Anova Precision Cooker did not turn off

[kojak]

Not sure what I did wrong. I set the temperature and the timer and started the machine. It was set to run for 2 hours.

When I returned about 4 hours later the timer was down to 00:00 but the temperature was still at 150º F and the water was still circulating.

I thought that when the time expired the water temperature would also begin to cool. That way nothing would overcook.

What am I not understanding?

[fischersd]

The timer doesn't turn the unit off. You want it to hold the temperature so your food doesn't dip into the danger zone (40-129F)

Sous vide cooking (with a few exceptions, such as eggs and fish) is remarkably forgiving. Most meats you cook for many hours, so forgetting / getting tied up with other things doesn't ruin your meal when you get back to it a little late.