A number of people on the forum recently purchased the Mamac CT-800 switches posted here. I received mine last week and thought I would document my work as I installed them in my Washer, Dryer and Furnace. Please only use this as a guide. I am not an electrician and you should always check with your local regulations regarding making these kinds of modifications to your home. Only follow this guide if you feel comfortable around electricity. 220VAC can definitely hurt you so be careful.

How the CT-800 switches work: In layman's terms, the CT-800's are a current transformer with internal circuitry to open and close a set of contacts, based on how much current is flowing through them. This particular model will have its contacts "open" when less than 1 amp is flowing, and "closed" when 1 amp or greater is flowing. Most devices like your dryer motor, furnace fan motor and washer motor use at least 1 amp while operating which makes the CT-800 perfect for this application.

Without getting too technical, the number of turns of wire through the CT-800's center is proportional to the threshold at which the CT-800 closes its contacts. If you run your wire straight through the center of the CT-800, the contacts will close at 1 amp of current flow. If you put your wire through the hole and then wrap your wire around the outside of the CT-800 and back through the hole so that the wire actually goes through the center twice, then you have cut the current required to close the contacts, in half.