Project - PID on Lee Pro 4 20 furnace

[popper]

Small aubrin unit with 1000 K probe. Works great for the Lee pot and doesn't take up much room on the bench. Neither HS or SSR(only a 15 amp unit) get warm at all, HS grease on the SSR and the HS. Sorry for the bad focus, but you can see how I put it together. Yea, I have to put strain relief and put the back plate on, get rid of the tape holding it together, sometime.

[bosterr]

I just finished my first casting session with my new PID. I was using my 400 gr. 50 cal. 2 cavity mold (Mountain Molds magnum sized aluminum block) and a Lee 440 gr. 50. cal 2 cavity. I set the PID at 750 degrees figuring the Mountain mold would need that much heat. It wasn't able to reach that temp with my 20+ year old Lyman Mag 20 bottom pour. I pre-heated the molds, although they could have started out hotter. After an entire potfull reject rate was about 50% with the Mountain and about 25% with the Lee. The rejects weren't filled out quite sharp enough. I added a little bar tin, about an inch off a 3/4 in square bar. I read a lot of you guys said the PID will learn the pot, which was the case when I tried it out at 650 degrees with a 2/3rds full pot last week. It wasn't until a good hour or more into the casting session that the pot achieved the set temp. Most of the time it stayed about 725 degrees however. What temp would you say would be the optimum for this big aluminum mold?

BTW I have an aluminum PID box that I got from Auberins that I thought would be too much of a challenge for me to fit everything into it. If anyone is interested in buying it, let me know.

I want to thank Walter and BigJason for their help with the PID.

[Mal Paso]

Is the Thermostat still connected on the lyman? That could be your upper limit.

[bosterr]

Yep, I set the pot at it's highest setting and is plugged into the PID. I must say, it did reach 750 a few times. Should I just let the potfull rest and not start casting for a while? Maybe to let it get to set temp and stabilize for a while?

[Ausglock]

Sorry If this has been covered (I couldn't find any reference)
How do you set it for Degrees F rather than Degrees C?

Thanks.

[bosterr]

Ausglock... Did you get your PID from Auberins? I had been having trouble with mine and contacted customer service there. I went through all the parameter setting shown on page 3/8 and re-set all of them, then it was already on farenheiht. The instructions for changing to F is on page5/8 paragraph 4.14 If that dosen't do it, call Suyi at Auberins.

[Frozone]

Yep, I set the pot at it's highest setting and is plugged into the PID. I must say, it did reach 750 a few times. Should I just let the potfull rest and not start casting for a while? Maybe to let it get to set temp and stabilize for a while?

I'm not sure just how hot a Lyman pot can get, but I would think it would go past 750 under full power.

One option is to add a toggle switch (SPDT) that will remove the thermostat.

As a test, I'd wire around the thermostat and see if it reaches and holds temp better.

Your PID will automatically adjust for the pot (< +- 1 degree) but it will take a little time - 30 minutes or so about average. It will do a fair job before that time however (+- 10 degree) unless the thermostat is interfering with it's operation.

The PID also has to relearn every time you adjust the temperature as well, and this is most notable if the heating element is marginal for the job.

[bosterr]

Thanks for the info, Frozone. I took today off work and sat for 6 1/2 hours and made 140 pounds of boolits. I ran the temp at 670 degrees because I was using 3 Saeco 4 cavity molds and it worked like a dream. I never saw more uniformity than I did today, and I've been casting since the 70's. I know aluminum molds need more heat than iron so I guess I have to be patient and let the temp get up there, no matter how long that takes. If it won't hold at 750 degrees, I'll try your suggestion. Thanks.

[Mal Paso]

Yep, I set the pot at it's highest setting and is plugged into the PID. I must say, it did reach 750 a few times. Should I just let the potfull rest and not start casting for a while? Maybe to let it get to set temp and stabilize for a while?

What Frozone said. Wire out the thermostat and see. If the thermostat has 2 connections a wire between them will work.

The Lyman Thermostat has a range and I'll bet 750 is the upper limit of that range.

Now that you have the PID you may not be interested but many of the older thermostats can be opened up and tweeked to get a higher setting. The control knob modifies hydraulic pressure from the capillary tube on a micro switch.

[bosterr]

I didn't open up my Lyman pot yet. Do you mean I could wire on an extension cord plug in and eliminate the thermostat?

[Mal Paso]

Unfortunately there isn't a way to bridge the thermostat without opening up the part of the furnace that houses the thermostat.

Remove the Thermostat Knob and see if there is a hole in the end of the shaft with a tiny slotted screw. Turning that clockwise should raise the temperature but go slow and see what happens when you give it a half turn.

If not I or someone here could walk you through the electrical. If it's a 120 pot there should be only 2 connections to the thermostat and be quite simple. 240 usually has 4 connections as both wires to the heating element are disconnected.

[bosterr]

Hello MelPaso...

This week I attempted to cast again with the 2 cavity 50 cal. alum mould. This was made by Mountain Moulds and the physical size of the block is rather large. I attempted to try it again this week with the PID set at 750 but the pot still wanted to control itself. The pot did reach 750 for just a short time, and even 780 for a few seconds. I loaned this mould to my friend who uses a Lee 4-20 set on "8". I also loaned him my PID so he could find out and tell me what temp this big mould required. It turned out that "8" was 880 degrees, and that's the temp that the mould required. Obviously my Lyman can't reach this. I removed the housing and exposed the thermostat and found there is no set screw to adjust it, just 2 white wires attached to one side of it that are wrapped in fiberglass tape. So, if you could spare the time, could you tell me how to eliminate the thermostat? I know I will not be able to just plug it into a recepticle any more, only into the PID, but do you think it's possible to burn up the heating element if run at such elevated temps?

[Frozone]

Just connect the 2 wires from the thermostat to each other. Make sure they are insulated from the case (wrap em in electrical tape).

OR you could bridge the two wires with a switch. That way you can select what happens. Close the switch to cut the thermostat out, open it and you have the original pot..
You could still use the thermostat if you wanted to Not use your PID.

[Mal Paso]

Frozone has it. If there are only 2 wires attached to the thermostat, connecting them will bypass the thermostat.

The element should be ok at that temp but preheating your mold on a hotplate ( if you aren't already ) might let you bring that lead temperature down.

[Alchemist]

I'm starting to put my PID controller together, and while doing a little research I found the following table that may be helpful for others who are curious about the capacity of their wiring.

http://www.powerstream.com/Wire_Size.htm

The reason I looked it up was that I'm gutting an old computer power supply to utilize the case. I was checking to see if the existing wires from the power cord jack would be sufficient. The power cord and internal wiring are 18 AWG, which I thought might be too light. So here are my findings as I understand it. (Please point out any mistakes or miscalculations on my part)

I'll be plugging my RCBS Pro-melt into this guy, it is rated at 800 watts. Power divided by voltage gives you the current, so I used 1KW divided by 120 = 8.3 amps. According to the above table, 18 AWG max amps for chassis wiring is 16A, so I would still have a 100% safety margin.

Have I committed any blunders here?

[Frozone]

You'll notice the 2 columns in that chart, one for chassis and one for transmission.

The acceptable maximum amperage is dependent on distance.
A short (say 1") run of 18g wire will pass a lot of current for a short while.
It's kinda like a slowblow fuse!

I consider 10A for 3 ft an absolute max for 18g and would prefer 8A max.
The more intermittent the load the better.
As long as you stay under 1000 watts and under 3 ft., 18g works fine.

If you search a little more you'll find a bunch of those charts - they are all different!!!!!

[Alchemist]

Thanks Frozone

Would I be wise to junk the 18 AWG and just rewire the whole thing with 16 AWG? I'll be operating the PID, the end load (Pro-melt) and a transformer to power the original 12 VDC chassis fan.

[Frozone]

I'm a big fan of overdesign.

I'll go out on a limb here, without knowing exactly what you have planned.

If you can get it, use a 16g power cord, otherwise 18g will work. If you use 18g keep it rather short < 4 ft.
I used 18g power cord in my first design for a LEE 4-20 (~710 watts), it gets a little warm while the pot heats up but it's fine after that.

Bring that 16/18g (through a fuse and/or switch) to a terminal block. Then continue to the SSR(/relay/output) with the same 16/18g.
You can use 20g or even 22g to the PID and the fan.

[Alchemist]

After checking into what I have a little further, I've discovered that the input AC jack for the power supply chassis is only rated for 5 Amps. So I'll be stripping out all the original parts but the power switch (15 Amp) and the cooling fan. I'll also be replacing the wiring with 14 AWG. I also believe it's better to overbuild, which is what led me to check current ratings of the existing wiring. It would have probably worked (at least for a while) but I want to avoid premature failure from overheating.

Once the smoke gets out of an electronic component, it's pretty well done for!

Thanks for the input and great ideas fellas...

[boltons75]

I have my components on the way for my controller. Should have my pid and ssr tomorrow. Then the fun starts, I plan on using it for both my lead pot and lube sizer heater.

Always carry, never tell.