An SSR is a triac circuit. You cannot put an LED across it (unless you install a load resistor). You should use an incandescent light. The triac can leak just enough current to light an LED (comes on at a lower voltage than a light bulb) but doesn't have enough current to drive a light bulb.
Touching this thread because I just finished wiring my control box last night and wanted to throw in here that even using an incandescent lamp, you can get some confusing results.
After I finished running the last "real" wire for the system, the only thing I had not yet connected was a small panel mount incandescent lamp because it needed to have leads soldered to it and I was waiting for the soldering iron to heat up.
While waiting, I went ahead and plugged the box in and started testing things out; flipping switches and making sure I could power up a 40W lightbulb plugged in where the pump will eventually be, making sure the PID and pulse width modulator were working, etc, etc, etc.
Everything looked great, and I was a happy man.
Now, that little lamp that I was about to solder on i sjust meant to let me know when the element is actually receiving power. My main thinking when I bought it was that it might come in handy trying to diagnose a problem without having to open up the panel and stick the multi-meter in there.
So, IRONICALLY, the lamp is intended to be a debugging device, but what I ended up debugging was the damn lamp itself.
I soldered the leads to it and connected it to the output of the SSR. When I turned the power on for the control panel, the lamp immediately lit up. It should not have been lit up. The control lines to the relay were off.
After some head scratching and multi-meter measurements, I finally figured out that enough current was leaking through the SSR to allow the lamp to light up. The lamp's resistance measured at 1MOhm and it is to be driven by 120V, so it pulls a puny 0.12mA of current when in full/normal operation. This thing is just a
14mW light bulb. I did not measure how much current was really leaking through the SSR, but it was clearly enough to light my little incandescent lamp.
I then connected my 40W lightbulb to the relay output to mimic having a heating element plugged in and the little lamp on the panel turned off. The vast majority of current leaking through the SSR followed the path of least resistance through the 40W lightbulb and only a SUPER tiny amount went to the indicator lamp. Neither device was getting enough current to actually light up.
With an added load on the output of the SSR, the tiny panel mount lamp functions as intended, but if there is no other path for the leakage current to take when coming out of the SSR, it will cause the panel mount lamp to light up.
At first, I considered this a bug, but now I consider it a feature.
(RelayControl=OFF & IndicatorLamp=OFF) means all is well, and no power is going to the heater
(RelayControl=OFF & IndicatorLamp=ON) means that I have no heater plugged in or there is a problem with the circuit through the heater.
(RelayControl=ON & IndicatorLamp=OFF) means that something is causing current to fail to come through the SSR.
(RelayControl=ON & IndicatorLamp=ON) means all is well, and power is going to the heater