Anything I can do with a Solid State Relay ?

I acquired two of these in their original package from a box of parts that was in the Air Conditioning class. Both of them are Crydom TD2401 Solid State Relays by International Rectifier. A quick search on Google resulted in me finding out International Rectifier sold their Crydom division in the early 80s so these have been laying in the bottom of the box for a while. Crydom still exist but is now part of Schneider Electric (who I know owns Square D as well). This model is still being produced. Since it takes DC for the control voltage and most HVAC equipment uses 24 volts AC, the class just let me have it. There are a couple more in the box as well.



I haven't done much other than wire it in place of a light swtch to test it using a 9 volt battery to turn it on and off. I've also tried feeding an audio signal to it and made the lights strobe on and off with every peak but it requires the volume to be turned up very high.

I have seen them used in regulating heater banks in large chilled water AC systems. They use PWM to adjust the heat load. I guess it is not really suited to other applications but have a play with it.