Faulty Lee pot?

[Dunkem]

So I'm pretty new to the casting world so forgive me if this has already been covered. I bought my first melting pot, a Lee production pot IV, and finally got to try it out the other day. Turned on 10 I was impressed how quickly it melted down 8lbs of wheel weight ingots sweetened with 2% tin, I reduced the setting to 5 figuring that would be a good starting point. Using a 2 cavity Lyman 429421 mold I was getting good bullets after just a few warm up pours. Soon the bullets were beginning to get frosted so I set the mold down to cool for a min. It was now that I noticed some yellowish orange crust on the lead. Thinking nothing of it I fluxed with sawdust, skimmed, added a few more ingots and a layer of sawdust to protect the surface of the lead. I resumed casting but began getting frosted bullets again after just a few pours so I reduced the setting to 2. Didn't seem to help with the frosting much and the sprues were taking longer and longer to solidify. Then I noticed the yellow orange crust was back in spite of my protective sawdust coating. Skimmed again, few ingots, and more sawdust and was back to casting. After about 10 mins I noticed the strange crust returning and mold getting to hot again so I decided to call it a day. Skimmed the crud, and shut the pot down leaving it half full. I decided to do some research and from what I can tell, the strange dross was dreaded lead oxide caused by overheating the alloy. I was then curious to test my equipment. I removed the "thermostat" assembly and tested the resistance through it with a multi tester, there was no change regardless of knob position. I then reattached the wires and carefully tested voltage going to the coil while the pot was ruining. Again no change in voltage regardless of the setting. After reassembling the pot I plugged it in and turned it down as far as it can go and it melted the half pot of alloy in about 8 minutes. What y'all think? I'm no electrician but it sounds to me like the knob is stuck wide open. Anybody have a similar experience?

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[Mike W1]

I'm not sharp enough on those things to explain it very well. But it's a thermostat not a rheostat. It doesn't change resistance when you turn the knob. When the temperature changes it opens the circuit. Now it very well may be stuck but you'd have to observe the thing visually. Hopefully someone more versed will hop on here and help.

[Walks]

Still got the receipt? Call Lee.

[country gent]

It may be a stock thermostat or misadjusted and running hot. I would call Lee and see what they have to say. Another option is pick up a thermometer and see what its doing this will tell you if its maintain temp or constantly raising. If your casting area is quiet you can here it cycle on and off usually also. I believe if you remove the knob the is a adjustment screw in the shaft to fine tune it. But if its stuck open fine tuning wont help.

[jimkim]

Call Lee, tell them what it's doing. It sounds like a faulty thermostat to me.

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[hunter74]

I've had 2 Lee pots and both of them had a bad "thermostat". That bimetal #&ap does not work righ! I've got mine PID adjusted and then it works ok

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[Dunkem]

Thanks for the input everybody. I'm going to call them today and explain my situation. I was casting outside in a slight breeze, maybe that is enough to cool the thermostat and keep it on. I could hear it running, it did change pitch occasionally, but never went completely silent until I unplugged it. I am going to build myself a PID eventually but decided to devote my casting budget to expanding my mold collection for the time being.

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[Dunkem]

Quick update: called Lee and spoke to the tech. He confirmed that the control is indeed a thermostat, not rheostat as I originally thought. He wanted me to make sure it wasn't functioning before sending it back and told me it needed to be tested under heat. I disassembled the unit and held a heat gun to the thermostat and could see the contacts separating. I then partially reassembled the pot plugged it in and tested voltage at the coil connections while applying heat with the heat gun (harder said than done). Sure enough it works as designed. I suspect that it may be the cooler weather and breeze I was casting in keeping the thermostat too cool to function correctly. The tech also mentioned that he and others he knows will hook the pot up to a dimmer switch to give more control over heat. Anybody ever try this? If so to what effect?

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[jimkim]

There are other thermosts out there. Maybe you could get one like they used on the old Lyman ans SAECO furnaces.

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[Mal Paso]

The Lee Control is not a thermostat. It is an "Infinite Control" just like an electric range top. Heat is applied to a bimetal spring. When the spring reaches a certain temperature it flexes and opens a pair of contacts cutting power to the spring heater and the pot heater. When the spring cools the contacts close turning on both heaters and the cycle starts again. The Control Knob pushes against the spring changing the amount of time the heaters are on. Some of the heat from the pot does affect the Control but not enough to call it a thermostat.

I think your control may be out of spec. With the knob set low the element should be off most of the time regardless of the pot temperature.

A thermometer would help as the numbers on the control do not represent a temperature and the amount of heat required changes as the pot empties.

As a former Lee owner I would recommend a PID control. It covers thermometer and control in 1 package. Lots of info here.

[Walter Laich]

as Mal said above ^ a PID would solve your problem as well as add a marked increase in accuracy. My pot will hold to within 1° as I cast.

I would also suggest a lid of some type to hold in the heat in the pot. No need to let it dissipate into the air--keep it in the pot where it needs to be

[HangFireW8]

I have an old Lee 10 lb pot I hardly use any more. When it would no longer melt lead I put a new heating coil and control on it. Then it would barely melt lead. So I bent the control around until it did. Then my Mag25 was sorted out and I haven't used it since.

A plugin pid would not have helped because even on 10 it cycled off too much. A PID that bypassed the controller would have worked.

[Grmps]

You are right about surrounding temperatures affecting the thermostat. This is also an issue with convection and toaster ovens for baking PC and HT. +1 on a PID, never looked back

[bkbville]

The tech also mentioned that he and others he knows will hook the pot up to a dimmer switch to give more control over heat. Anybody ever try this? If so to what effect?


You'd need a 600W dimmer, but I don't see how you'll benefit, as you would still have open loop temperature control. A PID (closed loop control) is a better way to maintain and control temperature.

Using a PID I would simply bypass the thermostat - jumper it right out of the power circuit - but then, only use it with the PID.

[Dunkem]

So with the weather warming up and a less windy day I tried again. I also did my best to shield the pot from what little breeze there was whilst maintaining adequate circulation. Wouldn't you know it, it worked like a charm. I found that a setting of 4 gave the best results. I could also hear the element cycling on and off at a steady rate. I also skimmed the sawdust off the melt after it had done it's job rather than leaving it to protect the surface of the alloy. This seemed to remedy the orange-ish dross i was getting last time. The sawdust was acquired from my local home improvement warehouse and probably consists of mostly particle board, so I wonder if it was some glues/resins that was responsible for the crud I was mistaking for lead oxide. A PID is definitely on my wish list in the future, but for now I think I'm satisfied learning how to control my temp the old fashioned way. Thanks again all for your input. Its nice to have this pool of knowledge willing and available to help beginners like myself.

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[stubshaft]

Yesterday I pulled out an OLD (35 years) 10# LEE pot. It sat for over 35 minutes and just barely melted a load of pure. Rather than toss it I'll order a new element and thermostat from LEE for around $25.00.

[Messy bear]

Hey guys! These Lee pots don't have a thermostat. Think about it. How does heat in the pot "transfer" across an open air gap to the bimetallic switch and do any regulating at all? It's just a cheap easy design that doesn't regulate. Put a good thermometer in it and watch it climb. 800 plus degrees is not unusual for these junkers! You have to regulate it by adding lead or turning on and off. Or PID as mentioned already. Junk! ( I have one but don't like it)

[Messy bear]

Also congrats to Dunkem for being smart enough to smell a rat with that pot so he doesn't have to smell all those lead fumes when these things overheat! Dangerous pots!

[stubshaft]

Yesterday I pulled out an OLD (35 years) 10# LEE pot. It sat for over 35 minutes and just barely melted a load of pure. Rather than toss it I'll order a new element and thermostat from LEE for around $25.00.

Update: I called LEE and they will send the thermostat and heating element for FREE. I just pay shipping.

[Echo]

I'm not sharp enough on those things to explain it very well. But it's a thermostat not a rheostat. It doesn't change resistance when you turn the knob. When the temperature changes it opens the circuit. Now it very well may be stuck but you'd have to observe the thing visually. Hopefully someone more versed will hop on here and help.
And it's not a thermostat, it's a control. It controls the power going to the element, with no feedback from the element, so it is not a thermostat, which has a feedback loop. There is a bimetal strip involved that heats up according to the power going through it. The knob controls the amount of pressure applied to the bimetal strip - more pressure, power goes through the strip longer to warm it up to make it spring away from the other contact, increasing the heat applied to the melt.