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Old 07-15-2002, 09:02 AM
Bryan Harnois
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Steve

one of the things that I've wondered is the size of the chamber in your furnace you have the 100# pot in with elements above the pot....what is its diameter ( and thickness and it is 2800 IFB isn't it ? ), and is it the one you will be upsizing to the big pot

What I'm getting at is how much power requirement is based on the size of the chamber and thus the thermal mass in addition to the pot and glass that needs to be heated...your dimensions would give me a ballpark idea, because if you've sized it to handle the bigger pot then thermal mass isn't quite as big a deal as I've thought...Pete says both your and Jon's furnaces are hefty

If I go to the long elements ( 28 " hot zone ) then you indicate that 2 banks of 2 each with an SCR and transformer will more than do the job up to 325#

If I want to keep the elements totally above the pot line at say 18 " hot zone, then am I correct that 2 banks of 3 elements each with their own SCR and transformer would do the job? ( I'm increasingly concerned about pelletized batch popping and spewing all over the greater surface area presented below the pot line with the longer elements )

also, if that is correct, then could I more immediately power the unit for a 150# pot using one bank of 65 amp SCR to 240 to 60 Volt transformer to 3 elements with 18 inch hot zones...I could design the crown with 6 chimneys for elements and use just 3 for now, plugging the others with dummy bricks

this would allow me to get up and running with the lower power overhead, but able to expand by adding in the second control loop and elements later

again though, I want to be sure that the thermal mass of a chamber sized big enough to eventaully handle a bigger pot isn't going to totally lug down the system on one control loop now

what do you think

I also wonder if there is some way to post on this site somewhere a table of resistance values per unit of length of hot and cold zones of the elements that Jon can supply ( 6/12) and a summary of the calculation process required to come up with sizing Moly elements...I've done this before with Silicone Carbide, its not hard for SiC if you have the tables, but I do not have them for Moly D, and am having to rely on others for that help...what do you think Steve or Jon or Pete, posting this info could expedite discussions about these issues for everyone

Bryan
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