Dimmer switch works to turn on/off but no dimming

[trionic]

BG triple dimmer switch. First dimmer controls five lamps via three cables (two of the lamps are daisy-chained to another). Second dimmer controls three lamps, all daisy-chained). Third dimmer's wired but with nothing on the end yet.

Started with this:

Ended with this:

So. Into L2 of dimmer 1 is the supply (from a downrated 3A FSU off the ring main). There is a link wire from L2 of dimmer 1 to L2 of dimmer 2 and then to L2 of dimmer 3.

Into switched live of dimmer 1 are three live conductors for three supplies to five lamps.

Into switched live of dimmer 2 is one live conductor for a supply to three lamps, all daisy-chained.

Into switched live of dimmer 3 is a flex which is for a lamp which is not yet connected (end of flex is capped-off).

All the earths are terminated at the faceplate.

All neutrals are connected together on a Wago block; two conductors per port.

Dimmer 1 works fine to control the five lamps on that circuit.

Dimmer 2 switched the three lamps on and off fine but the dimmer control does nothing. The lamps remain ar what appears to be full output.

Dimmer 3 does nothing 'cos it's not connected to a lamp.

Now, I am not especially happy with the wiring because it looks to be too busy and there are probably too many conductors per dimmer or Wago port so I am open to suggestions for tidying that up. This is DIY work which will be tested by a qualified electrician and a Small Works certificate provided so I want the end result to be compliant.

But first I want to fix the problem with dimmer 2 not dimming. Have I made a wiring error?

Thanks for reading a long post and thanks for your advice.

 

[flameport]

But first I want to fix the problem with dimmer 2 not dimming.

Most likely is the dimmer is bust, which usually happens when a tungsten lamp fails. Less likely is it's connected to LED lamps which are not dimmable.

For the rest - the cables are stripped far too short, and enclosures must be made from non-combustible materials, so having a big piece cut out and exposed timber is not permitted.

 

[333rocky333]

If the lights switch on/off then seems like a faulty dimmer. did you by any chance accidentally short it out , its quite common that once blown the Triac fails.
You could move the output over to the unused dimmer, but you could risk blowing that one.
Whats the 2 core flex for, should really be 3 core

 

[markyd1]

big hole in back box a no no....6 cables in a 3 way wago a no no...2 core flex a no no,,getting a sparky to test and certify unless he is 3rd party registered a no no

 

[muffking]

But first I want to fix the problem with dimmer 2 not dimming. Have I made a wiring error?

Your wiring order seems fine other than the Live feeds should be linked through the Commons and your switched lives out of L1.
Swap dimmer 2 & 3 over to check the dimming for the 3 light run, that way you can replace the faulty dimmer at your leisure.

Now, I am not especially happy with the wiring because it looks to be too busy and there are probably too many conductors per dimmer or Wago port so I am open to suggestions for tidying that up. This is DIY work which will be tested by a qualified electrician and a Small Works certificate provided so I want the end result to be compliant.

Aside from what has been picked up, get yourself an 8-way Wago (lever type 222-418) to tidy up the neutrals. They won't be properly secure stuffed in a smaller Wago. It has to remain a lever type by the way as the flex won't push in to a push fit Wago.

Re the flex, it really should have an earth. Is it too late to run one or better still replace the cable with T&E?
Without an earth you can't use any Class 1 metal lights or fittings.

FWIW you could do the Minor Works Cert yourself as you'll struggle to get an electrician to put their name to someone else's work. Even the use of a Class 2 non earthed light on dimmer 3 as it stands would be an issue as we just wouldn't have used that cable.
By all means get it checked over for safety though.

 

[trionic]

Thank you for all of the replies.

A local electrician agreed to test and inspect prior to me doing any of this work. After the wiring had been installed into the stud paritions and clipped to walls, he inspected the work so far and gave his approval and agreed to return to test when the work was finished.

I will connect dimmer 2's wiring to dimmer 3 to test. Dimmer 2 was not shorted-out.

The LED lamps on dimmer 2 are all dimmable.

the cables are stripped far too short, and enclosures must be made from non-combustible materials, so having a big piece cut out and exposed timber is not permitted.

I didn't know about the strip length on the cables. What is the rule?

The plasterboard cut-out was originally for a 2-gang dimmer in a 1-gang back box but was expanded to a 3-gang in a 2-gang box, and a section of plasterboard was cut out, hence the appearance of the stud. The timber's not load bearing and is screwed to brickwork along its height, so I could chop-out a section of the wood so that a new and un-hacked back box can be installed. Would that be acceptable?

Your wiring order seems fine other than the Live feeds should be linked through the Commons and your switched lives out of L1.

Now I'm confused. The BG data sheet (PDF) for the 3-gang dimmer lists L2 as the live supply and common as the switched live. That's why the link is across the three L2s.

For 1-way switching I had expected to use common as live supply and L1 as switched live but the BG wiring seemed to suggest different. I think I misinterpreted the diagram and what is meant by "switched live".

get yourself an 8-way Wago (lever type 222-418) to tidy up the neutrals. They won't be properly secure stuffed in a smaller Wago.

I can only find knock-off 8-way connectors and Wago don't list the 222-418 on their web site. Why an 8-way when there are 6 neutrals?

Should the neutrals have a brown sleeve?

Whats the 2 core flex for, should really be 3 core

Re the flex, it really should have an earth. Is it too late to run one or better still replace the cable with T&E? Without an earth you can't use any Class 1 metal lights or fittings.

The flex was run at a late stage and I had limited options and the flex had to be hooked through the wall, and was for a non-earthed non-metal light fitting. TBH I may abandon that third circuit.

Again, thanks for the advice. Perhaps this installation can be rescued

 

[muffking]

A local electrician agreed to test and inspect prior to me doing any of this work. After the wiring had been installed into the stud paritions and clipped to walls, he inspected the work so far and gave his approval and agreed to return to test when the work was finished.

Yep that's fine. He can't do an MWC as he wasn't the installer, but he can do a condition report.

so I could chop-out a section of the wood so that a new and un-hacked back box can be installed. Would that be acceptable?

Yes. If it's not structural then just chop a section out. Best tool to use is a reciprocating multi-tool if you have one.

Now I'm confused. The BG data sheet (PDF) for the 3-gang dimmer lists L2 as the live supply and common as the switched live. That's why the link is across the three L2s.

For 1-way switching I had expected to use common as live supply and L1 as switched live but the BG wiring seemed to suggest different. I think I misinterpreted the diagram and what is meant by "switched live".

I had a quick scan through the instructions and it shows both ways. There's no issue with the way you did it for 1-Way, just if you stick to Live for Common then there's no confusion when wiring up 2-Way. This doesn't apply to you, so I wouldn't worry.

I can only find knock-off 8-way connectors and Wago don't list the 222-418 on their web site.

They probably were knock offs then despite using Wagos part number.
May need to link a couple of 4 or 5 ways then, or use a large terminal block if there's room.

Should the neutrals have a brown sleeve?

No. All of your blue's are Neutral and all of your brown's are either Live or Switched Live.


The flex was run at a late stage and I had limited options and the flex had to be hooked through the wall, and was for a non-earthed non-metal light fitting. TBH I may abandon that third circuit.

Again, thanks for the advice. Perhaps this installation can be rescued [/QUOTE]

 

[trionic]

Yep that's fine. He can't do an MWC as he wasn't the installer, but he can do a condition report.

My mistake on the terminology then. As long as I have something which states the work is compliant then I'll be satisfied.

Yes. If it's not structural then just chop a section out. Best tool to use is a reciprocating multi-tool if you have one.

Got one of those Should be easy to cut out a small section.

They probably were knock offs then despite using Wagos part number. May need to link a couple of 4 or 5 ways then, or use a large terminal block if there's room.

Originally I used a screw-type terminal block but replaced it with the Wago. Can't believe I'm watching videos on spliced wiring connectors, but the knock-off look to be good in terms of construction and function (caution: 150 amp connector torture). Of course, that applies only to those particular knock-offs and not those from other factories.

For £12 I can get a bag of ten, take one apart, inspect it and if it looks okay then I'll use that.

Thanks

 

[oldbutnotdead]

Your LEDs may well be marked as dimmable but LEDs dim in a different way to tungsten- with tungsten you dim by varying voltage, with LED you dim by varying current. Assuming those are standard cheapie triac dimmers then I'm surprised the LEDs work at all never mind not dimming.

 

[trionic]

Your LEDs may well be marked as dimmable but LEDs dim in a different way to tungsten- with tungsten you dim by varying voltage, with LED you dim by varying current. Assuming those are standard cheapie triac dimmers then I'm surprised the LEDs work at all never mind not dimming.

I should have mentioned that I tried a tungsten lamp in one of the three fittings, but the result was the same. That may not be a valid test, so I will try tungsten lamps in all three fittings, just to be sure.

The BG dimmer is of the leading-edge type and the datasheet says that it's compatible with all LED lamps. Whether that's true or not I do not know.

 

[oldbutnotdead]

I should have mentioned that I tried a tungsten lamp in one of the three fittings, but the result was the same. That may not be a valid test, so I will try tungsten lamps in all three fittings, just to be sure.

The BG dimmer is of the leading-edge type and the datasheet says that it's compatible with all LED lamps. Whether that's true or not I do not know.

OK, does the datasheet give you minimum loads? (If the load is too low then the triac won't switch off properly). EDIT looks like they want at least 60w of load to function properly, on the back of the dimmer it says 60-400VA- that's a lot in these days of LEDs (nowt in terms of tungsten). Stick a decent load on the end of it & see if it works

 

[trionic]

Stick a decent load on the end of it & see if it works

Good idea. I tested it with 3x 42w halogen lamps but with the same result.

The lamp fittings are E27 and 42w is the highest power lamp I have but 126w should have been enough.

 

[oldbutnotdead]

Good idea. I tested it with 3x 42w halogen lamps but with the same result.

The lamp fittings are E27 and 42w is the highest power lamp I have but 126w should have been enough.

Well that should have been enough. Have you tried with the 3rd dimmer yet?

 

[flameport]

I didn't know about the strip length on the cables. What is the rule?

There is no rule, but generally the cables should be stripped long enough so that the Wago or whatever other terminals are used can stay in the back of the box, and there is enough length so the switch can be wired up, and the wires then folded in behind it as it's fitted into the wall.
The grey outer coverings should not be moving within the wall as the switch is fixed to the box.

If the wooden piece is to be cut out, dispose of that plastic box and get a 47mm metal one instead. It can be screwed to the timber to secure it.

For £12 I can get a bag of ten,

The genuine items are half that price. https://www.toolstation.com/search?q=wago
and TS deliver for free if you spend at least £10.
There is no 8 lever version, the correct thing is the 8 way pushwire https://www.toolstation.com/wago-2273-8-way-compact-pushwire-connectors/p35132
which takes up far less space, and that's also why using T&E is essential as flex won't fit into those.

It won't make any difference which way round L and SL are connected to the dimmer. Those ones are wired with one wire to the ~ terminal, and the other wire to either L1 or L2.
If you connect the two wires to L1 and L2 it just won't work at all, nothing will be damaged.

 

[333rocky333]

Your wiring order seems fine other than the Live feeds should be linked through the Commons and your switched lives out of L1.
.

Whys that?

Not that it matters on AC, but there is no COMMON terminal, he has connected the outputs to the Terminals marked with a squiggly line and an Arrow through it, which is the symbol for a Variable Output.
As for Supply into L1 or L2 it wont matter, as if a Push On/Off switch was ever used as 2 way, its likely to be fed from either of the 2 way Strappers