trivial depending on how the existing wiring is laid out. This conversation is getting tediously repetitive.
- CommentAuthorphiledge
- CommentTimeDec 28th 2020
Posted By: WillInAberdeen

One for the sparkies: is it legal to have a permanent unswitched live feeding a PIR light fitting, or are you required to have a hard wired switch to turn it off when you change the bulb?

Given that a room light switch is not considered to be a safe means of isolation, I doubt any authority would legally require a switch to be provided for isolation. Id be fairly sure anyone changing a bulb would officially be guided to knock the power off at a lockable mcb/mainswitch, although I guess most of us rely on the light switch for bulb changing!!
- CommentAuthordjh
- CommentTimeDec 28th 2020
Posted By: philedgeGiven that a room light switch is not considered to be a safe means of isolation, I doubt any authority would legally require a switch to be provided for isolation. Id be fairly sure anyone changing a bulb would officially be guided to knock the power off at a lockable mcb/mainswitch, although I guess most of us rely on the light switch for bulb changing!!

It'll all be alright unitl some MPs daughter is electrocuted and then we'll need isolators on every light switch and all lighting to be SELV or PELV
- CommentAuthorWillInAberdeen
- CommentTimeDec 28th 2020 edited
That's perhaps why we have RCDs on lighting circuits now? That, and picture hook nails.

Always found it odd that the metal contacts in the bottom of a light socket, are the only live parts of a household installation that are routinely exposed, such that a householder can physically touch live with their finger. Everything else is shrouded in layers of plastic, so the MP's offspring would need a screwdriver if he/she wants to electrocute him/herself.

Per DJH's suggestion, house wiring might become cheaper if there was just a 12V permanent live, running round to every fitting, no wiring runs down walls to lightswitches, all switching done wirelessly.... watch this space!
- CommentAuthordjh
- CommentTimeDec 29th 2020
Posted By: WillInAberdeenno wiring runs down walls to lightswitches, all switching done wirelessly

Yes, I've been wondering how long it takes until that becomes normal. When the mainstream manufacturers start making (or branding) wireless switches and wireless receivers cheaper than conventional parts it'll be an overnight change but until then it's a question of how much of a spark's time is saved, I suppose. (I don't buy in to the concept of smart bulbs, I'm afraid - dumb bulbs for me and separate switching)
- CommentAuthordereke
- CommentTimeDec 29th 2020 edited
Posted By: WillInAberdeenPer DJH's suggestion, house wiring might become cheaper if there was just a 12V permanent live, running round to every fitting, no wiring runs down walls to lightswitches, all switching done wirelessly.... watch this space!

Yesterday I discovered that lighting powered by PoE (power over ethernet) is a thing. 24/48v and every fixture is a smart light. The only problem with this is it all goes back to a PoE switch and they can be quite expensive if you have a lot of fixtures. I like the idea though.
- CommentAuthorEd Davies
- CommentTimeDec 29th 2020
Posted By: WillInAberdeenhouse wiring might become cheaper if there was just a 12V permanent live
48V? Highest “round” voltage which is considered safe from the shock point of view whilst minimising current. PoE compatible. Allows buck conversion for the full range of USB-C power voltages (up to 20V) whereas 12V would need buck/boost converters. Not uncommon off-grid voltage.

Or maybe 36V (or whatever it is, 32V?) if this idea of re-standardising car electric voltages comes to anything. Not sure what's happening in that space.

Wireless switching is worth it just to be able to put a conventional-looking light switch in the bathroom zones to freak people out.
- CommentAuthorWillInAberdeen
- CommentTimeDec 29th 2020 edited
The kinetic wireless switches and relays I bought (on DJH's recommendation and others') were £21 for 3 lights, which I think would be comparable with cost of 240V switches, back boxes, cable and conduit. As you say, the saving would be avoidance of time spent fitting and testing fixed wiring, plus maybe avoidance of holes in plasterboard.

I too started out by looking to put the smart bits in the permanent wiring, and so have dumb lightbulbs, but am now rethinking because:

1) the technology moves quickly eg incandescent>halogen>CFL>LED>Smart has happened in bit over a decade. The permanent wiring shouldn't need changing that often.

2) there are too many 'smart' systems at the moment, most are proprietary and the rest are heath-robinson, a common interoperable standard hasn't emerged yet. To build one system into the permanent wiring means backing one horse out of many.

3) we have a set of RGB colour changing LED and despite my scepticism it is actually quite nice to have cool white work light during the daytime and warm white light in the evening. Couldn't do that with dumb bulb.

4) smart bulbs offer features such as built-in motion detectors, or adjust their lighting level depending on daylight level. Couldn't do that as easily with permanent wiring, as Rex found.

5) prices of smart bulbs are falling faster than of smart relays AFAICS.

I am also wondering about the self adhesive LED tape which is brilliant stuff (hoho). The 'normal' approach of running permanent wiring to a 240V fitting in the middle of each ceiling, could be replaced by led tape lighting running round the cornices (or skirting boards, window frames, tabletops, wherever). That would disrupt the design of permanent wiring, like recessed downlighting has.
- CommentAuthorWillInAberdeen
- CommentTimeDec 29th 2020 edited
Posted By: Ed Davies48V? 20V 12V 36V 32V

So many possibilities! The ideal might be to have the most efficient 240V to ELV conversion done in one place, then avoid each bulb needing to include it's own voltage converter which takes space and gets hot. The required forward voltage for the LED might be 2V and for the smart logic might be 3-5V ? If the house permanent wiring were at say 5V then maybe the LED and the smart logic could all go on a single chip with minimal other components, how cheap could that be?

Edit: the voltage and energy loss in the wiring might be significant though..

Another edit:
Posted By: Ed Davies48V? Highest “round” voltage which is considered safe from the shock point of view
I understand that SELV is defined as less than 50V RMS AC, or less than 120V DC. However that is not considered safe for people to touch and so all the usual basic protections still apply, eg the cables must be sheathed as well as insulated, run in protected ways, insulation resistance tested and certified after installation by a recognised competent person etcccc. This applies to all SELV supplies, apparently/technically including PoE (!)

There are references to supplies below 12V RMS AC or 30V DC PELV having reduced requirements but Im far from expert.
- CommentAuthordereke
- CommentTimeDec 29th 2020
Posted By: WillInAberdeen1) the technology moves quickly eg incandescent>halogen>CFL>LED>Smart has happened in bit over a decade. The permanent wiring shouldn't need changing that often.

The advantage with PoE is that it won't go away anytime soon as it is used extensively in other industries.

Posted By: WillInAberdeenThe kinetic wireless switches and relays I bought (on DJH's recommendation and others') were £21 for 3 lights,

Hmm I bought some of these, it was that price for a 3way switch and then £20 per receiver. Not cheap but useful in certain circumstances. Which ones did you get? I got Quinetic from tlc-direct.
- CommentAuthorWillInAberdeen
- CommentTimeDec 29th 2020 edited
I bought from eBay, £6 for 3gang switch and £5 per relay, see thread I linked above. Sold as unbranded, but actually arrived with brand stickers on it.

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General: Adding a PIR switch