Kettle rebuild

[DEMPSEY]

OK,after leaving this abandoned for nearly 2 years,I am finally going to finish it. IT will be provided by many but the other stuff I am going to do. Not happy with my cooker elements under my kettle,I got a 3 kw element from will_D 2.5m long and you bend it to the shape you want. Using a keg I got from a UK source  ,a few years ago,this is where I am at.   

[DEMPSEY]

next I cut a second base from the other bashed  UK keg and placed it on top to help press it down.

[DEMPSEY]

Next  ,I used timber wedges to secure it in place.

[DEMPSEY]

To keep the heat in and not roasting the floor I planned to fill the base with a fire clay so I used 12mm plywood and some 2mm pvc sheet to create a well to pour in the fire clay.

[DEMPSEY]

having fitted the well I fitted a single electrical box to allow the ends of the element in to and to wire it up.

[DEMPSEY]

Wired it up with a 3 core cable and earth wire to the keg wall.

[DEMPSEY]

earth wire to keg

[DEMPSEY]

Filled up the cavity with a mixture of sand/cement and bonding. Recommended by a fireplace installer.

[DEMPSEY]

My first test was a partial success,after a few hours I had a failure. Did not account for the timber wedges burning and so caused alot of smoke as they burned. Also the wiring did not stand up to the heat. Stripped it to clear all the burned timber.

[DEMPSEY]

and here

[DEMPSEY]

here is the burnt wiring

[JD]

Hi Dempsey,

I really wish you well with this but I'm not confident that it will end well. The elements below the keg floor, I fear, will burn out before very long. The problem, as I see it, is two fold: first, the elements are not making a good enough contact with the floor: only a millimetre or two of the element cross section is in contact with the keg floor, while maybe twenty millimetres is contacting fresh air. Yes, heat rises, but that's convection, and elements transfer heat best by conduction. Second, stainless steel is a lousy conductor of heat. It's not for nothing that most SS cookware has an aluminium base to ensure heat is evenly distributed.

I'd suggest putting the elements inside the keg. That way the element's surface contact is total and the heat goes straight into the wort without significant loss.

/J

[Will_D]

The elements below the keg floor, I fear, will burn out before very long. The problem, as I see it, is two fold: first, the elements are not making a good enough contact with the floor: only a millimetre or two of the element cross section is in contact with the keg floor, while maybe twenty millimetres is contacting fresh air. Yes, heat rises, but that's convection, and elements transfer heat best by conduction. Second, stainless steel is a lousy conductor of heat. It's not for nothing that most SS cookware has an aluminium base to ensure heat is evenly distributed.

These elements are a low density design that can be used in air. They can be immersed but don't have to be!

Anyways time will tell. Its Dempseys design and he doesn't want the elements inside.

Have you seen the underside of a Burco boiler There the element is also bonded to a 6 " diameter chunk of metal.

Brian just needs to get some high temperature (silicon based ) 1.5 mm2 cable to wire up to it.

[JD]

These elements are a low density design that can be used in air. They can be immersed but don't have to be!

Low density elements still need to transfer their heat. Because the under-keg is an enclosed space, and because the thermal conduction path from element to wort will be so poor, I fear the enclosed space will accumulate a large fraction of the heat produced by the element. The inability of the heat to escape this area quickly enough, I contend, will culminate in a burnout. Let me caveat this by saying that this is just my gut talking. I don't know the exact details of Dempsey's system and his mileage may vary in any case. It is a concern, not a prediction.

I'll be very interested to see how well this succeeds.

Have you seen the underside of a Burco boiler There the element is also bonded to a 6 " diameter chunk of metal.

It is that block of metal, which is a highly thermally conductive aluminium alloy, that ensures the majority of the element's heat is conducted into the Burco base and hence to the water within. Basically, the full circumference of the element cross section is thermally well connected to the vessel contents. 

/J

[Dr Jacoby]

I use one of these bendy elements in my keg. They're great but just one word of caution. I notice that you are using a crimping connector to attach the earth to the keg. I used to do this but the crimp came loose and it was only pure luck that I noticed it prior to brewing one day. It was easy to spot for me because I attached the earth in plain view under the terminals at the side of the keg. I'm super paranoid about the earth now and have made sure it is very well attached and more or less in plain view so I can check it each time. Maybe safety overkill but I'd thought I'd throw it out there anyway. 

Edit: looking at your pictures again I see that the earth connection is on the side of the keg. That's handy for checking the connection at the very least.