Heater with PTC element an buss system

An electrical heater comprising:

• a substrate;
• first and second electrically isolated busses disposed on the substrate the first and second busses electrically coupled to generally parallel conducting element portions arranged in a generally rectangular pattern;
• a first voltage terminal coupled to the first buss and a second voltage terminal coupled to the second buss, the first and second voltage terminals located diagonally opposite each other.

In an electrical heater comprising an insulating substrate having first and second conducting elements disposed thereon interconnected by a positive temperature coefficient material, the improvement comprising:

• the first and second conducting elements arranged substantially symmetrically in a generally rectangular pattern;
• a first voltage terminal coupled to the first conducting element and a second voltage terminal coupled to the second conducting element, the first and second voltage terminals located in diagonally opposite corners of the generally rectangular pattern.