Heat Treat Oven SSR Issue

L

lapsjd

Joined
Feb 23, 2017
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I've spent weeks reading and studying the various posts regarding HT ovens and decided to throw my hat into the ring. I'm running into a problem with the SSR though. The wiring is a 220v - 2 SSR setup. I followed the sticky when wiring. My issue is, I'm reading 220v between terminal 2 on both SSRs all the time. It doesn't matter if the door safety switch is depressed or not. Am I right that I should only read 220v across both terminal 2's only when the door switch is depressed and the "heat on light" is lit?

When I depress the door safety switch, the SSR lights both light up and I still read 220v across both Terminal 2's. When the door safety switch isn't pressed the lights go out and I still read 220v.

What am I missing? Picture posted below for reference.

29goo49.jpg
 
Not sure if this is your issue, but I know I just learned the other day, you have to have a load on the ssr. I have a light that I wired to come on and off with the elements of my PID for quench tank and didn't have a load on the ssrs except for the small light and the light was always on. When I hooked a bigger load to it it acted normal and the light went out when the ssr had no signal. Hope that helps, idk I'd have to look close at the diagram and see what's going on possibly.
 
Solid state switches (SSR) tend to leak a tad of voltage at extremely low current drain. Put a load on it and see if the voltage doesn't go away with SSR turned OFF.

Ooops, see Marc just mentioned that.

Ken H>
 
As said above, there will be leakage. It will be very small (milliAmps, maybe microAmps). You only see the Voltage because the circuit resistance is very high. Connect the elements and you'll see milliVolts/microVolts instead.

I use a plug-in control box that has an LED in parallel with the feed out to the elements. If I power it up with the output side disconnected, it lights dimly with the SSR off and brightly with the SSR on.

With the oven connected, the LED is off when the SSR is off.
 
I agree. The first thing I spotted in the photo was that there was mothing connected to #2.
 
Thanks for the info guys. I didn't expect the voltage leak. I was expecting to read zero across the 2's. Makes sense now. I'll try it out tonight.
 
A 250 Volt 100 watt light bulb placed across those terminals should not light, as it draws an actual current. What you are probably reading is called a floating voltage. You can read it in all sorts of electronic circuits if you don't use a probe with a resistor to add a small load.
 
As stated, you are measuring "leakage". Its normal of how the electronic switching of SSRs work. That current is low, in the microamps range. When "off", If measured with a load applied, the meter will read zero volts. Essentially the leakage is short circuited.

Amusing aside.
If an SSR is switched on, its not really "on" until a load is applied what completes the circuit to allow it to switch on.
The slight voltage drop across a SSR is also the voltage source for its electronic brains to operate.
 
Lieblad said:
As stated, you are measuring "leakage". Its normal of how the electronic switching of SSRs work. That current is low, in the microamps range. When "off", If measured with a load applied, the meter will read zero volts. Essentially the leakage is short circuited.

Amusing aside.
If an SSR is switched on, its not really "on" until a load is applied what completes the circuit to allow it to switch on.
The slight voltage drop across a SSR is also the voltage source for its electronic brains to operate.
Click to expand...

This is why there needs to be a load connected to complete the circuit, even when the SSR is not in the ON mode. I hope Professor Tony sees this thread. He can explain it very accurately.
 
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