Small electric furnace

Normally I just lurk in the background around here. I've wanted to get into metal casting for years but just haven't invested the time or money. I want to get into building model steam engines when I retire in a couple of years, and I figure casting my own parts will save me a bundle. I've been making a half-hearted attempt at collecting bits and pieces for a gas/oil furnace for years, just haven't committed to it yet. Then this little jewel came along.
https://www.ebay.com/itm/165324710861?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2648

Yup, a busted LITTLE electric furnace, 3Kg max. (I think that translates to a little more than 1/2 pound of aluminum.) Normally these things cost around $275-$300, when I saw this one I couldn't resist and bought one. I've been designing and building industrial control systems for over 30 years so this guy not working didn't scare me.

I figured that this thing will consist of a heating element, probably a solid state relay, and a PID controller to be the brains of the outfit. One or more of those items was the problem.

It arrived yesterday, so I just HAD to tear into it last night. The first thing I noticed is that there's not a fuse or a circuit-breaker in this thing - that will be changed in the near future. All of the wiring appears to be of decent size and I believe that it's fiberglass covered for high temperature applications. That's a good thing, but they've got the cheap-a**ed Chinese clone of a Japanese PID controller living in the same space. Apparently it's not going to get hot? Oh well, that's what cooling fans were invented for.

There is a 40A SSR (Solid State Relay) mounted on a hefty heat-sink. The line and load side connections to the relay looked good, and the control side of the SSR said that it needed between 9-32VDC. The 2 wires on the input were connected to the PID controller. I popped the PID controller out to get a better look at the connections and see if by chance they had labeled the connections, somewhere. They were labeled - sort of.

According to the label on the PID those 2 wires were connected to the NC (Normally Closed) contact, AND the NO (Normally Open) contact on a relay. OK - anybody that knows relays can tell you that WON'T work with a relay. Then I got to wondering if maybe they were playing games with those 2 terminals inside the controller that they weren't telling me about - Chinese clone PID controller dontchaknow.

Time for a live-fire demonstration. I plugged it in, and sure enough it didn't work - no red indicator on the SSR telling me it's on. If the input connection to the SSR actually is connected to a relay it makes sense that this thing wouldn't work, those 2 terminals will NEVER be connected to each other and they've got no power source. BUT, that also makes NO sense. There are other units out there that work, they have GOT to be playing games inside the controller with those 2 terminals - time to get out the meter and see what's going on.

I checked those 2 terminals and whaddyaknow, there's 12VDC on them. OK, SSR says it needs 9-32VDC - it SHOULD be on. Only one LITTLE problem, the positive side on the PID controller was hooked up to the negative terminal on the SSR and vice-versa. They had the input polarity to the SSR backwards. OK, unplug everything, flip those 2 wires around, and SHAZAM - I gots heat.

It heated up to temperature, and shut off - so everything is mostly Hunkee-Doree. The biggest problem now is that the PID controller thinks it's 72°C in my basement - I don't think so TIM! Now I've just got to see if my secret decoder ring can make any sense of the 5 page Chinglish manual that I found on-line so I can get the controller's head on straight.

I don't know if this LITTLE beast qualifies me for inclusion in this august community or not, but I'm getting closer.

Don

 

Kelly:

It's a jewelry furnace so it's 3Kg of Gold, think small.

It's like this one, just a different nameplate.
https://www.amazon.com/TOAUTO-Upgraded-Electric-Refining-Precious/dp/B088B8PZVK

And I didn't get all the goodies, I guess they figured they could send them to the next guy. I did get the 3Kg crucible and tongs though. The tongs will get the myfordboy modification to keep them clamped on the crucible.

I think it's either a 60mm or a 76mm OD on the 3Kg crucible. Power, it's 120V so I'm guessing MAYBE it's 1200-1500W? Spec's aren't really these guys forte'.

Don