I administer or help coordinate a number of US groups that review IEC standards to develop proposals and positions on drafts. I am always looking for more willing participants to help in this review so that the US position is as representative as possible of industry, users and general...
The requirements in UL 499, Standard for Electric Heating Appliances, is for 3/8 inch through air spacing and 1/2 inch over surface spacing between field wiring terminals. The CSA requirement is probably roughly equivalent. This requirement comes from table 25.1.
For the voltage referenced...