Crockpot BOILS the food!!!

I've had crockpots in the past and realize I should not have given away my first one, which had a temperature control from 20 to 500 because it doubled as a deep fryer. Recently I bought a 6 qt one because I wanted the extra size and the oval shape for large items. It has only low, high and warm. This is a Crock Pot brand, the original manufacturer so I thought it would be a good buy. However, after it's on for about an hour, it starts boiling the food. I turned it to low when I noticed but it actually does not stop boiling --- the bubbles are just smaller!!! Has anyone had this experience? I'm about to give it to Goodwill and find one that has a more defined temperature control................