Heating appliance

A circuit includes a heating circuit 330, a detection circuit 320 and a relay 46, the relay having an input 322, an output 324 and a control terminal 326. The relay input is coupled, in use, to one of a live or neutral of an AC power supply. The control terminal, which may be a driving coil, controls opening and closing of a switching circuit 328 between the relay input and output in response to a relay control signal. The heating circuit, which includes a heater 100, is coupled to the relay output at a node 321 and is couplable, in use, to the other of the live or neutral. The detection circuit outputs a detection signal to a controller, MCU 48, based on whether a signal having a predetermined characteristic is detected at the node. A method of testing the relay in a heating circuit is also provided. Additionally, an electrical apparatus and method includes sampling a voltage based on an AC mains power supply signal to generate a sequence of samples, applying a low pass function to the sequence of values, and estimating a voltage of the AC supply based on the low pass function output.