florinc:
Isn't a current sensor, like this one
http://www.seeedstudio.com/depot/noninvasive-ac-current-sensor-100a-max-p-547.html?cPath=144_154
a much safer and reliable option for this purpose?
I am aware of these and I use one for hvac power consumption monitoring/ logging. For the particular use I am more interested in weather it is ON or OFF, so I was looking for a cheaper solution. When I draw the line at the end, I may still end up using a CT.