Re: Minimum clearance for 230V AC.

piglet wrote:

Chris Jones wrote:

Pimpom wrote:

What's the minimum surface clearance you consider adequate for 230VAC,
on FR4 without slots or added creepage? Forget about IPC-2221 unless you
base your layout strictly on it.
>
Personally, I try to maintain 3mm edge-to-edge between tracks and pads,
more if space permits. What do you think?

>
The distance along a surface is called creepage in the standards.
>
The required distance depends on whether the insulation is supposed to
be single insulation (functional, basic or supplementary) or double
insulation (reinforced insulation).
>
Basically, if the insulation failing ought not to kill someone because
the part that would become live is either protectively earthed or
separated by supplementary insulation from the user, then a smaller
creepage is allowable.
>
If the insulation failing could immediately give someone a shock because
there is no protective earthing or supplementary insulation, then a
larger creepage distance is required.
>
The exact distances required in different standards tend to be
different, though I think a lot of different products that used to be
subject to different standards have recently been grouped into one set
of standards, IEC62368-1.
>
There are some tables here:
https://www.powerctc.com/en/node/4757
>
I think you are going to come up with something like 2.5mm for basic
insulation and 5mm for reinforced, but you should check carefully what
the standards say, and for some classes of equipment it can be much
more, like 6mm or 8mm.

>
I’d also want to consider if the pcb tracks are naked or covered with
solder mask or conformal coating .

This photo shows the underside of a two phase HVAC PCB:

<https://crcomp.net/misc/hvac.png>

This particular PCB's pulled from the Heating and Air Conditioning unit
from one motel room in a chain franchise. It's found, one PCB per room,
in motels and hotels throughout America. In other words, it's acceptable
to appropriate authorities.

If you look at the dark defect near the left edge you can see part of
the conformal coating melted away.

Relays are located at near the bottom of the PCB. The larger gaps
measure about 3mm and separate phase voltages from each other. The
smaller gap measures about 2mm and separates one phase voltage from
neutral.

Long story short, your 3mm separation seems adequate, IMHO.

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.