Offline SMPS: Clearance from Earth net?

[cupoftea]

Hi,
In an offline isolated Flyback of 20W (24VOUT), we have an earth screw going through the PCB right in the middle of the isolation barrier bit.
But since its earth, presumably it can be within 2mm of any net on pri or sec side?....because after all , its earth....and if it contacts line or neutral, then the fuse will blow.

 

[Easy peasy]

3.2mm from earth to P or N assuming low pollution degree environment

 

[FvM]

Question is if you must consider possible PE discontinuity. If so, reinforced insulation required.

 

[cupoftea]

Question is if you must consider possible PE discontinuity. If so, reinforced insulation required.

Thanks, there is an insulated Earth wire soldered to a pad right next to it, and joined to its screw pad...the Earth wire's other end is soldered to the EARTH net at the mains input.

3.2mm from earth to P or N assuming low pollution degree environment

Thanks its interesting , i had this before in a different company, where they had Earth 0.5mm from pri side nets, and also same earth 0.3mm away from sec side nets....so overall, there was kind of just 0.8mm clearance between pri and sec side nets....i pointed this out, but was told not to be so daft..."its earth, if it contacts something, the fuse will blow"........and "what do you think happens when there's a fault, Earth and Line are supposed to be directly in contact, so that the fuse can blow".

I haven't seen it referred to in IPC2221, and i think i will need some official reference to refer to for this.
Please does anyone have the ref?

 

[FvM]

I'd refer to IEC 61010. For reinforced insulation double the clearance.

 

[cupoftea]

Thanks, ive saved that, thoigh i must say it says line_to_neutral.......i appreciate that creepage is the thing...but when earth is involved kind of "in the creepage path", then , i am told, things are different, its not so strict....because after all......when a product is in fault...the line and earth are supposed to be directly in contact anyway.

Its kind of hard to argue with somebody about clearance/creepage between line to earth...when those very things must be directly in contact during a fault....i mean, how can you then say, that they must be spaced apart from each other by a certain amount.?

I am seeking our previous discussions on here about this from approx first half of 2020