I had the same issue when outfitting two homes with Insteon dimmers (which support both multi-location control and full home automation with an optional computer link) over the past 6 years. For CFL bulbs, it comes down to the design of the ballast. I used a combination of forum research and experimentation to find no-flicker bulbs, and have the following recommendations (in order of availability & price):
- TCP SpringLamp series
- Overdrive Lighting dimmable spiral
- EarthTronics / EarthBulb
- Dimmable CCFLs from LiteTronics or TCP (no high-lumen models)
All of them work wonderfully for me with a wide range of dimming and no flicker. One caveat: very low dim levels cause an audible whine on some of the bulbs, particularly the TCP models.
I've read about positive results with LED lamps as well, but the price isn't right (for me) yet.
If the bulb fits in the base, it is the right kind. It could be a problem with the fixture, but it could be anything else along the line as well, a bad switch, bad connection somewhere, faulty insulation, chewed by rodents, etc. RCDs are very sensitive, it doesn't take much current leakage somewhere to set them off.
If a careful visual inspection doesn't reveal anything, about all you can do is take various components out of the system until you find the one that was tripping the RCD. For instance, test the fixture by removing the wiring and connecting the wires to a simple keyless base with a light bulb installed. If the RCD does not trip and the bulb illuminates, then you know the fixture is at fault.
If the RCD still trips, then the fixture is not at fault. Next try taking the switch out of the system by wiring the switch wires together so that you have an unswitched circuit. Test again. If the RCD still trips, identify intervening junctions and connect your test light at each one, starting at the switch and working back towards the distribution panel. You will eventually make a connection that does not trip the RCD. Then you know the bad section is immediately upstream from the successful connection.
I've left out many safety details here in order to outline basic trouble shooting. If you are at all uncomfortable working on building electrics, do not do any of this, find someone that knows what they are doing. Also, if you have an older UK ring system, these confuse most people, you need to find someone familiar with this rather unusual arrangement.
Best Answer
If there is voltage at the fixture, inspect the sockets to make sure the contacts are in the proper position, and clear of debris (remember to turn off the breaker, Before sticking your fingers in the socket). Sometimes the contact inside the socket can get bent, and prevents the bulb from properly making contact when screwed into the socket.
If no bells and whistles go off.
If bells and whistles go off, replace the fixture (or have it done by an electrician, if you are not comfortable doing it yourself). If there are still no bells and whistles, you'll have to move to the switch to make sure it is functioning properly.
If there is voltage coming into the switch, but not going out of the switch (when it's on). Replace the switch (or have it done by an electrician, if you are not comfortable doing it yourself). If there is no voltage at the switch in either position, call an electrician to trace the circuit further.
WARNING
If at anytime during the procedure you see sparks, the breaker will not reset, or you just don't feel comfortable doing any of the steps, please contact an electrician.