I keep frying resistors in the following optocoupler and triac snubber circuit, and I'm not sure whether to attribute this to bad design, or to faulty components.
- There are no observable sparks at turn-on, but the 680-ohm resistor burns out within seconds.
- I'm using 1/4W through-hole resistors.
- The power triac gate triggers at <= 35mA.
- The load is a ~50W fan that runs on mains power.
If my understanding is correct, the steady-state (ON) power dissipation of the 680-ohm resistor should be less than 0.1W.
If you agree that my design is reasonable, then what component do you suspect is faulty, and why?
I also tried the following circuit, but again, the 680-ohm resistor smoked when I put the optocoupler in the ON state: 
Answer
I suggest you read TI app note SLUP100, "Snubber Design" by Philip C. Todd for some good background on snubber design.
When the triac is on, the dissipation through the snubbers will be low since they are 'shorted' by the triac.
When the triac is off, load current is going to try and flow through both of your snubber circuits, and the resistors are going to see power dissipation.
Are you absolutely sure that the triac is firing each cycle?
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