1) RIMS (Recirculating Infusion Mash System)- This is a system that uses a wort pump along with an enclosed electric heating element with PID & temp probe to keep the mash at a constant temperature. It is a pretty slick system if you have never seen it and is relatively compact in size when you do not include the wort pump. Usually this is made of stainless steel pipe and tee fittings that enclose the heating element and temp probe. The constant flow of wort through the RIMS tube help keep the wort flowing and the temp stable. Some of the cons for this is that first off you have the price at putting this altogether. I estimate it would cost around $250 to put a nice one together (excluding the cost of the pump). Also some people are concerned with the electric element scorching the wort as it passes by it. This may or may not be true and can be greatly reduced if you have the wort being pumped constantly through the RIMS.
Here is a link to a quality PID on Amazon.
2) HERMS (Heat Exchanged Recirculating Mash System)- This is an immersion style of a heat exchanger except you are using your HLT with hot water to help increase or stabilize the temperature of your wort. This uses the water you planned on sparging with to heat a copper or stainless steel tubing that is in the HLT. A temp probe it the mash tun would switch the wort pump on and off to help stabilize the temperature. Some have it so that the pump is constantly running and the temp of the HLT is monitored with a possible solenoid valve on the gas burner to turn it on and off. The cons of the system are again the cost of assembly. Also the addition of tubing in your HLT may be a pain to install. The use of gas to regulate the HTL can be worry sum also as I can see the HLT temp spiking and the mash temp going with it.
Here is a great article from BYO.com on the subject : RIMS and HERMS Brewing
3) Gas or electric direct heat- This is where there is a burner under the mash tun, or an electric element ported through the side. This is putting direct heat on the mash. This may be one of the cheapest ways to go about it, but I feel the most dangerous. Unlike the RIMS unit that also has a heating element in it the straight ported element does not have the benefit of the pump moving wort around it. If the wort is sitting on the element with no flow you could end up scorching the wort…and especially with pale ales this is bad. The gas burner also has the same risk with the wort and grain sitting on the bottom of the mash tun. You really need to be careful if using this as a way of maintaining the temp.
Here is a link to the gas burner I use on my homebrew stand. Natural Gas Burner
4) DO NOTHING!- So you are short on funds and just want to get brewing. You can skip trying to regulate your mash tun and just let the temp slowly drift down as it cools off over the normal hour of mashing. It has been noted that the majority of the starch conversion happens within the first 15 minutes of the mash. In an environment with an ambient 72 degrees a 154 degree strike temp may only drop to 150 over an hour. You can safeguard against temp loss if you insulate your mash tun. That is why many people use large cooler as mash tuns to help reduce temp loss. This is a great idea for a new all grain brewer or someone that does not want to get to serious.
