Introduction: Temperature Control of Ss Brewtech 7 Gallon Conical Fermenter

Step 1: Goals

There are a number of solutions to maintaining constant temperature of your beer wort during fermenting. My goals in this project were to:

  • · Use my existing Brewtech 7 gallon fermenter (with mods, of course)
  • · Keep it easy to clean (i.e. don’t add insulation, coils, fittings, pumps, etc.)
  • · Maintain the current gravity flow process from kettle to fermenter to keg
  • · Provide an energy efficient cooling process
  • · Use off the shelf components wherever possible
  • · Be good looking and compact

The most obvious solution for cooling something is to put it inside a refrigerator. But to fit inside the limited space of my brewery and to look good, I wanted to use a counter height refrigerator. There are dozens of models, but the ones that are best suited are the wine coolers. These do not have an ice maker, so after removing the shelves, the entire inside volume can be used. I picked a Frigidaire Model FFWC4222QS-1 which was on sale for about $250. This unit has a glass front door which is reversible. I changed mine to open to the left since the kettle is to the right. I am not sure this model is still available, but all of the wine coolers are more or less the same size. The inside dimensions are never given, so you will need to measure them yourself. The most critical dimension is the overall height. This is 26.5 inches. As you will see, I managed to make my Brewtech fermenter fit this height with about ¼ inch to spare.

Step 2: Mechanical Modifications

By orienting the back two legs against the front of the compressor compartment at the back of the refrigerator, there is plenty of room front to back and side to side. But the overall height is 37.5 inches so we must eliminate 11 inches.

Starting at the top, we can replace the standard dome shaped cover with a flat cover, FE800L from MoreBeer ($35). The plastic airlock is replaced by a piece of ½ inch ID flex tubing that will be submerged in a beaker of water and connected to the lid using a ½ inch “blow off” elbow, FE870 from MoreBeer ($18). However, the flat lid comes with the required 5/8 inch diameter hole on its raised surface. We gain another ¼ inch by filling this hole and drilling a new one in the recessed center portion of the lid. This is a job for a stainless steel fabricator who will make the new elbow for the trub dump. I live in Mexico where such work is very reasonable. The lid modification cost about 300 pesos ($15).

On the bottom of the Brewtech Fermenter, we can reduce the length of the legs, but this should be done last. To gain the overall height reduction needed, the 1-1/2 inch diameter elbow used for the trub dump must be replaced with one having a right angle. The easiest way to make this part is to buy a 6 inch long tri-clamp sanitary spool, SP-150-006 from Glacier Tanks ($20). The part is cut at a 45 degree angle and welded back together as shown. This is another job for the stainless steel fabricator. It cost me about 500 pesos ($25). The dimension shown 60.28 mm (2-3/8 inches) is important. If it is much longer the fermenter will not fit in the refrigerator, but if it is much shorter, the triclamp will not fit around the upper flange on the part. A comparison of the original and new 1-1/2 inch triclamp elbows is shown.

Assemble the right angle elbow and the dump valve on the fermenter and measure the vertical clearance below the lowest point on the valve to the surface supporting the feet. Subtract about 1/8 inch minimum for clearance. This is the amount to cut off all three legs. Remove the plastic feet and fit them back on the shortened legs.

If you have done everything correctly, the fermenter should fit nicely inside the refrigerator with about ¼ inch to spare.

Step 3: Temperature Controller

Wine coolers have a temperature range of 41 to 64 degrees F. This is too cold for most ales, but we can use an external temperature controller. I picked the Bayite TCF-3A017 because it is made to sit flat on a surface like the top of the refrigerator. Amazon sells these for $18. To make a neat wiring job, use a waterproof electrical box with threaded holes on the two opposite ends that will accept cable clamps. The outlet can be a combo unit with a switch (Leviton #5225). These are all available locally. The line cord can be a molded 3-conductor AWG 16. Wire the controller to the junction box as shown in the schematic using 12 or 14 gauge wire (you will need about 2 feet each red and white, and 4 feet of black).

The temperature controller comes with a probe that must be put inside the thermal well on the fermenter. You will need to drill a small hole through the top of the refrigerator for the cable. But first use a voltage probe to see where the wiring inside the refrigerator is so you don’t drill through a wiring harness. On the Frigidaire, the wiring runs along the right hand side of the top (viewed from the front) then along the front edge. So anywhere on the left hand side about half way back is a safe location for the hole. On other refrigerators, you should power the unit on, then run the probe along the inside of the top surface to see where the wiring is located. Put some silicone over the hole to seal it and keep the probe wire in place.

To hold the probe in place on the thermal well, use a plastic cap, McMaster 9753K42 ($5.31 for a package of 100) with a small hole drilled in the end. This makes the probe easy to remove when the fermenter is taken out for cleaning.

Step 4: Operation

With this setup, you may have to modify your brewing procedures slightly.

During fermenting, run a ½” ID flexible tube from the upper blow off elbow across the lid and down the front right hand side of the fermenter to a beaker of water. (Orient the lid correctly for this). I like to use the high flex food grade tubing from McMaster Carr. Their part number is 5229K63 ($10.50 for 10 feet). See the photo at the beginning of this instructable.

To transfer from the kettle to the fermenter, it is best to use some sort of inline cooling. I used a 40-plate type counterflow chiller made by Duda Deisel. With a moderate transfer rate (15 minutes for 5 gallons) this cooler brought the hot (190 to 200 degrees F) wort down to 76 degrees inside the fermenter. The refrigerator will take the temperature further down at a rate of about 1 to 1-1/2 degree per hour. I also used an in line oxygenator, Part Number B07D9CPGC3 on Amazon for $18.99.

To add the yeast, hold the ½” tubing above the top of the fermenter and use a 4 inch funnel, MoreBeer BE491 ($4). Since I use a yeast starter with a magnetic stirrer, I put a screen (MoreBeer BE497 - $1.79) inside the funnel to catch the magnet. Be sure to unlatch some of the latches on the lid to break the seal while adding the yeast mixture. Otherwise the air inside the fermenter will make the yeast transfer difficult.

When dumping the trub, screw a 3/4x5 inch stainless steel nipple into the dump valve. You can get this from McMaster as 4830K197 ($7.76). This lets you catch the trub in a bucket outside the refrigerator. Be sure to remove the 1/2“ vent line from the water when doing this to avoid water being drawn up into the fermenter.

Step 5: Performance

The first graph shows the wort cool down inside the temperature controlled fermenter after transfer using the in-line counterflow chiller. I pitch the yeast at about 77 degrees and ferment at about 67 degrees.

If you use an immersion cooler in the kettle, the wort will transfer into the fermenter at about 87 degrees. Now the refrigerator will run about 7 hours to get to the yeast pitching temperature as shown in the second graph. In line cooling is definitely better.