Creepage and clearance of through hole resistor on LIVE PCB trace

Thread Starter


Joined Sep 11, 2012
Recently I found a resistor broken on a PCB. It is a MOF type 1/2W through-hole resistor. I found that the resistor is directly placing (touching) on a PCB Live trace and I know that the potential difference between the resistor and the trace is about 220Vac. There is a small hole on the resistor and a burning mark on the PCB trace. Therefore I presume an electric arc was formed between the resistor and the PCB.

Then I read the safety standard EN60335-1. For the part describing creepage and clearance, it has a remark: "Lacquered conductors of windings are considered to be bare conductors" As I know common MOF resistor body is just a lacquered coating,

I would like to ask is this resistor considered as "Lacquered conductors of windings"? If so this is violate the safety standard.

If this is not, is a MOF through-hole resistor body touching a Live PCB trace violate the standard?

Appreciate if you can provide strong supporting document or information.

Thank you very much