A Recirculating Infusion Mash System (RIMS) is a system to precisely control the temperature of the mash process in home brewing beer. RIMS offers an advantage over simpler methods of making beer because of the ability of a RIMS system to precisely hold mash temperatures, especially important during step mash processes. Beyond the shared elements of heat exchangers and pumps, these systems vary widely and show the personality of the builder, usually the home brewer himself. Before starting your own RIMS build, study as many systems as you can and plan carefully, keeping safety and ease of use in mind.
Decide whether to build a wooden or metal support for your system. Either works well with an all-electric system, but metal is better for a gas-fired brewery. Which ever you choose, build your stand to support the weight of at least 20 gallons of water, or 72.6 Kilogram.
Determine the location of your RIMS system. It should be close to the electrical supply to avoid long runs of power-robbing wire. A water source is also convenient, but not as necessary unless you are planning to use a counter-flow cooler for cooling your wort.
Build the heat exchanger using a heating element designed for a hot water heater. The available amperage to your brewery will determine the maximum wattage of the element you can use. The body of the exchanger is typically a section of copper tubing, large enough to house the heater element. Drill a 1/2 inch hole on one side and near each end of the tube and solder in a piece of 1/2 inch diameter copper tubing to act as a pipe nipple. Solder a cap on the end of the tubing opposite the heating element, making sure the cap is leak proof. Finally, insert the heater element in the open end of the tubing and screw and epoxy it in place. The fit must be leakproof when completed.
Using the correct sized wire for the amperage your element will draw, connect the heat exchanger to a solid-state relay that has contacts rated for more amperage than your heating element requires. A digital temperature controller, which can be purchased locally or from auction sites such as eBay, controls the switching of the relay, turning the heating element on and off as necessary to maintain the selected temperature. Place the thermocouple from the controller in the system where it will be in constant contact with the wort; many people suggest that the best location is in the pipe between the mash tun and the pump.
Select a magnetic drive pump with a stainless steel or composite impeller and housing that is rated for boiling temperatures. Mount the pump below the bottom of your mash tun. Wire it to run constantly when the system is plugged in. A ball valve should be fitted with a pipe nipple on both sides and inserted in the tubing between the pump and the heat exchanger. Regulate the flow from the mash tun with this valve.
Use a cooler for the mash tun to reduce the amount of time your heat exchanger runs. Typical coolers for this use are the five and ten gallon coolers available at department and home improvement stores. Replace the drain valve with a hose nipple or quick-disconnect pipe fitting. The seal between the nipple or fitting and the cooler must leakproof.
Plumb the drain from the mash tun to the pump inlet. Plumb the output side to move the wort through the heat exchanger and back to the top of the grain bed in the mash tun. Make a manifold of copper tubing or CPVC pipe to spread the flow from the return line as evenly as possible over the top of the mash. This avoids channelling and puddling. Add valves and additional plumbing as desired to move the wort to the boil kettle using the same pump. Gravity can accomplish the same thing in a simple RIMS sytem, reducing cost and complexity.
Electricity and water is a dangerous combination. Plug your RIMS system into a ground-fault interrupter (GFI) receptacle, making certain that the GFI is rated for the load.