Going from 21C to 0.5C takes about 10-12h depending on ambient temperature and temperature of the glycol reservoir (I have it at 4C during fermentation, set it to -3C for cold crash).Dues it take long? Guessing about 20mins?
That's what I did before switching to use the ice maker compressor, I just filled a cool box with ice accumulators in order to keep fermentation temp. With the added compressor I don't need to worry about changing the ice accumulators anymore :).Tbh with the twister coil, you could run this on a good ice box. If you wanted temp maintenance.