Credit:
This boiler is based on one developed by Ken Schwartz. Ken did all of the hard work developing the boiler proper. THANKS Ken! His web page, the Plastic Electric Brewery, is a "must see".

Advantages:

• No more propane to hassle with!
• The stirrer reduces concerns about scorching of the wort by the heating elements.
• With the immersion chiller, the stirrer moves the hot wort over the coils of the chiller and greatly speeds cooling.
• The chiller, with it's integral lid, helps keep junk out of the boiler during cooling. This aids greatly in keeping the wort sanitary.
• It's very cheap to boil water and wort with electricity- less than 25 cents where I live!
• Automated boiling is possible. A computer based controller is in the works. It will help eliminate boilovers and adjust the boiling rate to yeild the target volume of wort.

• Electricity can be dangerous. Don't attempt this project if your are not comfortable working with electricity. Ground all exposed metal parts and use a GFCI on each 120 VAC circuit!
• Boiling wort is hot and will burn you.
• Use a HDPE (hgh density polyethylene) pail with a marked wall thickness rating of "NRC 090".
• The HDPE is not rated for use at boiling temperature. It does get a bit soft, but still works well.
• Use lead free solder and use it sparingly. Clean the flux residue after soldering.
• Run a couple of acidified water boils before using the boiler with a wort. I used lactic acid to drop the pH to ~4.

I reinforced the walls of the pail with a layer of aluminum flashing covered by a wrapped layer of 1/2" mesh hardware cloth. The edges of the cloth were fastened together with twisted pieces of steel wire. Holes were cut to allow the heating elements and wort outlet fitting to protrude. I really don't think this reinforcement is necessary. Ken doesn't use any and reports no problems but this boiler is insulated and the insulation means the pail walls will be at a higher temperature than an uninsulated pail. Anyhow, it was cheap, easy to do and adds a bit of piece of mind.

The lower portion of the boiler (up to just below where the wood stirrer blocks fasten) was insulated with 2 layers of aluminum faced "bubble wrap" insulation. All edges were sealed with aluminum faced tape (NOT duct tape!) to avoid heat loss via convection currents. The outside of the aluminum is barely warm to the touch when boiling.

Pail Extensions:
The pail extensions provide a bit of added volume for containing the foam resulting from boiling all-grain derived worts. If you only brew with extracts, skip making extensions. The extensions were cut from the upper parts of two "spare" 5 gal. pails. Another strip of plastic liberated from the top of one of the pails is wrapped around the lower portion of the lower extension. This takes up some of the slop between the extension and the boiler proper. I first tried roughening all mating surfaces with fresh 100 grit sandpaper, cleaning with acetone, smearing all mating surfaces with silicone and jamming the extension/spacer into the top of the pail. It didn't bond well- polyethylene is notorious for its immunity to adhesives. The "final" solution is was to wrap the spacer with thick clear polyethylene tape so that a tight fit is ensured. The upper extension is a bit shallower than the lower extension- part of it's reinforcing rim was removed to increase it's diameter a bit. Again, polyethylene tape was applied as a spacer to ensure tight fit. The fit of the extensions, although tight at room temp., loosened a bit when the boiler was brought up to operating temperature. To make the joints secure, more polyethylene tape was wrapped around the joints. I don't particularly like using tape, but, it sure is handy, remains in place well and doesn't affect the brew.

The blade of the stirrer is made from two pieces of 3/4" copper rigid tubing. The pieces were slit longitudinally down the centerline, opened up a bit and formed into the "S" shape indicated on the drawing. The "S" shape is very efficient and fairly easy to form. A riveted and soldered lap joint was used to fasten the two pieces together. The stirrer shaft was constructed from 1/2" rigid copper tubing. A coupling was soldered to the end of the blade and a slot was cut in the lower end of the shaft/coupling to accept the top of the stirrer blade. The coupling acts as a bit of reinforcement for the joint. Finally, the shaft was soldered to the blade.

The top of the shaft goes through a coupling that's soldered to a 1/8" thick brass mounting plate. The coupling serves as a bearing for the shaft. The plate is fastened to the hardwood stirrer support with 4 screws. The protruding shaft is fitted with yet another coupling which acts as thrust bearing to hold up the stirrer. It has 6 longitudinal kerfs sawn about 1/2 way through the length of the coupling. A hose clamp is fitted over the kerfs and tighten to secure the coupling to the shaft. Atop the end of the shaft is a drive coupling made from a 1/2" copper end cap. It is also kerfed and gets a hose clamp to secure it to the shaft. A hole was drilled into the top of the cap to accept a piece of brass whose top was machined to fit the gearmotor's 1/8" dia. shaft. A locking screw secures the brass coupler to the gearmotor. The bearing surfaces were smeared with a bit high temp. grease. Don't overdo the greasing- grease in your brew is not good.

The gearmotor is made by Rowe and is speced 70 RPM at 12 VDC and 200 mA. Surplus Center (800-488-3407) carries them as item # 5-1162 for $5.95. I drive it with the same variable voltage DC power supply I use for my RIMS pump, however, a fixed 12 VDC power supply should work fine. I run the stirrer at 9 volts (about 60 RPM) during the boil and then run it full-speed after the wort temp. drops to around 100 degF.

The drawing gives most of the details. The tubing is 3/8" OD refrigeration type. The length of the tubing used for the coil is perhaps a bit too long, but, I'm blessed with pretty high water pressure at the tap, hence the extra length doesn't hurt (wide open, the flow is about 2 GPM). The coils are spot-soldered to the riser tube and a support 1/4" dia. copper tubing support (Hint: use a twist of copper wire to temporally secure the support to each coil and remove them after soldering.)made from 1/4" copper tubing located 180 degs. The end of the 1/4" dia. support was flattened and bent to fit the surface of the bottom coil then soldered to it. A small drain hole was made in the bottom of is tube.

During the boil, the chiller and lid are NOT installed in the boiler! About 10 minutes before I terminate the boil, I remove the stirrer assembly, install the chiller/lid, then put the stirrer assembly back on top. The lid is raised about 1/4" with some wood blocks to minimize the chance of boil-over. A couple of minutes prior to "flame-out", the power to the heaters is throttled, the blocks removed and the lid is secured to the boiler.

The sight gauge is calibrated by filling the pail with water from a 2 quart container. (Hint- mark the PEX sight gauge by scoring with a knife then applying and quickly rubbing off a permanent marker.) Although not shown on the drawing, there's another, electronic type level transducer which will be hooked to a control computer in the future. The level transducer is detailed here.