Auber Instruments HT Kit

bmilleker

bmilleker

Joined
Nov 26, 2012
Messages
548
I am in the process of putting my oven together. I am building close to the specs of the Evenheat 18" model, but with more power (3600W). As far as electronics are concerned, Auber Instruments has a kiln/HT oven kit (https://www.auberins.com/index.php?main_page=product_info&cPath=58_55&products_id=677). I priced out all the components myself, and decided this would be a decent route to go. They provide detailed instructions on the wiring after your purchase the kit. The instructions are well done.

My only concern with this kit, is the single SSR. I even raised this with them and the response I got was:

Our existing power system design uses a single pole SSR to cut one hot line to the output; but there is a contactor built inside to turn ON/OFF the input power. If you want to change our design, you will need to upgrade the heat sink to 60A; our 40A heat sink only has the holes to mount one SSR, but the 60A heat sink can mount 2 x SSR.
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The design of our power system uses 3 pole contactor to completely turn ON/OFF the input power; for output heating element, we use a single phase SSR to cut one pole of the hot line. SSR is an electric switch and will have some leakage current (about 10 milliamps). Normally people don't build a control panel with two SSR (each cutting one hot line for 240V); because two SSR will generate double of the heat and requires a larger heat sink. Even if using two SSR (one cuts L1 and One cuts L2), the small leakage current is not enough to drive a 240V heating element but one will get shock if touching it by hand.


If you want to add safety to the control box, I would recommend you to install in on a GFCI protected circuit; thus, in the case if there is a short between hot line and ground, GFCI will be triggered and cut off power.
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What do you guys think? Any modifications that you guys would make to it?

From my understanding, and I could very well be wrong, the use of the contactor is turning off the SSR and the other leg if the power is cut off. Simply flipping the heater switch off just turns off the one leg.
 
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I like it a lot. I recommend upgrading to double SSRs and the larger heat sink.

You could cobble all the parts together for a bt less probably, but as a full package, it looks like a good deal.
 
I can’t see why thy would ever recommend a single SSR unless your building a 120v oven ONLY. Shock hazard to ground if running 240v
 
Thank you guys. I would love to post the schematics, but I don't want to infringe on any of Auber Ins. IP.

I believe that the contactor shuts off both legs when the power switch is flipped off. I could put a door switch in line with this signal wiring for the contactor. This would also cut the power to the PID controller, but is that such a big deal? The PID controller can be set to go back to its last programming. So if I peaked in the oven for whatever reason, and closed the door again, the oven will resume its programming.
 
A door switch controls the low voltage/low current line to the SSR. If you put it in the hot line to the coils it would be fried fast.

Place the door switch in one of the two lines from the PID control voltage terminals (usually labeled +/- DC out) to the SSR control terminals (Usually #3&#4, labeled +/- 3-90DC). It doesn't matter which wire you put the switch in. When the door opens, the control voltage stops, and the SSR shuts off. With two SSRs, you still have only one pair of wires from the PID. The two SSTs are jumpered together in parallel for the DC control voltage.
One SSR gets 220 VAC line A and the other gets 220 VAC line B, both on terminal #1. The coil ends go to terminal #2 on each SSR.

Yes, one could shut off the main breaker to kill the power to the coils when you put in or take out a blade, but that would shut down the PID ... which would be a really bad idea. It would be like shutting the engine off on a car instead of putting it in neutral.

I have been promoting two SSTs for a while. I think the idea has finally caught on. You wouldn't believe the engineers (some from from kiln companies) who ask "why?"
It is just plain good sense and safety. The additional cost is usually less than $30.
 
I should clarify. The door switch would be placed on the signal wire of for the contactor, not on a hot line. This turns the power on and off. But like you just mentioned, turning the PID controller on and off like that wouldn't be a good idea.

I already have the kit, but it shouldn't be an issue adding in the second SSR and larger heatsink. I will still use the contactor and the rest of the schematics from the kit, and just modify to use the second SSR.

Thank you for the feedback. I really appreciate it.
 
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