The kiln measured at the plug (not the individual elements) to the wall is now drawing 13.00 amps with the new coils. About 8% higher than the rated specs of the kiln which is a bit concerning but maybe not that crazy since I'm sure there is some margin for error built in to the parts...? I'll see if it can make it to the golden 2150F goal.
Yes 13 amps when kiln is cold. Will measure again at temp, hoping the amp draw goes down rather than up... though as long as the kiln parts can handle the current I've got up to 16 amps to play with on this circuit.
How very interesting, temperature is at 670 F now and the amp draw is 12.60 from the external plug. Seems to be dipping down. It will be very interesting to see what it will be at 2000/2150F. The ramp up time is annoyingly long. I set the program to: 1 segment 99.99 HLD 500 rA 2200F hold temperature I'm not sure about the rA, is that the total number of hours to hold at 2200F? I think the HLD is how many degrees per minute it will rise the temperature? Which I don't think is correct since I started the kiln 1 hr ago and it only went up about 700F now, that should have taken 7 minutes if the HLD was correct. Maybe its 99.99 F per 10 minute rise? Its a bit of a mystery to me. Data so far: 63 F (room temp) is 13.00 amp 670 F pulls 12.60 amps 1,130 F pulls 12.45 amps 1,600 F pulls 12.34 amps 2,000 F pulls 12.34 amps 2,150 F pulls 12.34 amps
My heat treat oven only has 8.7 A FLA. I can only get to 1800°F empty and it takes me almost 50 minutes. The manufacture tag says do not operate above 1850°F. I've never been able to get it that high.
Not yet, 2,000F at the moment. Seems to be increasing slowly still, will see. Seems like it is going up by about 10 F per minute. So I'd estimate 20 to 30 more minutes if its going to get there, maybe longer if its struggling.
Ok well I'm feeling kind of foolish now for a number of reasons here. The kiln is currently at the goal of 2150 F. It was hovering around 2050 F for almost an hour with the new coil and I was scratching my head. Then I thought to myself "hey let me just plug up the gaps around the door where the brick has eroded away and see if the temperature increases." You guessed it. It was just an insulation issue... I'm thinking I could probably go higher in the 2200-2300F range as it is rated if I fully insulated the cracks around the door. I'm pretty annoyed with myself on this one. I think the insulation may have even fixed the original coil temperature issue and would have saved me the stab in the groin. Also, I looked back at old posts of silver casting and the flask burn out temp was 1340 F not 2150 F. I have no idea where I got 2150 from. I'm actually not even sure if I've ever had the kiln up that high before. I must be going mad. See the pics of the bad insulation around the closed door. You can see the eroded firebrick here on the inside of the door. I wonder if I can get some braided insulating rope and use that to keep the heat in around the door since I think if I replace the bricks they will eventually break in the same way again. This shows the floor of the kiln with a nice little 6x6" kiln shelf I bought from the kiln supply place linked before. If anything melts onto the base of the kiln I can just remove this protective shelf and no harm done. Its nice and smooth and harder than the original kiln fire brick flooring material.
In my opinion, even electric kiln needs a pencil sized draft. Much more than that would be efficiency loss.
I think the decrease in current you observed is exactly what you would expect from the published and previously discussed temp/resistance relationship for Kanthal A1.......4-5% increase in resistance ove rthat range.......~.6amp current/power reduction at constant voltage. Best, Kelly
Haha yes a new metal brain would be great. Its interesting that the amperage seems to plateau. I would have thought it kept going down. I'm guessing the coils for kilns are all cut slightly below their posted resistance ratings so at max temperature they draw the rated amperage? I.e. 9.5 ohms to draw 12 amps at max temp but 13 amps on cold startup. I need to find a supplier that will ship a couple feet of 2300 ceramic rope so I can fix the door insulation nicely. They sell them on ebay but in hundreds of feet.
https://www.ebay.com/str/simondstore/Ceramic-Fiber-Rope/_i.html?_storecat=20714731010 https://www.mcmaster.com/ceramic-rope But tadpole seal is what you really want. You can pick any size you want. http://www.equalseal.com/product-p/ttsilrope.htm I use 1/4 thick ceramic fiber paper as high temp gasket and seal everywhere (no molten metal contact). It wears out but is inexpensive and easy to replace. Best, K
I got 3/8" bulb + 7/8" total width tadpole tape. Looks like exactly what I need to seal up this bad boy. I will screw it into the metal/brick around the door. I wonder why they didn't include this kind of seal on the manufactured original. Seems like a bit of an oversight in design if you lose 300 degrees of temperature out the huge ass cracks between the door and body?? Especially since these kilns were crazy expensive when new, not like a 3 dollar seal would break their construction budget. Since I have the kiln fixed up so nicely, I'm considering repainting the thing. But will have to wait on that for covid to end so I can drive back up to CT to access my sand blaster.
Can you shape the door to inset in the furnace section? That's how the door on my little kiln works. No fancy seal and no leaks.
I've started to install the tadpole tape. It arrived and seems pretty easy to work with. I'll post pics tomorrow for you. Setting the bricks in might be one way to do it. But the tape is probably easier since it just involves a few screws through the steel casing.
