Wiring a Heat Treat Oven

I know the controller output to the SSR is 8V, 40mA. The switch I have is rated for much more than that.

I don't have information on the amperage draw of the controller. I know it's likely not much, but I'll try to find out something on the support page board or try the method pso mentioned.

Thanks again for all your help!

--nathan
 
silver_pilate said:
Oh, and BTW, the reason I haven't posted the specs on the controller is that I don't have many. I've got a very rudimentary manual to help me program, but this is a generic type controller, not a name brand. According to the details I have, the wiring to the controller is correct, and I know the controller is rated to take 110 or 220, AC or DC.--nathan
Click to expand...
How's your heat treat oven going? I have been away from the computer about a week due to the southern cal fires but am back on-line and saw your thread. I built a similar HT oven a few months back and have many schematics and pictures you can use if you wish. My controller is from Auber Industries http://auberins.com/index.php?main_...s_id=4&zenid=d0e3aa43e762e959490a3fab8cb8369b and works very well. They will send you a full .pdf version of the manual if you send them an e-mail requesting one. One change that I made recently to my oven is the addition of a small computer type fan over the SSR. I was having problems with the SSR sticking in the ON position eventhough the controller did not tell it to stay on. This was due to the SSR overheating. Once the fan was added, the problem was resolved. I do have it mounted on a heat sink but I guess that was not enough.
I'd like to give credit to rashid11 for helping me with figuring out how long the coil wires should be to achieve the proper amp rating. Thanks rachid11.
Here is a pic of the schematic for my oven:
.OvenSchematicV1R-.jpg



Cranked out both elements in about 30 minutes. Have used the oven six times now with great success.
 
Last edited:
Sorry my first image post did not work as expected. I'll try again...

silver_pilate said:
Oh, and BTW, the reason I haven't posted the specs on the controller is that I don't have many. I've got a very rudimentary manual to help me program, but this is a generic type controller, not a name brand. According to the details I have, the wiring to the controller is correct, and I know the controller is rated to take 110 or 220, AC or DC.--nathan
Click to expand...
How's your heat treat oven going? I have been away from the computer about a week due to the southern cal fires but am back on-line and saw your thread. I built a similar HT oven a few months back and have many schematics and pictures you can use if you wish. My controller is from Auber Industries http://auberins.com/index.php?main_...s_id=4&zenid=d0e3aa43e762e959490a3fab8cb8369b and works very well. They will send you a full .pdf version of the manual if you send them an e-mail requesting one. One change that I made recently to my oven is the addition of a small computer type fan over the SSR. I was having problems with the SSR sticking in the ON position eventhough the controller did not tell it to stay on. This was due to the SSR overheating. Once the fan was added, the problem was resolved. I do have it mounted on a heat sink but I guess that was not enough.
I'd like to give credit to rashid11 for helping me with figuring out how long the coil wires should be to achieve the proper amp rating. Thanks rachid11.
Here is a pic of the schematic for my oven:
.OvenSchematicV1R-.jpg


Here is are some more pics of the wiring and controller layout:
ControllerBoxLayoutV1Rx-.jpg

ControllerSetupV1R-.jpg


Here is the start of the controller box wiring after folding the sheet metal:
StartCointrollerBox.jpg


Here are some pics of the HT oven almost done:
FinishedOvenAngleView.jpg

FinishedOvenSideView.jpg


Here is a pic of the HT oven holding nicely at 1875 degrees:
HTOvenAt1875.jpg


Here is a pic of a D2 knife still in ss foil wrapper after 40 minutes at 1875 degrees:
HTOvenInAction.jpg


I do not have an on/off switch so I just unplug from the wall prior to sticking my tongs into the chamber for knife removal. Hope this helps. Are you winding your own elements? I found it very easy to wind by hand by putting a 1/2 inch rod in a drill press, unplug from power and removing the drive belt to make it turn easy then turn the chuck by hand.
WindingElement.jpg


Cranked out both elements in about 30 minutes. Have used the oven six times now with great success.
 
Hey efleming

Your set up looks pretty well made. The only thing that you may want to do is to cover up the SSR and it's terminals. It appears that the two thick white wires connect the SSR to the mains supply and to the heating coils. The exposed lugs on these wires where they go into the SSR are live so you will get zapped if you happen to brush by them while working.

Take care.

Phil
 
pso said:
Hey efleming

Your set up looks pretty well made. The only thing that you may want to do is to cover up the SSR and it's terminals. It appears that the two thick white wires connect the SSR to the mains supply and to the heating coils. The exposed lugs on these wires where they go into the SSR are live so you will get zapped if you happen to brush by them while working.

Take care.

Phil
Click to expand...
Hello Phil, good item to point out. These pics were taken on initial build when not every detail was buffed out. I had since added an enclosure around the SSR and a 12V DC computer type fan over the SSR to ensure it stays cool. Anyone building this type of rig needs to cover hot leads to ensure safe use. Thx.
 
I got an Auber Industries PID also and I got mine confused some how and emailed them on a Sunday and to my surprise they emailed me back almost right away. Got it going again and was a happy camper. I recommend these guys. You will get personal service. Jim
 
eflemming,

Great pics and helpful schematics. I've got the build complete and I'm just waiting for the thermocouple to arrive and get it installed before I crank it up.

I'll post some pics when it works!

--nathan
 
What kind of thermocouples are you guys using and where did you acquire them? The one that came with my PID doesn't look like it'd be much use.

 
Solid state relays are nice but for this type of application it is much better to use a contactor for control of power to the heating elements. This way you break power to the elements at the same time and also keep from having any voltage present when the unit is not heating. Be sure to use a properly sized cable to go from your dryer outlet to your oven as well as inside your control box. Wire sizing can be just as important as the components you use.
 
I believe a ssr does exactly the same thing as a contactor an as there are no actual contacts to arc they will alst way longer. Even most motor controllers are going away from contactors. Properly wired the ssr will drop both elements at exactly the same time and you have to have power to work the a regular relay the same as a ssr.
 
Sleepy is correct that the coils will still be live (110 V wrt to ground) when the SSR is off. This is because the 230 V is really two 110 V phases where both are live. Using two SSR's would fix this. Otherwise one would have to unplug the oven to make sure that the coils were not live. One could use a contactor as Sleepy says but it would have to be a two-pole contactor.

The conductors in a circuit are components and they are just as important as the other components. A lot of the work I have had to do to fix up a product is to put in the correct wiring where a previous engineer had just slapped in some wires without giving proper consideration.

The following explains SSR's better than I can.

http://en.wikipedia.org/wiki/Solid_state_relay

Phil
 
SSR's work great for applications where small leakage currents are no problem. In this type of application the leakage should be no issue and as long as the power is completely disconnected before messing with the wiring there is no real hazard.

Contactor:
Pros: full isolation when off, high current, no internal heating when on, tough, 2 and 3 lines per unit easily available
Cons: noisy, possibly shorter life (but not necessarily, SSRs can be burned up), moving parts may mean wear issues but generally rated in the 100k+ cycles, may be slower switching

SSR:
Pros: no moving parts, quiet, easy to wire, may survive more cycles, may be faster switching (immaterial for a kiln)
Cons: allows small current to flow even when 'off' (shock hazard), can be burned up with overcurrent pretty easily, one line each

I will go with whichever I can get cheaper at the time when I build my salt pot controller.
 
CDH said:
SSR's work great for applications where small leakage currents are no problem. In this type of application the leakage should be no issue and as long as the power is completely disconnected before messing with the wiring there is no real hazard.

Contactor:
Pros: full isolation when off, high current, no internal heating when on, tough, 2 and 3 lines per unit easily available
Cons: noisy, possibly shorter life (but not necessarily, SSRs can be burned up), moving parts may mean wear issues but generally rated in the 100k+ cycles, may be slower switching

SSR:
Pros: no moving parts, quiet, easy to wire, may survive more cycles, may be faster switching (immaterial for a kiln)
Cons: allows small current to flow even when 'off' (shock hazard), can be burned up with overcurrent pretty easily, one line each

I will go with whichever I can get cheaper at the time when I build my salt pot controller.
Click to expand...

SSRs also have the ability to fail shorted, providing constant power to the coils ruining the piece being heat treated or even causing a fire. A high temp cutoff of sorts is always a good idea. Even just a simple thermostat or if your controller has 2 setpoints then you set it up for this event using on/off control.

One problem to be aware of with thermouples is when they may short. At the short they will indicate ambient temperature at the short. (Try this sometime. Short across the TC terminals at the controller and your controller will read ambient temperature.) When this happens, it will ask for full output and will again, ruin your piece.

If you don't have the ability to have a high limit cutout or shutdown, don't use it unattended.

Congratulations on your new oven by the way.

Craig
 
SSR's are not unique in that, but that is a good point I had missed. Contactors can stick, they rely on spring power to unseat and open the circuit, especially if you don't keep them away from grit. They will usually handle fine dust without a problem.

Building a unit with some failsafe features really elevates the design to another level. Redundant controls is another option. Some controllers will allow dual inputs. the options are wide and as varied as the knife designs here...and probably not worth it for anyone short of a production scale shop.
 
CDH said:
SSR's are not unique in that, but that is a good point I had missed. Contactors can stick, they rely on spring power to unseat and open the circuit, especially if you don't keep them away from grit. They will usually handle fine dust without a problem.

Building a unit with some failsafe features really elevates the design to another level. Redundant controls is another option. Some controllers will allow dual inputs. the options are wide and as varied as the knife designs here...and probably not worth it for anyone short of a production scale shop.
Click to expand...

If the controller has a dual input you can wire a contact cutout from the controller's alarm terminals as a high temp trip. I recommend using an additional thermocouple for the second input and not having just one wired in parallel. Pretty simple, pretty inexpensive.

Craig
 
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