Need replacement therostat for Lyman Mag 20 furnace

[CENTEX BILL]

After I retired last year I was given an old Lyman Mag 20 furnace. It was out of an estate and had not been used in 20 years.

In attempting to get the unit functional, I discovered that the thermostat knob would not turn and was frozen. By applying some effort and WD40 I was able to budge the knob enough for the indicator light to come on momentarily. I then thought I could get more leverage if I removed the plastic knob and tried to turn the shaft with a vicegrip. Bad move. The shaft would not move and quickly became bent.

I called Lyman to buy a replacement thermostat and was told I would have to ship the furnace back to Lyman for an estimate of repair. I can only imagine that the repair cost would not be cheap.

Does anyone have any ideas of vendors that could have a workable replacement thermostat that would work that my electrician friend could install locally. I did previously buy a PID unit from a board member in anticipation of using this unit.

I appreciate your input.

Thanks,

Bill

[tryNto]

Bypass the Thermostat and use that PID

[bhn22]

Lymans thermostat is $50.00, plus labor, and shipping both ways. It was made by Robertshaw, but I can't make out a part number for it. I searched the internet and couldn't find a replacement. It may be possible to find a replacement from a kiln manufacturer or something, it should top out around 850-900 degrees. I got so frustrated dealing with Lyman that I built a PID to replace my Mag20s mechanical unit. It sounds intimidating when you first think about it, but PIDs turned out to be easy to build, mine was built in the metal box from a scrapped computer power unit. Here's a couple of pics. I primarily ladle cast, so I used the button type thermocouple, and installed it through a hole in the bottom of the pot to keep the top of the pot clutter free. I removed the Lyman temp control and plugged the hole. There are a couple of vendors here who offer complete PIDs for around $100.00 plus shipping. Mine cost around $60.00 to build, but they can be built a little cheaper, I wanted some features that cost extra, like the plug-in thermocouple. They can also be more expensive too, depending on how great you want it.
Attachment 136349Attachment 136350Attachment 136351

[10x]

Bypass the Thermostat and use that PID

Understated.

[CENTEX BILL]

At the risk of being called stupid, how would I use the PID to bypass the thermostat. Please give me some guidance here.
Thanks,

Bill

[10x]

At the risk of being called stupid, how would I use the PID to bypass the thermostat. Please give me some guidance here.
Thanks,

Bill

First way - the thermostat is removed completely and wires connected directly.
The Pot would be plugged into a 110 outlet controlled by the PID that measures alloy temp with a K thermocouple

Second way
The thermostat would be replaced by the solid state relay. The PID unit would measure alloy temperature using a K thermocouple and send a signal to the SSR (Solid State relay to either pass or turn off power to the pot element.

[Fluxed]

I recommend the PID also.
Its a perfect solution.

[jsizemore]

The first way 10x describes is how my PID is set up so I can plug any pot into the outlet controlled by the PID and the thermocouple is stuck into the alloy in the pot to control the PID. I just max out the thermostat setting on whatever pot I'm using. Simple.

[wv109323]

Definitely use the PID. My Lyman Mag 20 had continuous problems with the wire terminals becoming loose and heating. The "board" that holds the male prongs for the cord burnt up three times.
The circuitry for the PID uses a Solid State Relay. The Relay is "turned on" ,allowing Power to the pot heating element, by a small amount of current from the PID. The PID "looks" at the temperature of the lead in the pot from ( or through) a thermocouple. When the lead temperature falls below your programmed temperature ( i.e. 725* F) the PID switches on the SSR on and the element heats the lead. When programmed Temp. is obtained the PID switches the heating element off. Lead Temperature is maintained + or - 10*F. That is a lot closer than the mechanical thermostat can maintain.
There is only two wires that hook to the heating element that are exposed to the hot temperatures.

[bhn22]

Because of it's age, I made a couple of changes to my Mag-20 to make it more what I wanted. I removed the thermostat completely, and wired a new appliance cord directly to the positive and negative ends of the heating element. I also wired in a new indicator light to help me keep track of power going to the pot. While I had it apart, I bead blasted the pot and used paint stripper to remove the rubberized paint on the tinwork itself. It was a good thing I did, because the tin was rusting in areas under the paint. I bead blasted the tinwork inside and out and painted with "hammertone" paint, which was supposed to be black, but it actually a charcoal gray. I reinstalled the common ground wire, the insulation, and buttoned everything back up. My PID has a single electrical plug on it for whatever appliance it is going to control. I can still plug the pot into the wall, but it has no thermostatic control, so it would just keep heating until it melts down. You can see that my thermocouple is mounted in the bottom of the pot in my earlier pics. My particular setup is holding temps almost dead on. It is a serious improvement to the way the pot originally performed.

[edadmartin]

Id be interested in an auto tune plug n play unit since im tech challenged,send me info and price pm.id need to use paypal too.let me know!

[JonB_in_Glencoe]

Id be interested in an auto tune plug n play unit since im tech challenged,send me info and price pm.id need to use paypal too.let me know!

you could look at OBIII's vendor page
http://castboolits.gunloads.com/show...56#post3522456