I have a board (Krida electronics, not mine) that uses 2-pole PCB screw terminal blocks with 0.2" (5mm) pin spacing for Line & Neutral input. The conductive parts inside the block are very close together. Worst case scenario, there could be a 0.0275" (0.7mm) air gap between conductive parts. As a hobbyist, this normally freaks me out (I usually leave 5mm air gap for L-N separation).
Is there an equation or UL spec that I can use to calculate if this gap is safe?
Also, before someone suggests this: If this was a permanent installation, I would insulate the terminals with hot melt (assuming the device didn't hear up too much)
Best Answer
0.7mm of clearance is pretty small. If functional insulation is all you are really required to have from a primary to a primary, then 1.5 mm is sufficient.
The online calculators at http://www.creepage.com/ are pretty faithful to the IEC (or UL if you prefer) 60950 specification, which dictates safety measures for Information Technology Equipment.
(edited from 1 mm to 1.5 mm. I didn't take into account that the peak working voltage would be as high as mains voltage)