I've recently replaced a standard 3-pole switch with the Honeywell RPLS540A programmable switch. The product says that it is not compatible with CFL or LED lighting. I foolishly did not read the fine print and only discovered this after installation. I had two overhead CFLs and they flickered when the switch was turned off, which I came to learn was due to the issue discussed here. I've replaced the CFLs with LEDs and everything seems to be working fine despite the claim of "incompatibility" with both CFLs and LEDs. Is there any reason that this setup has created a potential safety/fire/shock issue? Or if things are working normally can I be reasonably confident that I'm okay?

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    I imagine a "selling feature" of this switch is that it does not require a neutral wire? It's possible you are dealing with an LED that is so smart it knows how to coexist with this shoddy obsolete design. – Harper - Reinstate Monica Jan 9 '18 at 20:21
  • It is the case that the installation wiring diagram does not show a neutral connection and there are only terminals for the load, line, 3-way, and ground. So, if I understand correctly, the device requires 40 watts, but can only draw this power by passing the current on to the load (because it does not wire to neutral). This is why the CFL flickered, but the LED bulb is ostensibly smart enough to ignore the reduced current even though it’s only a 9w LED. Is that what you’re suggesting? I’m a pretty green novice so I just want to be sure I have my head around it. – stexeeb Jan 9 '18 at 22:39
  • Correct, this era of device powers itself by placing itself in series with an incandescent bulb of at least 40W. An incandescent bulb which is not lit, more or less resembles a dead short, so in "off" mode, only a tiny current is needed as the device is gulping most of the voltage drop. CFLs and most LEDs respond oddly to this tiny current. – Harper - Reinstate Monica Jan 9 '18 at 22:45
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    UPDATE: Oh well, so much for that. Now in the dark I see that the LEDs are also dimly lit. I guess I'll need to go with old-school incandescents. But thanks very much for the info! Good to know for the future. – stexeeb Jan 9 '18 at 22:46
  • It will suffice if only one bulb is incandescent. There was a time when color matching LED and incandescent would have been hard, now it's easy. – Harper - Reinstate Monica Jan 9 '18 at 22:53

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