Smart switch no neutral issue

[Jethro_uk]

Have a fluorescent fitting which I retrofitted an LED tube to. All worked
fine.

Upgraded to a smart switch. The wiring in the box is just 2 wires - live
and load. All worked fine with live to "L" and load to "L1".

Smart switch failed after 6 months - the little LED comes on and goes off
when you press and hold the switch, but nada.

Sourced a replacement while waiting for the exchange. Slightly different
look but same connections. However this didn't work.

I wired it into a L+N test rig and it works fine.

Back to the light - I connected a capacitor that was supplied with a
different smart switch across the incoming live and neutral in the light
fitting. Still no joy.

The switch instructions show a non-neutral setup with a capacitor across
the load. So this isn't unsupported. Moreover I had a switch which *did*
work.

Clearly I am missing a trick here. Does this make sense to anyone else ?

[Theo]

Post by Jethro_uk
Have a fluorescent fitting which I retrofitted an LED tube to. All worked
fine.
Upgraded to a smart switch. The wiring in the box is just 2 wires - live
and load. All worked fine with live to "L" and load to "L1".
Smart switch failed after 6 months - the little LED comes on and goes off
when you press and hold the switch, but nada.
Sourced a replacement while waiting for the exchange. Slightly different
look but same connections. However this didn't work.
I wired it into a L+N test rig and it works fine.
Back to the light - I connected a capacitor that was supplied with a
different smart switch across the incoming live and neutral in the light
fitting. Still no joy.
The switch instructions show a non-neutral setup with a capacitor across
the load. So this isn't unsupported. Moreover I had a switch which *did*
work.
Clearly I am missing a trick here. Does this make sense to anyone else ?

Some no-neutral smart switches acquire power by trickling current through
the load, which gives them enough voltage drop to scavenge power. That only
works with a filament bulb because you can't trickle through a fluoro or
some forms of LED PSU. Have you changed the LED recently?

Otherwise I think they try to harvest power when the light is on, when
there's enough current flowing to cause a voltage drop, and store that in a
supercap. That only works if the light is on regularly enough to charge the
supercap.

I suppose putting a cap in series with the load might act as a capacitive
dropper and also offer some voltage drop.

The one variable here is the LED driver, which is something the switch
doesn't know anything about. All this trickling and dropping only works if
the load will allow current to flow. Maybe your switch and tube combination
are incompatible? Maybe there's something about fluoro-replacements that
make them look different from bulbs?

Unfortunately no-neutral switches are a hack at best, so it might be trial
and error to find something that works. A filament should, but I don't know
about fluoros or fluoro-replacements.

Or get one with a battery that doesn't need to scavenge power?

Theo

[Jethro_uk]

Post by Theo

Post by Jethro_uk
Have a fluorescent fitting which I retrofitted an LED tube to. All
worked fine.
Upgraded to a smart switch. The wiring in the box is just 2 wires -
live and load. All worked fine with live to "L" and load to "L1".
Smart switch failed after 6 months - the little LED comes on and goes
off when you press and hold the switch, but nada.
Sourced a replacement while waiting for the exchange. Slightly
different look but same connections. However this didn't work.
I wired it into a L+N test rig and it works fine.
Back to the light - I connected a capacitor that was supplied with a
different smart switch across the incoming live and neutral in the
light fitting. Still no joy.
The switch instructions show a non-neutral setup with a capacitor
across the load. So this isn't unsupported. Moreover I had a switch
which *did* work.
Clearly I am missing a trick here. Does this make sense to anyone else ?

Some no-neutral smart switches acquire power by trickling current
through the load, which gives them enough voltage drop to scavenge
power. That only works with a filament bulb because you can't trickle
through a fluoro or some forms of LED PSU. Have you changed the LED
recently?
Otherwise I think they try to harvest power when the light is on, when
there's enough current flowing to cause a voltage drop, and store that
in a supercap. That only works if the light is on regularly enough to
charge the supercap.
I suppose putting a cap in series with the load might act as a
capacitive dropper and also offer some voltage drop.
The one variable here is the LED driver, which is something the switch
doesn't know anything about. All this trickling and dropping only works
if the load will allow current to flow. Maybe your switch and tube
combination are incompatible? Maybe there's something about
fluoro-replacements that make them look different from bulbs?
Unfortunately no-neutral switches are a hack at best, so it might be
trial and error to find something that works. A filament should, but I
don't know about fluoros or fluoro-replacements.
Or get one with a battery that doesn't need to scavenge power?

Thanks for that. It's a little frustrating as until it decided to not
work, the one I had in place worked fine for 6 months. Hopefully I will
get an identical one from the vendor in the new year.

I'm not too bent out of shape as the one I'm trying now was less than £8
from China in 6 days.

I agree the LED drop-in replacement for the fluorescent tube is the
unknown quantity here. All my other smart switches work fine with no
neutral and "regular" LED lamps.

[David Wade]

Post by Jethro_uk
Have a fluorescent fitting which I retrofitted an LED tube to. All worked
fine.
Upgraded to a smart switch. The wiring in the box is just 2 wires - live
and load. All worked fine with live to "L" and load to "L1".
Smart switch failed after 6 months - the little LED comes on and goes off
when you press and hold the switch, but nada.
Sourced a replacement while waiting for the exchange. Slightly different
look but same connections. However this didn't work.
I wired it into a L+N test rig and it works fine.
Back to the light - I connected a capacitor that was supplied with a
different smart switch across the incoming live and neutral in the light
fitting. Still no joy.
The switch instructions show a non-neutral setup with a capacitor across
the load. So this isn't unsupported. Moreover I had a switch which *did*
work.
Clearly I am missing a trick here. Does this make sense to anyone else ?

Is the the sort of switch where you push it and the light switches on
for a set period of time?

I tried several versions for my downstairs loo with and without a
capacitor, but none lasted more than a few months...

.. in desperation I tried an old fashioned pneumatic plunger but that
didn't stay on long enough for me to finish the crossword, so in the end
I wired the switch permanently on and fitted an infra-red sensor from
screwfix.

It can be set accurately and a quick wave will re-start the time should
I be struggling with the crossword. Its been there for nearly two years
now and still works fine...

Dave

[Tricky Dicky]

Post by David Wade

Post by Jethro_uk
Have a fluorescent fitting which I retrofitted an LED tube to. All worked
fine.
Upgraded to a smart switch. The wiring in the box is just 2 wires - live
and load. All worked fine with live to "L" and load to "L1".
Smart switch failed after 6 months - the little LED comes on and goes off
when you press and hold the switch, but nada.
Sourced a replacement while waiting for the exchange. Slightly different
look but same connections. However this didn't work.
I wired it into a L+N test rig and it works fine.
Back to the light - I connected a capacitor that was supplied with a
different smart switch across the incoming live and neutral in the light
fitting. Still no joy.
The switch instructions show a non-neutral setup with a capacitor across
the load. So this isn't unsupported. Moreover I had a switch which *did*
work.
Clearly I am missing a trick here. Does this make sense to anyone else ?

Is the the sort of switch where you push it and the light switches on
for a set period of time?
I tried several versions for my downstairs loo with and without a
capacitor, but none lasted more than a few months...
.. in desperation I tried an old fashioned pneumatic plunger but that
didn't stay on long enough for me to finish the crossword, so in the end
I wired the switch permanently on and fitted an infra-red sensor from
screwfix.
It can be set accurately and a quick wave will re-start the time should
I be struggling with the crossword. Its been there for nearly two years
now and still works fine...
Dave

When I re-wired our bungalow I did consider looping in at the switches thus
providing a neutral but owing to the fact that the roof pitch is so shallow
you cannot stand up in our loft and possibly working in the extremes of
the trusses, I opted for running a series of Wago boxes down the spine of
the house branching off to the switches and rosettes. The plan being to use
Quinetic switches where I want smart functionality by simply removing the
switch wire and wiring in a Quinetic WiFi receiver at each Wago box where I
need smart functionality and replacing the switch plate with a Quinetic
switch this would enable switching either with the switch or Alexa voice
control.

Richard