The Heater Section.

I found a 220v 600 Watt element from a travel kettle. I saw 4" pumps tended to be around this wattage so I'm hoping it s enough for my homebrew version. The good thing about this element is that it came encased in a lump of aluminium. This allowed a good surface contact between the heater and the bottom of my pump.


Unfortunately, when I soldered the base on to the barrel of the pump it domed very slightly. So the flat heater and the base didn't touch as much as they could. So I decided the best thing to do was grind them against each other.
I had some carbide grits so I used them. I did 80, then 220, then 400 and then Brasso. It took and hour or so. I was quite happy with the result. Not perfect but pretty close.

I needed to isolate the element from its metal box, electrically and thermally. I had kept a few blown plug fuses, thinking they might come in handy some day. Ceramic tubing!
I cut the ends off then emptied out the sand.The underside of the element had a three M3 tapped holes in a nice equilateral triangle. So I measured that and marked it on to the metal box. I drilled that out and put an M3 nut and bolt through the holes.(they were proud about 10mm, just enough to hold the fuses)

I put a bit of high temp silicone on to the end of the bolts and stuck the ceramic tube on.

I screwed short pieces of M3 threaded bar in to the underside of the element and these sat neatly into the tops of the fuses!
As this was going to be squeezed against the underside of the pump, I didn't fix it in permanently.

I had a nice ceramic connector and some high temp wire, from an old halogen security light. So I got the power out of the metal box where it could be connected without fear of melting.