usa knifemaker HT oven?

P

Pelallito

Well-Known Member
If you already have a pid controller set up, is there any reason that you could not use it to control the kd 8414 oven? Plug the oven into your control box with two SSRs, one for each hot leg and pid plus thermocoule hook up, and the oven into your NEMA 6-15P 15amp 250v plug, 9 amp source.
Could you leave the dial set for maximum and let the pid do the controlling?
The PID would be this or similar-http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=4.
Would this work?
Fred
 
Well, "IF" the KD8414 is only a t'stat it would work nicely - and from the description I suspect that's what it's got. By setting the t'stat well above the control range of the PID controller, it'd sit there happy and work just fine. "IF" it has any type of electronic controller, then - nope, won't work. The PID controller using a SSR would normally be set for PWM output for tight temperature control, and any electronics won't like PWM at all.

Your idea is exactly what I thought about doing with the new Evenheat with SetPro controller I've got. The SetPro "seems" to be OFF/ON rather than analog PWM control. Not near as tight a control as I was expecting.

I'll be looking to see what other folks who actually know the KD8414 oven says.

Ken H>
 
I figured someone with real knowledge of the KD oven would have chimed in by now. Oh well - maybe soon.

I ordered the KF18 - PWM is "Pulse Width Modulation" which is the way to control the amount of energy under the AC voltage - it's usually no long a true sine wave, but more of a "modulated square wave". This is one of the methods used by a PID controller to very closely control the temperature. As the temperature setpoint is approached, the controller starts cutting back on the amount of energy going to the heating coils so there is less overshoot of temperature before complete turn off of energy. Then, as temperature starts falling and approaching setpoint, a small amount of energy is applied to heating coils.

I use this type of control for my tempering oven and am able to control temperature ±1ºF as a general rule.

The temperature in the EvenHeat oven varies a good bit from bottom to top - at 800ºF the oven can be 60ºF hotter on top than in bottom of oven where the blade is lying. I've been considering drilling a hole thru the bottom to insert a ThermoCouple to bottom so the SetPro would be controlling from temperature of blade, rather than the hotter temp at top of oven. I do think perhaps the KD oven with the TC probe in center of back might better indicate true temperature of blade.

I should have purchased the KD oven, but I was sorta wanting the 18" size. Oh Well.

Have fun - I'm sure the KD oven will really work good with the Auber PID controller. Since I'm "assuming" it's a simple t'stat, it should be a simple matter to set t'stat to max temp, and use the Auber PID controller with SSR to get really good control - MUCH better control than the EvenHeat ovens.

Ken H>
 
Rudy Joly and KenH, thanks for the response and help.
I took another look at it, the KD oven. I would have to either take it apart to get access to the TC or drill a hole for another TC connected to the PID. Either of those moves would cancel the warranty.
I am torn between buying the oven or building one. Like you KenH, I want one that is 18" or just a little longer.
Fred
 
Fred, I expect the KD oven will have the TC accessible from outside as does the EvenHeat oven. The EvenHeat TC is a large solid wire inside a ceramic covering that extends to a ceramic terminal strip on outside of oven, and due to high level of heat inside oven, that's about the only valid way to do it. Of course, that terminal strip could be inside a metal shell on the KD oven.

BTW, in the link Rudy gave one post said the amount of heat generated by the SSR is a function of amps..... I think you'll find it's a function of watts.

Ken H>
 
KEN H,
I looked at the photos on USA knifemaker and could not see any external wire, that doesn't mean it isn't there. ;)
Is this the information you were refering to?-If you have the choice between 110V and 220V for the power feed to the elements, 220V is the better option. The heat generated across the SSR is dependent on the current passing through it. For a given power, the current (Amps) will halve if the voltage is doubled. The SSR will then only generate half the heat for you to get rid of.
My SSRs are rated 25 amps each, which seems to be heavy enough for this application. Or at least they were recommended somewhere in my reading. If you think that they are not big enough, I will go larger. Here is a link-http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=9
I got everything from Auberins. I also got the heat sinks and paste from them. I need to pick up a fan and a slightly larger box to enclose everything.
I will folow this wiring diagram-
http://www.bladeforums.com/forums/s...eat-Treat-Oven-Wiring-Schematic-Future-Sticky
Thanks again,
Fred
 
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Fred, that's a great schematic you linked to with good info.

I would ask a question about your statement that heat dissipated by the SSR is solely a function of amps passed thru. I was thinking heat dissipated was a function of watts dissipated..... remember, watts = amps X voltage. Am I missing something?

Ken H>
 
Ken H,
I was quoting from the link Rudy Joly posted. I don't know enough about electricity to argue it either way. Tuesday I will ask electricians or instrument techs about this.
Thanks,
Fred
 
Fred, I will be interested in hearing what your folks say about that. It is easy to get confused on the difference in use of 120VAC vs 220VAC. I've heard folks say a pump (or heater) on 220vac uses half the power that a 120vac because the amps are half on 220, but the power is exactly the same volts X amps.

Ken H>
 
Gentlemen,

A 20 amp 110v circuit uses 20 amps on one power leg. A 220v 10 amp circuit uses 10 amps per 2 legs. Total power consumption is 20 amps either way. The real reason to use 220 is the savings in both materials to run the circuit and the heat loss should be less at lower amperage draw. Most SSRs are rated in amps, you would need one per leg to meet the needs of a 220v oven. Remember to get one that is rated 25% more than you need.

I was a State Registered Electrical Contractor for 10 years and grew up in the industry. I'm an EEE Engineer. I hated the family business and left it years ago.
 
Exactly correct George - 2200 watts anyway you figure it. 110 volts at 20 amps is 2200 watts, 220 volts at 10 amps is still 2200 watts.

I retired in April doing I&E engineering work for many years myself. No magic bullet.

Ken H>
 
Ken,

We need to do a thread on basic electrical things that would help most folks understand the mystic powers of the unseen and unknown. Something that could possibly be pinned in the tools section. A thread that would explain why to use 220v, when to use it, and why something are better to run on it. Why does a 2 hp motor run at 2 hp on a 220 circuit and if connected to 110v that same motor at max produces 1.5 hp. Shop info for the common man, I mean person. (my contractor daughters just walked in on me.) LOL
Just thinking out loud.

George
 
TacticallySharp said:
Ken,

We need to do a thread on basic electrical things that would help most folks understand the mystic powers of the unseen and unknown. Something that could possibly be pinned in the tools section. A thread that would explain why to use 220v, when to use it, and why something are better to run on it. Why does a 2 hp motor run at 2 hp on a 220 circuit and if connected to 110v that same motor at max produces 1.5 hp. Shop info for the common man, I mean person. (my contractor daughters just walked in on me.) LOL
Just thinking out loud.

George
Click to expand...

That is a great idea. I think many would enjoy the info and benefit greatly while being safe. The wives would be happy. :)
 
I'm sure it would be fun to do some basic electric thread. A short explanation of why a SSR is different than a mechanical relay might be a start?

A SSR has a certain amount of resistance across the SCR inside the SSR that does the function of dry contacts in a mechanical relay. A voltage drop across a known resistance is solely dependent on amps - NOT volts. A 1 ohm resistance in anything, be it resistor, length of wire, or a SSR will cause the same voltage drop regardless of voltage in circuit. Thus a 1 volt drop across a SSR at 10 amps is 10 watts of heat to be dissipated - makes no difference if there is 120 volts or 240 volts flowing "thru" the SSR. The watts of heat generated is solely a function of the amps for a SSR.

Now George, perhaps you can teach me why a Reliance 2hp motor with a nametag that says 120VAC = 2hp, and 220 VAC = 2 hp really is only 1.5 hp at 120 volts. After all, a dual voltage motor is basically two 120 volt winding inside, paralleled for 120 or series for 220 volt operation. Are you assuming sufficient voltage drop to reduce hp?

Always looking to learn something new.

Ken
 
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