SSR partial fail?

[BBBF]

I switched my element on and it didn't seem to be doing anything. I visually checked the SSR and the led on it was flashing on and off as expected. I checked my PID settings to make sure I didn't have a low ramp up %. All settings looked fine. Plugged the element directly into the wall outlet and it starts heating up. Plugged a fan into the element outlet and nothing happens..

I get out the volt meter and start to check the wiring. No lose connections, everything is checking out except there is 122v going into one side of the SSR and only like 30v coming out. I switched the fan out with a lamp and there was a dim glow.

Can a SSR fail like this? I thought the options were fail open, fail closed or burn up. I don't understand how the voltage would change.

 

[day_trippr]

Well the gamut of SSR failures is surely wide enough to encompass an impedance shift.

Personally, the burn-up thing is the one that bugs the **** out of my going electric

Cheers!

 

[doug293cz]

SSR's normally fail in the "ON" state, but that doesn't mean that's the only way they can fail. The LED on the SSR only tells you that the SSR is getting a valid trigger signal (from the PID.) It tells you nothing about what the output portion of the SSR is doing.

There are actually two LED's in the SSR. There is the visible LED on the front of the SSR, but there is also an infra-red LED (electrically in parallel with the visible LED) inside the SSR. The IR LED is used to send a trigger signal to an IR receiver (photo diode or photo transistor) that actually triggers the TRIAC (the solid state switch) inisde the SSR. If the receiving trigger circuit, or TRIAC fails, this will not affect the visible LED.

SSR's are also complicated to test. If you are using a voltmeter to test, the SSR needs a load attached in order to get useful information. Read this post which explains how an SSR behaves electrically.

Brew on

 

[augiedoggy]

If its one of the white fotek clone style ssrs its fairly common to see failure.

 

[BBBF]

Cheap, questionable quality SSRs are the most likely problem. The change in voltage just seemed odd from my overly simplified thoughts on SSRs, ie it is like a switch. Closed = 120v passes through and open = 0v. Needed to hear I wasn't crazy or missing something