On Tue, 10 Dec 2013 09:54:20 -0800 (PST), "
wrote:

On Tuesday, December 10, 2013 11:30:17 AM UTC-5, Jennifer Murphy wrote:
On Tue, 10 Dec 2013 05:45:31 -0800 (PST), "

wrote:



If the box has no neutral, then there is no code compliant
way to make the switch that requires it work. The issue is
that a programmable switch needs to be powered somehow. That
could be by a battery, through the hot and neutral, or by
using the load circuit. The latter is why the other switch
has a minimum load of 25W. Without some kind of minimal load
for a small current to flow through and power the switch even
when it's off, it would have no power. That small current flows
through the bulb when off and it's enough for thw switch, but
so tiny it won't light the bulb at all.

The minimum it said it needed was actually 40W.

Does the switch really draw 40W for its own use?

No, it draws negligible amount of power. If it drew
40W the box would over heat. It's just that with no
neutral, the switch winds up getting it's power in
series with whatever the load is. With too small of a
load, the switch can't get the necessary voltage/current
that it needs.

If the switch obnly needs a fraction of a watt to operate, why does it
say that the load must be at least 40W? Why couldn't it get ebnough
power with a 5W bulb as the load. 5W is much larger than a fraction of a
watt.

I should have paid closer attention in freshman physics.