LED dimming question

[dsharp7th]

I had success selecting and specifying LED lighting for my extension - a mixture of dimmable integrated downlights and LED tape. Despite not being an electrician, I managed to teach the installing sparky a thing or two from my hours of research. Especially the intricacies of configuring Varilight V-Pro dimmers.

I'm pleased with all the results, but for one thing, the two downlights in the little understairs WC are too bright. It would be easy enough to swap the existing 1way switch for a dimmer, but I would prefer to have a 1way switch to turn the lights on to a pre-set dimness (because kids and easily confused old people etc.).

My question - would it be acceptable to add a suitable dimmer (probably this one https://www.tlc-direct.co.uk/Products/LTJP400MOD.html ) in series with the 1way switch, set it to the required level, hide it within the stud wall (but accessible by removing the dry lining box), then use the 1way switch to control the lights at the right level? It would seem similar to the way LV transformers are 'lost' in ceilings and stud walls, but I can just imagine falling foul of a reg that says no.

Any thoughts?

(there is the additional complication of the dimmer upsetting the extractor fan, but looking at other posts on here, I wont find out if that's a problem until I try it)

 

[Lectrician]

Put the dimmer vertically above the switch, high up out the way. It is not compliant to loose it in the wall.

 

[winston1]

Why not change the downlights for lower power ones or even just have one?

 

[dsharp7th]

Ok, thanks Lectrician, suspected this might be the case. Is it that any controller has to be accessible, or is it just to avoid hiding things that future buyers wouldn't know about?

A single downlight is bad for shadows, and was hoping to use a <£10 dimmer rather than >£40 of new downlights.

Or maybe I need to consider alternatives to white emulsion for the smallest room in the house...

 

[Lectrician]

Terminations, other than crimped or soldered (or etc), need to be accessible. In a wall, behind a dry liner or otherwise, is not accessible.

 

[ban-all-sheds]

A single downlight is bad for shadows.

That's because they are not meant to be used for lighting up rooms. You have chosen lighting not fit for purpose.

 

[ericmark]

The product you have selected is designed for "LEDlite" which it seems is a 10W unit with a very low efficiency of 54 lumen per watt. It does not show how wired, but likely it does not require a neutral which means it has to get the power to work through the lamp it controls. Likely the poor efficiency of the lamp is due to using the first 3 mA or so to work the dimmer switch and the switch controls the remaining 40 mA or so to get zero to full light.

Use the dimmer with another product and it may not work as expected. A dimmer switch with LED lighting has to talk to the lamp and tell the lamp what is expected. The normal LED lamp has a driver built in which will regulate the current to the LED this means an LED lamp will often give same output from 150 volt to 250 volt so the dimming switch has to not simply reduce power as with a tungsten lamp but send some signal to the driver in the LED lamp to tell it to reduce output. Often the driver reads the chopped wave form to gain this information.

So LED lamp and dimmer must be matched. This is where the problems start, used with a replaceable bulb there is no way to ensure they match. The "LEDlite" is a complete unit the bulb and fitting are one you can't replace the bulb so can't mess it all up using wrong bulb.

The idea of fitting multi-bulb fittings or loads of fittings and switching in more or less light works very well, in Europe where they have used CFL well before us in the main to keep rooms cool they have for years split their lights into 1/3 and 2/3 giving three levels of lighting. However changing existing to that method is not very easy as clearly needs the extra wires.

One way around the problem is to have some lighting using a PIR or pull switch and some on the original wall switch which saves having to modify wiring to the wall switch. But that seems rather over kill for a WC as does having a very low wattage lamp on 24/7. It seems like cracking a nut with a sledge hammer and it would seem best option is simply replace the lights for a smaller version. However I personally don't read my paper while sitting on the WC, but I know many do. Fitting a reading lamp in the WC room just seems odd to me, but judging from the number of people I have worked with who have to get a paper to read before going to toilet it is clearly common.

A lot depends on the down lighters used. The down lighter in my house is a 22W 2D unit which would light a WC great for reading in, but not sure if a 2" down lighter would give the spread required. So first question has to be are the down lighters used compatible with the dimmer selected? Second if dimmer is to be hidden does it have maintenance free connections? And third if hidden will it get enough cooling?

 

[seasickstevie]

Not sure if I can picture what a 22w 2D downlighter looks like

 

[dsharp7th]

ok thanks folks. Lectrician answered my question. For the record one downlight is over the sink and one, yes, for reading on the loo.

For reference that dimmer I linked to is the bare bones dimming module of the Varilight V-Pro range. TLC are describing it with reference to their own brand of LED downlights (which I tried and rejected in favour of something better), but V-Pro dimmers work fine with everything I have used them with - LED and halogen downlights, LED tape with dimmable transformers, retrofit LED B22s, and old school incandescent, and they're surprisingly configurable for a push switch/rotary knob. So I was confident in the scenario I described working, just needed a steer on the regs.