Chris P. Bacon What fuses are running in your RCD? I use a 2 way consumer unit with 6amp for lights and 32amp for sockets. If you have a 32 for sockets it shouldn't trip out. Just add your sockets up (add plug amps which are being used) and see if it accumulates to more than your fuse in consumer unit, if it equals more than unplug something while you use treadmill
Szabolcs Borbély Szabolcs Borbély Probably you've got a power surge in the treadmill somewhere. Your home has differential circuit brakers (these will be tripped if there is a difference more than 30 mA - usually - between the pahse and null lines), your parents only the conventional ones. If you disconnect the earth line, the power surge to the gorund is interrupted, hence no braker tripping, but this is dangerous! You actually have power on the metal frame of the machine!