Here is the Pages from the magazine:
The relay board chosen for switching the mains in this project is the ‘Spark Fun Beef Cake Relay’ which is fitted with a JQX-15F 005-1Z1 which according to the QX-15F Datasheet is switched using 5V DC and the PCB mount SPDT contacts are raited to switch 20 A at 240 VAC (Form C).
So thats all good, for switching a 230 VAC 3 kW kettle (approx 13 A), however the guide doesnt cover how to wire the kettle to the relay in a safe way, At minimum I would suggest putting it in a plastic box and keeping fingers away from it at all times.
I havent had a good look at the Spark Fun Beef Cake Relay to see what the PCB is like, but I fear that the tracks on the PCB may not be raited for the full 13 A load.
Also I don’t know how the project deals with kettle being off when you want it to boil (I suspect a hairband would work).
I am going to be doing something similer with my sous vide cooker using a solid state relay.