We are developing a household device, which consists of a +48VDC power supply and a PCB, where everything is located inside a grounded metal frame. The only parts that come out of the metal frame is a CAN connector and the Power Inlet for 230VAC.
According to IEC 60335 for household devices, the surge voltage is +4kV (level 4) for the power line and +2kV for other I/Os, which means that I need good protection for my PCB.
As a power supply, we are using the UHP-750-48 (https://www.meanwell-web.com/content/files/pdfs/productPdfs/MW/UHP-750/UHP-750-spec.pdf), where already the first problem occurs. This power supply is only tested for surge voltage up to 3kV and the same for EFT. Now there seems not to be really many power supplies in this power class, that have level 4 protection for this except medical power supplies and I'm really questioning what I can do to pass this level of protection.
If the power supply lets some disturbances to the +48VDC line, I need to protect the PCB itself. At the moment, I protect the input with a 8.0SMDJ54A TVS diode and a lot of ceramic and bulk caps, but I'm unsure if there would be a better protection? For EFT this should be fine, but for the high 4kV surge pulses, I think it will blow up, but I have never tested a circuit before on this level.
For the CAN bus, I use the following protection:
Also here, this is mostly for EFT and ESD, but I also doubt here, that it will be enough for 2kV surges. Also on any bus voltage, there are TVS diodes, everywhere are decoupling caps and also on any connector there are TVS diodes.
So my questions in the end are, how can one properly protect a PCB from the surge pulses and second, how can I solve the problem with the power supply?