Hi,
I am currently designing a PCB which has a number of TRIACs and photocouplers, to be used for switching mains on and off for some devices. For some reason, I have never before had to use TRIACs for professional products, but I know how they work. That is not the problem.
My issue is that parts of my boards are slightly cramped due to wide tracks and the space needed between them. For creepage distances, I have mainly used IEC 61010-1, as this is the standard I am most familiar with. However, this standard is mainly concerned with personal safety, and addresses insulation between hazardous live voltages and operator accessible parts. It does not worry about insulation between phase and neutral.
Until now, I've used the distances for "Basic insulation", which is the "single" insulation distance between phase or neutral and e.g. earth. As an example, for mains voltages up to 300 V rms at maximum 2000 m above sea level, the clearance is 1.5 mm, and for PCBs with a CTI of 175 or greater, the creepage distance is the same. In most cases, I have used this distance on the PCBs, sometimes with a correction for altitude.
But now I had a close look at the TRIACs, which are in a TO-220 case. When a TRIAC is off, I'll have neutral (though the load) on pin 1, and phase on pin 2. According to the datasheet for the T2035-8I, the distance between the pins is between 0.84 and 1.4 mm. Even with this tiny distance, the T2035-8I is designed for a whopping 800 V!
So (finally) my question: Which standards, if any, do you use for creepage and clearance when working with mains voltages? I have found some detached tables here and there, but as this board is going to be used in professional equipment, I'd rather want to use an official standard from IEC or similar.
