Basically, a HE-Man RIMS system pumps the wort from the mash tun through a heat exchange coil in the liquor tank in order to set the temperature of the mash. The heat exchanger can raise, lower or maintain the required temperature for the mash.

The direction of the temperature change is dependent on the temperature of the liquor tank. Usually, your temperatures are increased while going through the various mash steps. Cooling is only necessary when you over-shoot a target temperature.

The system is a based on a typical three tier brewing setup that I purchased through Stainless in Seattle . Since Stainless in Seattle has gone out of business, may I suggest that you check out the Peak Brewing System at Homebrew Heaven . Their system is quite similar and it was a difficult choice for me when I was selecting a 3 tier system. I have had a chance to see their system in person and I would highly recommend it.