Could use some advice from those more PID savvy than I.
A few months ago I was given an old Lyman Mag20 furnace. The only thing the person that gave it to me knew about it was that it belonged to a relative that had passed and that it didn't work.
Finally got around to messing with it this week. Thermostat was the problem, multimeter read an open loop when turned on. Cheapest replacement I found is $70. I took thermostat apart to find that one of the tabs the contact arm had come loose from the notch it was supposed to pivot in. After reassembling the thermostat now when I turn it on I get a definitive and satisfying click of contacts well uh... contacting and and my meter confirms the circuit is closed. I still need to do a little temp testing to make sure its working as expected but before I bother...
I'd been planning to build a PID this winter anyway for my other pot so as I was looking at this Mag20's innards strewn about my workbench I thought to myself... Why bother with the thermostat at all and just install a PID in place of the thermostat like a Mag25. The Mag25 looks like a sideways Mag20 even, at least to me. I Google Image searched for a bit but couldn't find any pictures of a disassembled Mag25 but I did find one of the back of one (which would be the side of a Mag20).
Noticeable differences:
- The mag25 has louvers and a fan added for ventilation which I assume is to keep the PID from overheating / melting.
- Noticeably absent behind the Mag25 louvers are the gobs of ceramic fiber insulation that the MAG20 was stuffed full of.
Internally there is more than enough room for the pid, ssr, and an 80mm or 92mm cooling fan and adding additional vents to the back and sides is easy enough.
Not being fully familiar with PIDs just yet. Would it cause the PID to be less accurate? I could reuse some of the ceramic fiber insulation to "wall off" the PIDs ventilated compartment from the heating element and pot. What concerns or precautions are there with installing it into the furnace itself? In other words, why wouldn't someone want a PID installed into the furnace itself?
Thanks