Diy heat treat oven help

T

Tom Zaccagnini

Joined
Dec 13, 2020
Messages
29
Hello All,

Fairly new to knife making and I built a Heat treat oven, The build went well but when it came time to fire it up it took 5 hours to get to 1800f. I am at my wits end all my calculations say i should have plenty of power.
Here are my specs
K23 bricks covered the outside with 2" of rock wool board
chamber size 5"x5"x18" = .26 cu feet
120 volts(actually 122 volts measured at the wall outlet)
13ga kanthal wire @ 6.8 ohms (bought the coil from krueger ceramics)
ink bird pid with 40amp ssr
That should be 2,118 watts or 8,144 watts per cu foot
What am I missing?
Thanks in advance for any help or insight
Regards TZ
 
Tom Zaccagnini said:
Hello All,

Fairly new to knife making and I built a Heat treat oven, The build went well but when it came time to fire it up it took 5 hours to get to 1800f. I am at my wits end all my calculations say i should have plenty of power.
Here are my specs
K23 bricks covered the outside with 2" of rock wool board
chamber size 5"x5"x18" = .26 cu feet
120 volts(actually 122 volts measured at the wall outlet)
13ga kanthal wire @ 6.8 ohms (bought the coil from krueger ceramics)
ink bird pid with 40amp ssr
That should be 2,118 watts or 8,144 watts per cu foot
What am I missing?
Thanks in advance for any help or insight
Regards TZ
Click to expand...
Try with direct power to element , use PID just for temperature measurement and see what would happen ?
 
I have the oven running now with the element wired directly to the power
15min 1020f
30min 1195f
45min 1335
60min 1430f
I also put a second tc in the oven on the floor temps were close
 
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This is aluminium foil on rock wool , right ? I would install it with Al foil from inside ............And be careful with that AL foil that close to elements .......Al conduct electricity .


eelEOj8.jpg


Why did you leave that empty space between bricks and rock wool ?
Well , seems it is not empty ......small resolution picture deceived my eyes :D

MKh93xJ.jpg
 
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no empty space, that is steel angle frame around the firebrick, the rock wool was added after my first heat test, trying to insulate and get time to temp down. It helped a little bit, but still painfully slow, and it really starts to slow down after 1500
1hr 15min 1515f
1hr 30 min 1585f
1hr 45min 1645f
does this heat curve seem normal?
how many watts do I need?

Thanks
 
Last edited:
Hey Drew,
I have not measured voltage between coil and relay, I will try that tomorrow after this test and I rewire the pid back in the loop
I am considering bumping up to a 220v system but having trouble finding a coil that will fit, my total stretched coil length is 74"

Thanks all for your help
 
Hi, couple questions, one, what PID are you using so I can look up the specs, two, what was the ordered length of the kanthal wire? When designing heat treat ovens I don't try to figure out everything myself I just head over to Evenheat and look at the specs they use; they're experts so I trust their specs of wattage to volume.

Their knife oven around your specs has a wattage of 1560W 120VAC. So you're higher than their model. For my knife oven I have an Evenheat KO18 at 3120W 240VAC and my notes say 40 minutes to heat up to 1575F.

I just ordered some wire from Krueger Ceramics as well. Hopefully it'll come soon.
 
Try running the PID on auto tune. Mine sometimes takes a while to heat up. I flip to AT and then the heats very fast. Hold the set button until you get to the menu items. Go to OP and change from PID to AT.

Also, did you it set on k type thermo couple. I'm assuming you using k type.

Finally, make sure you aren't in Celsius.
 
cartierusm said:
Hi, couple questions, one, what PID are you using so I can look up the specs, two, what was the ordered length of the kanthal wire? When designing heat treat ovens I don't try to figure out everything myself I just head over to Evenheat and look at the specs they use; they're experts so I trust their specs of wattage to volume.

Their knife oven around your specs has a wattage of 1560W 120VAC. So you're higher than their model. For my knife oven I have an Evenheat KO18 at 3120W 240VAC and my notes say 40 minutes to heat up to 1575F.

I just ordered some wire from Krueger Ceramics as well. Hopefully it'll come soon.
Click to expand...

Pid is ink bird ITC 106vh
the coil I ordered was 13 ga 16 amp 7.5 ohms rated at 1920 watts it was 27"unstretched , I cut it down to 6.5 ohms and stretched to 74"
 
scott kozub said:
Try running the PID on auto tune. Mine sometimes takes a while to heat up. I flip to AT and then the heats very fast. Hold the set button until you get to the menu items. Go to OP and change from PID to AT.

Also, did you it set on k type thermo couple. I'm assuming you using k type.

Finally, make sure you aren't in Celsius.
Click to expand...
for this test I have bypass the pid and running the coil wired directly to the a/c power
yes type k tc and yes set to f
I also cowitnessed with a second tc on the oven floor temps were very close.
 
Seems like a basic PID so the manual should indicate if you have the settings correct. I'll try to find a manual and read through it later if you're still having trouble. For now you have the SSR hooked up the correct outputs on the PID, right? I should have separate SSR contacts on the back. And the SSR is wired correctly? One side is control and one feeds the heating element.

I always use https://www.auberins.com/ for my PIDs. I just bought the N1050, but after talking with their tech support I could have gone with SYL-23X2P. Didn't need the timer aspect as it's a separate from the timers used for ramp/soak, it's purely for turn on for 1 hour and so forth not using the ramp/soak, but I can program it on my regular computer. The SYL-23X2P and N1050 is great becasue it acts like a regular Evenheat controlller. I can control how fast it heats up, ramp, or full blast and then have it hold a certain temp for a time and then turn off.

For the wire I wanted to know the length you ordered, not the coil length, but the number of feet you ordered.

Also, I just ordered the exact same wire and there is no voltage rating on their website, for 13ga wire I'm assuming it was for 240VAC. So you might be able to use it with 240VAC and not change anything. I was going to do the math for you wattage, voltage, resistance, but I can't right now. I just ate my holiday dinner, had a Montecristo Cuban and my head is not there right now. Where did you get that the wire you ordered was for 120V? I'm not judging I'm concerned if I ordered the correct wire LOL.
 
The coil I ordered was a premade coil, the specs where on the site . I did not want to wind my own coil for my first oven so I thought I would leave that up to experts
now I might have to wind my own so I can make a coil that will heat up in a reasonable amount of time
I had to shut down the oven for the night 2hr 30 min to reach 1800f the last 15min rising 50 degrees, would have taken at least another hour to reach my target temp of 1975f.
Oh well there is always tomorrow

Thanks again for all your help
Merry Christmas
 
Tom Zaccagnini said:
the coil I ordered was 13 ga 16 amp 7.5 ohms rated at 1920 watts it was 27"unstretched , I cut it down to 6.5 ohms and stretched to 74"
Click to expand...

Tom Zaccagnini said:
13ga kanthal wire @ 6.8 ohms (bought the coil from krueger ceramics)
ink bird pid with 40amp ssr
That should be 2,118 watts or 8,144 watts per cu foot
What am I missing?
Click to expand...
I don t get it ? You shorten element and you get more watts ? What am I missing ?
 
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