Specific SCR wiring question

[nobadays]

Hey all in the know... I bought THIS SCR to control a 5500w element on a pot stil..... I mean a hand cleaner making apparatus! I am fairly knowledgeable on electrical circuits including control circuits but I find myself a bit baffled here. Specifically how to hook the wires up to this SCR. I think I know but I am certain many of you will positively know!

My understanding, correct me if I'm wrong, is that only 1 leg to my element is actually controlled by the SCR. This SCR has 2 input/output terminals. So just out of curiosity I put the volt ohm meter to the terminals and the 2 inside terminals are apparently bridged on the circuit board. Normally I would wire input/output terminals identically... i.e. white/black on the input, then white/black on the output.

I guess my ultimate question, since, again my understanding is only 1 leg is regulated by the SCR, do I wire this: white/black - black/white. In essence this would allow the white leg to be regulated while the black leg passes directly through to the element.

Thanks in advance!

 

[doug293cz]

SCR's control power by turning current on and off. Since current flows in a loop, interrupting the loop anywhere will stop the current. Good design practice says that for systems with one hot and one neutral, that you switch the hot line. For split phase 240V (two hots) it doesn't matter which hot you switch.

For 120V (or single phase 240V) the neutral should be connected to the two center terminals, and hot to the two outer terminals. For split phase 240V, doesn't matter which hot goes where.

Brew on

 

[nobadays]

Just the guy I was hoping to hear from!! I had seen this picture out there but just wanted to ask before I fried something! I had found another post on an SCR that you had commented on, but on it the outside terminals were bridged. That post seemed to confirm my suspicion that only 1 leg actually passes through the SCR circuitry. Found a few other wiring diagrams that were either not color coded or no mention of terminal bridges.

Thanks Doug!

 

[RufusBrewer]

I am going to say they device doesn't look as beefy as advertised. Even when you read between the lines, it is 5,000 watts continuous, I am skeptical at the unit's durability.

The specs are deceiving. You could not run it at 220 V @ 80 amps =17,600 watts. No way.

The heatsink looks too small to handle 5,000 watts. Are the terminal blocks able to handle 80 amps? Can the terminal blocks accept a cable that is rated for 80 amps? Maybe the unit us bigger than it looks in the photo.

If you use this, I strongly suggest anybody that uses this, do so with caution. Make sure the heatsink has plenty of free air around it. Some forced convection (as in a fan) monitor the temp regularly by placing your hand on th heatsink.

 

[nobadays]

"The specs are deceiving. You could not run it at 220 V @ 80 amps =17,600 watts. No way." I agree it doesn't appear beefy enough for 80A. It shows 10,000W, I will be running a 5500w element at 240v so maximum amperage of ~23A. The terminals look to be able to handle 10awg maximum. I settled on this SCR as the reviews showed several who use it successfully in boil kettles or pot stills. An SSR would be a more robust approach but these cheap SCRs are being used regularly in the home distiller community as cheap solutions where infinite and constant temp control is needed. And yes, apparently they do burn out occasionally.

Thanks