I've had several foundry furnaces over the years.
The first was a Dave Gingery "Lil Bertha." (
https://gingerybookstore.com/LilBertha.html) I built it about 35 years ago and probably used it for at least 25 melts. It had an off-on switch and the only way to judge the temperature was to look at the metal. I used a graphite crucible that had a capacity of a little over one cup. It was built to the plans in the book using an light weight castable refractory and gave me good service. I retired it when the element failed. I only used this furnace to melt aluminum.
Then I got a Kerr Electro-melt with a bunch of casting stuff that I bought from a friend leaving the state to live on a sail boat. It had a pyrometer and a mechanical proportional control for temperature. I replaced the controller with a temperature only PID a few years ago so I could set it to automatically come up to the correct temperature. It works well for both aluminum and brass/bronze, but is a bit small. As with all of the electric furnaces, it takes a while to get to temperature.
The next was propane fired. It uses a 20 pound propane tank for the shell and castable refractory for the lining. When I built it about 15 years ago there were two active casting email groups with a lot of conversations about burners. It has a Zoeller modified sidearm burner. A couple of others that were popular were the Mikey, Mongo, and Ron Reil burners. A web search should find information on all of them. Mine uses a MIG tip for a nozzle and I think the only tools required were a drill, a tap, coping saw, and an angle grinder. bit I did buy a flare from Zoeller. I don't use it often as it there are four to five months a year when it is too cold to drag it outside. The photo shows me braving a brisk 20f day. It will hold about a 6" diameter crucible. If I was going to make another I would stick with this design but use castable refractory for the floor and ceramic fiber for the sides and cover.
When I got into investment casting about three years ago I bought a ToAuto 110v 3KG melter via Amazon. It had some quality problems and kept tripping the GFCI breaker. It took several weeks to get it resolved, but TuAuto's customer service was outstanding. After having me do some measurements they sent me a 220v replacement. It worked out of the box, but the element failed in the first couple of melts. They also did a good job of resolving the problem with that one by sending me a new element and inner liner. I was able to repair the first one, so now I have both a 110v and 220v unit. I've used both of them quite a bit, mostly for melting bronze. I've had one element fail after a number of uses and replaced it with an element I wound from Kanthal wire. (VOG/VoGman has a video on making an element and making a burn out oven on Youtube and his web page, including a calculator for wire size and length and instruction on how to make your own coil from Kanthal or nichrome wire.) I think if I were going to do it again I would buy the one with the perforated heat shield as the outer jacket gets pretty hot. there was a problem I had with these that was my fault, I put my ingot mold too close to the front panel and melted the clear plastic cover on the PID. They still work, but are pretty knarley and I have a couple of replacement PIDs on order.
For the ZA-27 zinc alloy I got a SS pan. I got a cheap hot plate and disabled the sensor that cut it off at a maximum for maximum temperature, and used it and one or two propane torches to get to the 700f to 800f needed. Actually, the propane torches are all that was needed.
