Diy heat treat oven help

Ok so, first off, winding the coil is not that hard, but having said that Kreuger will wind coils for you for a very small fee. If you click on 13ga wire there are drop down menus to have them wind it for you and twist the ends. It comes out way cheaper. That's what I did. Or at least way cheaper for the 48" oven I'm building.

I just checked their site I see where you ordered the 120VAC version. So it's either your wiring (miswired), your PID, Your PID settings or the SSR. Not sure how to check and SSR if it's working correclty, but GIYF.

Also, why are you going up to 1975F? Just curious.
 
Natlek said:
I don t get it ? You shorten element and you get more watts ? What am I missing ?
Click to expand...
Natlek said:
I don t get it ? You shorten element and you get more watts ? What am I missing ?
Click to expand...
hopefully it is me that is missing something that's why I am asking for help, maybe i got the calculations wrong
using a wattage calculator if i reduce the resistance( shorter wire ) I increase the wattage. Did I get this wrong?
Thanks
 
cartierusm said:
Ok so, first off, winding the coil is not that hard, but having said that Kreuger will wind coils for you for a very small fee. If you click on 13ga wire there are drop down menus to have them wind it for you and twist the ends. It comes out way cheaper. That's what I did. Or at least way cheaper for the 48" oven I'm building.

I just checked their site I see where you ordered the 120VAC version. So it's either your wiring (miswired), your PID, Your PID settings or the SSR. Not sure how to check and SSR if it's working correclty, but GIYF.

Also, why are you going up to 1975F? Just curious.
Click to expand...
1975f is the temp for AEB-L stainless that I want to heat treat
I also thought Pid was the problem that's why I bypassed it as per natlek's suggestion. That should eliminate PID and SSR as the problems but I did buy another SSR just to be sure
TZ
 
Ah ok on the temp.

So you can't get to that last bit of heat? Hmmm, so it's working better hooked up directly?

How thick are your walls? Evenheats have 4.5" thick.
 
cartierusm said:
Ah ok on the temp.

So you can't get to that last bit of heat? Hmmm, so it's working better hooked up directly?
I don't think there was any improvement hooked up directly, I think the improvement came from the addition of the 2" rock wool insulation I added

How thick are your walls? Evenheats have 4.5" thick.
Click to expand...
My walls are only 2.5" thick and a little less where the element is routed into the side, that is definitely where it heats up on the outside,
is it all just a matter of heat loss? many of the videos I watch and even commercial ovens seem to use standard fire brick for the walls
evenheat website says 2.5" thick for the standard oven and 3" for the KO high temp oven
TZ
 
That could be true. I was just going off internal dimensions minus external dimension.

Are you using hard fire bricks? Are they heavy?
 
cartierusm said:
That could be true. I was just going off internal dimensions minus external dimension.

Are you using hard fire bricks? Are they heavy?
Click to expand...
no I used k23 soft bricks
maybe I should order more bricks to double up on wall thickness. It is difficult to get these where i live, shipping is very expensive, that is why i did not just buy an evenheat oven in the first place
many Thanks TZ
 
You might want to coat your bricks with something like ITC-100. I built an oven recently using 2.5" thick brick and an outer layer of 1" kao-wool, and I noticed a significant improvement in holding setpoint after coating with ITC-100. Too be fair, though, I'm running 220 and a 3200W element (give or take), so I reach 1575 in about 35 minutes, IIRC. I haven't pushed it to 1975 yet, but there is a significant slow down once you get around 1400 or 1500. I would think your oven could hit those temps, on paper anyway.
 
I am following this, I will maybe rewire my oven to TC and PID soon, but I am avoiding it for the obvious reasons :)

What did the oven cost you until now if I may ask?

Good luck with your oven, I bought the same PID as you, so I am really interested how you are going to solve this. I remember there were members that needed to return their PIDs after they couldn't make them work and new PIDs solved the problem.

I was lucky and found a smallish (38×25×10 cm chamber) old industrial type oven on ebay that works just fine (used it only three times) for 380 Eur + shipping.
 
Ok was just checking that you were using IFB (insulated fire bricks, K23). Hmmm more insulation could be the culprit too. I use ITC-100 as well, but if those other items are expensive in your area then ITC will be as here in the US its really expensive.

I would keep the SSR and PID bypassed until you reach the temps you're looking for. Sorry I can't be more help. I would give Kreuger a call after the holiday weekend and ask them. They sell all that stuff and if you tell them exactly how you built it they might be able to tell you right off the bat if it's heat leak from not enough insulation.
 
You need better bricks and/or insulation. Wrapping the oven in 1" or more of Kaowool will help. Using K23 bricks from a good source also helps. All K23 bricks are not the same. 3" thick bricks are better, and for really good insulation, turn the bricks so they are on their wide side to make the walls 4" thick. I have heard of folks using then longwise when they had a large supply of used bricks from a pottery kiln. An 8" thick wa;ll would be overkill, but it sure would insulate.
 
Stacy E. Apelt - Bladesmith said:
You need better bricks and/or insulation. Wrapping the oven in 1" or more of Kaowool will help. Using K23 bricks from a good source also helps. All K23 bricks are not the same. 3" thick bricks are better, and for really good insulation, turn the bricks so they are on their wide side to make the walls 4" thick. I have heard of folks using then longwise when they had a large supply of used bricks from a pottery kiln. An 8" thick wa;ll would be overkill, but it sure would insulate.
Click to expand...

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 ?

An 8" thick wa;ll would be overkill, but it sure would insulate
Click to expand...
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
 
Last edited:
Tom Zaccagnini said:
hopefully it is me that is missing something that's why I am asking for help, maybe i got the calculations wrong
using a wattage calculator if i reduce the resistance( shorter wire ) I increase the wattage. Did I get this wrong?
Thanks
Click to expand...
No , you don t . I mixed things up.............:thumbsup:
 
Tom Zaccagnini said:
no I used k23 soft bricks
maybe I should order more bricks to double up on wall thickness. It is difficult to get these where i live, shipping is very expensive, that is why i did not just buy an evenheat oven in the first place
many Thanks TZ
Click to expand...
You have enough insulation for sure !
If you have at least one brick left, measure the weight, it should be around 2 lbs.I think you have wrong one bricks.....
 
Last edited:
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
 
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.

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?
 
just another spitball here and hopefully someone with more knowledge can chime in.

Your math looks correct, wattage per ft3 etc. However, this may not necessarily mean heat. I'm thinking that you maybe used too heavy of a gauge wire and the electricity doesn't have enough resistance to create enough heat.

You used 13ga wire which is pretty heavy. Its resistance is .1673 ohms per foot which is half of that for 16 ga. Using that resistance you were able to buy a coil of a certain length that would draw a certain amount of amps producing the wattage fer ft3 that you want.

If you shorted the coil and halved it length you'd double the wattage as your resistance would drop by half. This doesn't mean more heat though as you coil is half the length. Taking this further a 1" coil should really heat up fast if you could supply enough power and not burn it out.

There just may be too much crossectional area of wire to generate heat. I'd suggest buying a coil of 16 gage wire and make your own coil for cheap. The good thing is the 16ga wire will have a higher resistance so you need shorter wire so you can stretch the coil to fit your existing grooves. The unfortunate thing is you'll probably destroy your current element taking it out as its probably hard after the first firing.
 
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...
 
Ya i was mostly spitballing as it just doesn't make a lot of sense. I don't know a lot about electrical. I guess my though process was that a thick heavy wire at a certain length will still provide the same amperage draw and therefor wattage (voltage assumed constant) by may give off less heat. This thought process may violate thermodynamics though as the energy draw has to go somewhere and in thus case its heat and light. If 220 is an option maybe thats the way to go.



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...
 
FredyCro said:
I am following this, I will maybe rewire my oven to TC and PID soon, but I am avoiding it for the obvious reasons :)

What did the oven cost you until now if I may ask?
cost to build so far around $500us. Not worth it in my opinion, if I could buy an evenheat today I would

Good luck with your oven, I bought the same PID as you, so I am really interested how you are going to solve this. I remember there were members that needed to return their PIDs after they couldn't make them work and new PIDs solved the problem.
PID does not seem to be the problem

I was lucky and found a smallish (38×25×10 cm chamber) old industrial type oven on ebay that works just fine (used it only three times) for 380 Eur + shipping.
Click to expand...
Good luck with your oven.
 
You must log in or register to reply here.
Back
Top