Diy heat treat oven help

Natlek said:
He used K23 bricks covered the outside with 2" of rock wool board , that is MORE then enough isolation for HT oven .
If bricks are really K23 type I don t know what to say .....lack of power ?


That is useless overkill. You can add three foot isolation and that want help more .If you run oven long enough heat will get to surface ,anyway .
My point is we simple can t keep heat inside , heat transfer always occurs from a region of high temperature to another region of lower temperature , it is only matter of time when heat will reach outside surface of oven . Maybe vacuum will slow it more
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I agree after 5 hours of run time things are going to get hot
 
Cushing H. said:
Just catching up. Agreed ... this sounds weird.

scott ... not sure if I agree with your latest. The equation for power is simple: power = voltage squared divided by resistance. 121^2/6.8 = 2154. Diameter or length of wire does not enter into it, except, as you point out, in terms of survivability of the element.

given the pid is bypassed, I would focus on heat loss. Are the bricks really what we think, and are they tightly fit?
I got the bricks from DC care amazon don't know for sure how good they are. I did mortar all seams with refractory mortar

I am wondering about the door? Are the bricks equally thick there? ... and especially, HOW TIGHTLY DOES IT FIT? There is no gasket material present. Do you have any indication of significant leakage of heat through the door gap?
Door is 2.5" thick with 1/2" routed into oven, fit is pretty tight. That being said it is not insulated as well as the rest of the oven and does get hot after a couple hours

the other question might be whether you are really getting the power delivered at the wall socket that you think you are. If the house wiring is old or underrated, you will measure 121V with no load, but that might be dropping when the oven pulls power. Try measuring the voltage at the other open socket while the oven is running...
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I will try to measure voltage at open socket today
Thanks
 
scott kozub said:
I gotta say this is really weird. The oven looks well built and wattage to ft3 is high. This thing should heat up fast.

I recently broke a coil. I tried jumping the break with a piece of stainless. I found it would get to about 1500 degrees and then drop. My guess was that the ss was creating too much resistance at that temperature. I had a small bit of Kenta left over that I jumped it with and its back to normal.

As heat goes up, electrical conductivity goes down and you loose power. With my Diy oven I twisted the wire leads where it comes through the wall and is connected to the power supply. This is to keep the temper down at the leads. This is a wild guess but maybe if the leads aren't twisted they are transferring too much heat at your connections and the resistance is climbing too much. I doubt this is it though.
Lead ends are twisted

I'm not sure what else it could be. Ohms at the leads look good, you bypassed the pid and are measuring in ferenheight and your math is correct. Blocks look fine and you'd feel the heat loss.

Do you have a way to measure the current draw instead of calculating it?
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No I don't have an amp meter, might have to get one. I was looking for one of those Kill a watt thingys that monitor power consumption of your devices
 
PEU said:
The "chalky" K23, Morgan thermal ceramics, are the best IMHO, they weight around 800 grams and feel light, creamy colour. Then you have the white K23, weight about double that and aren't as good. Why? they absorb heat, so it takes way longer to reach temperature, and there is no outside insulation that would help you with this problem.

If it helps in any way, here is my finished WIP, I use it regularly since then: https://www.bladeforums.com/posts/15079540/

Pablo
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Nice build!
 
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I'd pick up a clamp style multimeter just to have as a sanity check, but it may not tell you anything you don't already know, or aren't able to figure out with voltage and resistance readings.

Can you take a picture of your element while it's heating up? What color does it get to? Does it seem "bright"? Here's a picture I took of mine after reaching around 1575, if I'm remembering right:


Again, mine is 220, so I'm sure that makes a little bit of a difference, but wattage is wattage, and 1800W should still get plenty bright.
 
Hubert S. said:
The Killawatt is convenient, but check the amperage first. Mine is rated for 15A only.
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Cushing H. said:
Just catching up. Agreed ... this sounds weird.

scott ... not sure if I agree with your latest. The equation for power is simple: power = voltage squared divided by resistance. 121^2/6.8 = 2154. Diameter or length of wire does not enter into it, except, as you point out, in terms of survivability of the element.

given the pid is bypassed, I would focus on heat loss. Are the bricks really what we think, and are they tightly fit?

I am wondering about the door? Are the bricks equally thick there? ... and especially, HOW TIGHTLY DOES IT FIT? There is no gasket material present. Do you have any indication of significant leakage of heat through the door gap?

the other question might be whether you are really getting the power delivered at the wall socket that you think you are. If the house wiring is old or underrated, you will measure 121V with no load, but that might be dropping when the oven pulls power. Try measuring the voltage at the other open socket while the oven is running...
Click to expand...
Measured voltage at adjacent receptacle with oven running,voltage dropped to 116v
should still put me at 2kwatt
 
Thanks to everyone for all your help.
I am going to order a new coil and rewire for 220v, as Tim Tool Time Taylor would say "needs more power"
will post when I get it up and running
Thanks again TZ
 
Tom Zaccagnini said:
Thanks to everyone for all your help.
I am going to order a new coil and rewire for 220v, as Tim Tool Time Taylor would say "needs more power"
will post when I get it up and running
Thanks again TZ
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Lol. I never really watched the show ... but caught it enough to get the reference. I especially liked the little gas engines he would occasionally mount onto a tool :-)

I must say that this has me a little concerned for when I (finally) get around to building an oven. I only have 115 / 15 amp in my garage. ... so I’ve got to get the heat loss thing right...
 
Cushing H. said:
Lol. I never really watched the show ... but caught it enough to get the reference. I especially liked the little gas engines he would occasionally mount onto a tool :)

I must say that this has me a little concerned for when I (finally) get around to building an oven. I only have 115 / 15 amp in my garage. ... so I’ve got to get the heat loss thing right...
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My advice, buy good bricks turn them on edge for a 4" thick wall, and keep the chamber small
Good luck with your build
TZ
 
Drew Riley said:
I'd pick up a clamp style multimeter just to have as a sanity check, but it may not tell you anything you don't already know, or aren't able to figure out with voltage and resistance readings.

Can you take a picture of your element while it's heating up? What color does it get to? Does it seem "bright"? Here's a picture I took of mine after reaching around 1575, if I'm remembering right:


Again, mine is 220, so I'm sure that makes a little bit of a difference, but wattage is wattage, and 1800W should still get plenty bright.
Click to expand...

your oven looks just like mine
 
Tom Zaccagnini said:
My advice, buy good bricks turn them on edge for a 4" thick wall, and keep the chamber small
Good luck with your build
TZ
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Yeah .... thats what I am thinking. I do need it to be a certain size though .... so will have to revisit the plans. Not sure if I will be doing anything on it until spring anyway (between Covid, Winter, and my utter inexperience with welding......
 
scott kozub said:
I gotta say this is really weird. The oven looks well built and wattage to ft3 is high. This thing should heat up fast.
Click to expand...

Agree ^
My oven has the smaller 2 1/5" bricks and no mortar or any kind of insulation and it will be at temp in 15-20 minutes

??????
 
If you hooked up 110vac directly to coils and it's drawing the amperage it's suppose to I'd have to say it's the wrong bricks. Rewiring for 220vac will only help a little. I disagree with Natlek. INUSULATION is everything. I built and live in a super insulated house! Trust me my energy costs to heat and cool would amaze you. So low they won't put us on a budget. lol BTW my heat treat oven is super insulated too 240vac. Goes to 1975 in 35 minutes and holds it within a degree as long as I want it or need it too. You can put your hand on all five walls that are super insulated while it's at temp and hold there forever. Now the door that's not super insulated beware after it's to temp.
 
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Spalted said:
Agree ^
My oven has the smaller 2 1/5" bricks and no mortar or any kind of insulation and it will be at temp in 15-20 minutes

??????
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can only be two things, power is not as high as I think it is, heat loss is way worse than I think or both
The bricks looked good but I had nothing to compare them to and not much I can do about them now without tearing the whole thing apart and starting over, the power on the other hand I can increase
 
LCoop said:
If you hooked up 110vac directly to coils and it's drawing the amperage it's suppose to I'd have to say it's the wrong bricks. Rewiring for 220vac will only help a little. I disagree with Natlek. INUSULATION is everything. I built and live in a super insulated house! Trust me my energy costs to heat and cool would amaze you. So low they won't put us on a budget. lol BTW my heat treat oven is super insulated too. Goes to 1975 in 35 minutes and holds it within a degree as long as I want it or need it too. You can put your hand on all five walls that are super insulated while it's at temp and hold there forever. Now the door that's not super insulated beware after it's too temp.
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I don't know for sure if it what the amp draw is I do not have a amp meter
I live in Hawaii my energy cost to heat and cool would amaze you ;)
 
Tom Zaccagnini said:
I don't know for sure if it what the amp draw is I do not have a amp meter
I live in Hawaii my energy cost to heat and cool would amaze you ;)
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12degrees F here now. Furnace hasn't kicked on for a hour and half now for a 2100 sf house. LOL
 
LCoop said:
If you hooked up 110vac directly to coils and it's drawing the amperage it's suppose to I'd have to say it's the wrong bricks. Rewiring for 220vac will only help a little. I disagree with Natlek. INUSULATION is everything. I built and live in a super insulated house! Trust me my energy costs to heat and cool would amaze you. So low they won't put us on a budget. lol BTW my heat treat oven is super insulated too 240vac. Goes to 1975 in 35 minutes and holds it within a degree as long as I want it or need it too. You can put your hand on all five walls that are super insulated while it's at temp and hold there forever. Now the door that's not super insulated beware after it's to temp.
Click to expand...
No , you don t disagree with me :) We are on same page about insulation https://bladeforums.com/threads/diy-heat-treat-ovens-specific-design-questions.1714753/
I m all in for proper insulation :thumbsup: I am trying to say here that there should be limit when we say .......... enough of insulation .After all day working , in the morning every HT oven should be cool ,some faster some slower ..depend of insulation ;)
 
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