Increasing value of snubber caps at AC switch ?

[roger2]

Great information in this thread

 

[I LIKE MUSIC]

A wirewound would be in series with the load if a capacitor would short and the switch is open. You will have a dim bulb tester, the resistor being the bulb?

Not exactly. The resistance of the filament in the bulb increases with the amount of current being drown and that makes it inherently current self limiting. This is not the case with a resistor.

For safety we always look at the worst possible case in terms of failure.

Let us say that the capacitor in the snubber shorts and at the same time there is an internal short in the piece of gear and the piece of gear is turned off. The snubber is across the switch contacts. All of the current is going to flow through the resistor.

Lets say there is a 120 Ohm series resistor in the snubber. Ohm's law tells us that a 120 volt drop across the 120 Ohm resistor will cause 1 amp of current to flow through the resistor.

This means that the resistor will try to dissipate 120 watts. This is not likely a good thing. There may be arcs, sparks, smoke and flame...

Okay the piece of gear may have a fuse, but what if it is a 5 amp fuse? It is not going to blow with only 1 amp of current flowing through it.

 

[gslikker]

Mentioning the dbt was just a way of saying it probably acts like a lamp
Myself I assume a more probable single failure which implies the resistor in series with some transformer in case the snubber is across the switch in series with mains.
(Such failure could occur having power off and the unit unattended).

 

[I LIKE MUSIC]

I understand, but the action of a resistor and a lamp are not the same for the reasons that I mentioned.

My failure example is a worst case example just to show what could happen, even if it might not be highly likely.