Three Kettle Direct Fire Systems
How does a three-kettle recirculating system work?
In a three-kettle recirculating system, you have a heated kettle for boiling, a directly or indirectly heated kettle for mashing, and a third heated kettle for the sparge water (HLT).
With direct firing, the heating element is located in the mash kettle under the false bottom and heats the mash directly. You have to be more careful that the wort flows sufficiently so that the mash doesn't overheat or even burn. It's not that hard to do, but I only recommend it to advanced brewers who have experience mashing in a circulating system.
Remember, you'll need a controller to maintain the temperature of the mash. You'll also need to heat the sparge water to the proper temperature for sparging. You can do this manually, but it's good to have a controller that can regulate two elements simultaneously.
Advantages of a three kettle system
Of all the recirculating systems, the 3 kettle system has the highest efficiency and yield. With proper controller, you can also make a double batch by mashing the second batch while the first brew is boiling.
A well-planned system requires only 2 or 3 hose changes per session with minimal wort loss due to dripping. Try it this way first to see if you can live with it or where you want to use a fixed connection.
Tips for ensuring an adequate flow rate
- Mill your grains at around a 1mm mill gap setting. This is fairly standard when ordering milled grains from your local homebrew shop, but it doesn't hurt to ask.
- If brewing with large percentages of high protein grains or adjuncts such as wheat, oats, or rye, consider adding rice hulls to improve drainage.
- Always turn off the pump when mashing in. Make sure your heating element is also turned off, to prevent overheating.
- Stir well when adding the grains to the mash kettle.
- Use a 3-5 minute grain rest period before turning the pump and heating element back on.
- Close the pump output valve almost all the way and turn the pump back on. Slowly open the pump valve. Doing this too fast can compact the grain bed. Lastly, turn on the heating element
- Don't walk away! Stay close and keep an eye on your kettle, the wort can thicken and slow the flow rate during the mashing process. if you ever notice the volume of the mash kettle rising, you are pulling a vacuum under the false bottom. Stop the pump and stir the grain bed.
I recommend keeping things simple and connecting the kettles and pumps directly with silicone tubing. When you move from mashing to sparging, you only need to make two hose connections. Then when you move to the boil phase, you only have to move the pump input hose from the mash kettle to the boil kettle. If you're careful, you can limit spillage to a teaspoon or two. And at any point, you can just drain the lines into a bucket to empty the lines.
The adjustable height sparge arm can also be used for whirlpooling with the 400 micron brew bag as a whole kettle filter. This works wonderfully to filter out hops and hot trub, and allows you to fully mix the kettle contents and completely drain the kettle.
Don't forget that starting with the 85L size, I recommend switching to 1" fittings (elbows, tube extensions, tees, etc.) and 19mm ID tubing.
If you don't want to use the whole kettle filter method with Brew Bag, you'll have to rethink the design. You'll want to put a 45 degree racking arm in the front of the boil kettle (don't forget the valve). However, this means you lose the temperature measurement point for the kettle, but you can add a tee and thermowell externally in the whirlpool loop.
You probably want a dedicated whirlpool arm in the boil kettle. You might also want to add another 3-way valve to the pump outlet to avoid changing hoses when filling the boil kettle.
Finally, you should use at least one flexible silicone hose to connect the bottom drain of the MLT to the front port of the boil kettle:
For floor mounted systems, you can attach the pumps directly to the kettle legs with our pump brackets. Shown here with the 85 liter kettles. Always bolt the kettles to the floor with our foot mounting plates!