We are using a capacitive power supply for one of our applications.
The X2 capacitor (330nF in this case) provides good reliability with respect to failing safely/open and good over-voltage withstanding capability.
So the question came up what to consider, when choosing the parallel bleeding resistor to prevent negating the properties of the X2.
Apart from calculating the resistance value (500k for ~1s discharge choosen) and power rating (0.5W choosen) which is pretty straightforward, what else is there to consider?
What about properties like
* Flame retardant
* Fusable type
* Pulse voltage rating
I would tend to select a fusible type at least. I am unsure about the pulse voltage and peak power ratings though. The circuit will be used in an industrial environment and thus will be tested against 2kV surge L-N and falls into over-voltage category II. Resistors that withstand voltages >2kV are like 20x6mm 4W types, which seems total overkill.
PS: Our customer would prefer not using a varistor for surge protection if possible, due to very limited PCB space. So it may be a good idea to rate the resistor accordingly. And yes, they would really like to have the bleeding resistor because its easy to touch the contacts after being disconnected.