ChristophW

kmpres, I believe what you saw can be caused by induction (or some kind of electromagnetic effect). For example, if the wire serving this light runs parallel to other live wires, I believe you will get some measurable voltage. However, you will not get much or any measurable current because the parallel wires are some magnitudes shorter of what you would find in a transformer.

Also, please note that just because the light is off, this does not mean that there are no hot wires in the light fixture. The switch might be installed in the neutral wire (relative to the light fixture). So while no current can flow through the light because the neutral wire is interrupted, if you touched the hot wire you personally plus your aluminum ladder would "close" the circuit against ground. Not sure if such wiring is against (Japanese) code but would you trust your contractor and bet your life on it? Therefore, ALWAYS turn off the breakers and get an extension cord and work light.

One more comment on the iVac (see my previous posting below). I noticed that the specs say it supports two circuits and with a built-in, resettable 12A circuit breaker each. However, 12A are not enough for some more serious power tools like my benchtop table saw. I contacted MBright and the person said, they have to write 12A because the 'Certification UL/CSA lab' requires that (no tool plugged into a 15A circuit should take more than 12A), but the circuit breakers in the iVac are in fact 15A. No need to cancel my order :-) They are supposedly also planning for additional products this summer that support higher amperages and voltages.

fpratt, for a while I had been mulling over the same question. My table saw draws a max of 15A, but with my big shopvac that would trigger the circuit breaker when I cut into thick lumber. For that reason I have already put in multiple, separate circuits in my shop and currently control both tools manually.

I found it weird that all those master-slave switches that can supposedly be used for power tools don't support separate circuits. Makes them look like toys.

Long story short, today I finally found what I was looking for all that time, the iVac switch from MBright Tools. Costs little more than the i-Socket switch and supports two separate circuits up to 15A. I haven't tried it yet myself but the order is placed :-)

As the author stated, to some people it does not make sense to use a fossil-fuel consuming product to replace fossil fuel consumption. IN my opinion, you have to look at the savings and if there are significant savings in total fossil fuel consumption (also compared to other insulation technologies like blown cellulose), this alone will justify a technology like foam insulation.

In our 1905 three story home in New Hampshire last winter we had 4" closed cell foam sprayed under all the roof area, which spans the third story plus another attic floor. Additionally, we had some of the accessible wall surfaces sprayed (e.g. where we just did demolition). Shortly after Before the house was absolutely drafty and you could feel the wind blow through. Afterwards, the upper floors (incl. attic with all doors closed) stayed cozy warm.

We cannot truly measure the impact of our improvements because we also got the windows replaced and other work done in Janruay and February, and for days at a time we had "things" open and the heat running. However, just from a living comfort point of view, the foam insulation makes a huge difference. Just as in winter time the upper floors stay warm (even though heat rises not necessarily a given due to only two heating elements, a closed door between 2nd and 3rd floor and the large roof area), the upper floors did not significantly heat up during those few hot days in NH 2009 (I know because that's where my office is.

Next winter we'll be able to report on the total savings of our improvements.

@bfield: No experience with that but from what I know the cost is in the material. Labor is minimal compared to that. The combined price from all that I saw is usually around 1$ per inch per sqf (will vary slightly on the foam type and manufacturer). I found a DIY kit online (don't remember the link) that comes in two "propane" tanks. The price down the sqf and inch thickness was basically the same as the professional installation. One problem is that the tanks and the gun cannot be recycled -> waste and cost overhead. So unless you need to just insulate small areas, it's probably not worth it doing it yourself.