STEP 5: Secure the heating element
To seal the kettle from the outside, we use the same trick that Blichmann uses on these kettles to seal all of their weldless fittings: A high temperature food grade silicone o-ring is placed inside a metal shim/washer to make the seal. The washer ensures that we don't overly compress the o-ring and cause it to bulge and leak when we tighten the large nut inside the kettle. It also ensures that there's a tight fit between the electrical box and the kettle: Without the washer the box would be resting against the o-ring and would move around if it were pushed/pulled. The black rubber washer that was included with the heating element is not used.
Just like Blichmann's weldless fittings, the size of the o-ring and washer were selected so that you'll be able to tighten everything down completely and the electrical box won't move at all.
Remove the rubber washer and then carefully feed the heating element through the hole in the conduit box. Place the high temperature silicone o-ring (1-3/16" ID x 1-7/16" OD x 1/8" width, AS568A Dash No. 217) and 18-8 stainless steel washer (0.075" thick, 1-1/2" ID, 2-1/4" OD) around the element threads:
Carefully feed the heating element through the hole in the kettle:
Screw on and tighten the 1" NPS stainless steel lock nut on the inside of the kettle using a regular 2" wrench while using a water heater element wrench on the outside to stop it from turning. Tighten this down until the box on the outside is completely tight:
The outlet box on the outside should now be pressed up against the kettle and unable to move or spin. The washer between the box and the kettle ensures that the o-ring did not bulge or get overly compressed. While it looks like there may be 2-3 washers in the photo below, there's actually only one. You're seeing reflections off the box cover and the kettle:
A cut-away view of how it all works:
The high temperature food-grade silicone o-ring creates the waterproof seal between the kettle and the electrical box in the same way that Blichmann does with their weldless attachments (sight gauge, thermometer, and 1/2" valve) on their Boilermaker kettles. The black rubber washer that was included with the heating element is not used.
When compressed slightly after installation, the o-ring presses against the heating element to seal off the inside of the kettle from the inside of the electrical box. The last thing we want is hot liquid from the kettle to seep into the outlet box. To test this lateral seal, we boiled ~10 gallons of water for about an hour with the outside electrical box cover removed. No matter how we pushed, pulled, or tried to turn the electrical box, we were unable to create any leaks.