Wemo dimmer switch on NZ/AU grid - Page 1
Forum section: electronics / general

author: nzmikec
author_rank: Contributor
timestamp: May 29, 2020, 01:04:32 am
content: Hi All,My first post so please any feedback is most appreciated.Ive been using Wemo dimmershttps://www.belkin.com/us/p/P-F7C059/purchased from USA in NZ for around a year with only one issue. The issue I get is occasionally and sometimes on schedule (time of day) I get a strobing effect of the connected LED's. Now I know these devices are not certified to work on our 240v 50hz grid. These have however not overheated or failed despite using them for around a year in our home. I have several of these switches and they all strobe at the same time. Some of them area also on different MCB'sI have disassembled a switch (that incidentally has a partially failed fuse) to ensure using the unit on 240v is safe. All of the power components I have found a data sheet on are well within spec at 240v. See attached photos.I was hoping for a bit of a technical insight to this strobing issue im having. I know there is some interference on our grid that seems to coincide with the timing of the strobing of the dimmers, I've seen a standard incandescent bulb (no dimmer) slightly pulsating at the same time. I dont have the equipment to scope the grid waveform unfortunately. I know our local power grid has a ripple control system for controlling fixed loads on a slightly reduced rate.Im thinking that maybe the ripple control signal or the noise on the grid might be causing the switches to go out of sync from the grid. They are using leading edge dimming. Might this be because they are designed for a 60ghz grid? If so I wonder if there is a component that might be swapped to make them compatible with 50hz?Any insight or experience would be greatly appreciated!Regards,Mike

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 29, 2020, 04:59:49 am
content: Quote from: nzmikec on May 29, 2020, 01:04:32 amHere's some feedback.Please stop using 120v rated devices on a grid that can go up to 253V.I'm not sure what your ripple control system is/does?Dimming lights depends on the type of light. LEDs? or CFLs?Is the strobing effect a status warning indicator?

author: nzmikec
author_rank: Contributor
timestamp: May 30, 2020, 02:53:30 am
content: Thanks for your reply and I acknowledge your concerns re the grid voltage.I have however checked to ensure that all power handling components of the switch are certified for use on a 240v grid. The switching triac is rated 16a 800v, relay and caps etc at 250v. Im open to being told this is not safe however I would like to know the rationale given the components are up to the task.I am dimming LED's using leading edge dimming. The switch allows for leading or trailing edge dimming strategies but I have had best results with leading (Standard for AC LED's I believe). Nothing is listed in the WEMO manual for strobing and like mentioned earlier it occurs on a time of day schedule which is leading me to the ripple control theory.My grid is PowerCo. They use Ripple control for load management including on customer premises loads like hot water and other loads like street lighting.https://www.hotwatercylinders.nz/blog/what-is-ripple-control/Kind regards,Mike

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 30, 2020, 04:01:55 am
content: Quote from: nzmikec on May 30, 2020, 02:53:30 amWithout knowing the circuit I can't be sure, but if a capacitors is unipolar electrolytic then it wouldn't be suitable with 240Vac on it for these reasons.1. Reverse bias (But for this circuit they are probably used correctly as DC caps).2. Peak voltage will be sqrt 2 * mains voltage. These would normally be rated.3. Your grid voltage can easily and legally get to 253Vrms if your neighbours are generating solar.4. Capacitors need a bit of headroom in the design, probably 150% - 200%.5. Common sense would tell you that if the switches/design could've rated at 240V then they would have been.Also if that is a MOV then it may be in its conduction zone at the higher voltage, possibly due to the ripple control? Also probably why the fuse blew.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: May 30, 2020, 08:03:35 pm
content: Quote from: nzmikec on May 30, 2020, 02:53:30 amusing a 250 volt cap for a 240 volt nominal system. +/-10% pushes the RMS voltage to 265 RMS and 369 volts peak. So it's a bad idea.

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2020, 10:12:38 am
content: nzmikecHad an interesting chat with my sparky buddy just a few days back concerning uncertified appliances/fittings usage in NZ where his customers had imported and installed fittings not approved for NZ usage.If they fail and start a fire and is proved they were the source of the fire you have zero insurance !Please don't let that happen to you.