I need some help...I'm trying to automate my methanol recovery still. I have a PID controller, but need to hook that up through a relay to control the heating elements.

The thermocouple and controller are working as expected, but I'm not smart enough to figure out how to hook up this relay (and not brave enough to just start applying power to it and wait for smoke).

Check out Page 4 of the PDF at this link.
The "standard type" is the first pin arrangement shown, and is the type I have.

As I understand it, I apply the "hot" side to terminal 1, and terminal 3 will provide power when the relay is activated. Same for 8 and 6.

I don't know what I need to do to get the relay to turn on. I have a 5A AC output coming from my controller...but I don't know what terminal to hook it up to (and if I need to deal with the neutral leg of the circuit coming from the controller).

Please let me know if you can provide any guidance...or if I should stop now before I hurt myself. Thanks! Dan.

Hi Dan

This is the scheme to use, make sure you have the same relay part number as shown on the diagram below, because the 1st relay you mention on page 4 is for a DC coil only.

Your relay coil should be the 110V type

Your heater should be no more than 1.5kW if you are using this relay - its contacts are rated at 10A max, so 20A max if using both sets of contacts, so derate to 1.5kW to give youself some safety margin and to increase the life of the contacts.

The heavy red wiring carries the heater current, and must be sized accordingly.

The thinner red wiring carries the relay drive current only.

Make sure your 120V feed is fused appropriately to the load and the cable size.







In words ...

1. Your controller's 120V relay output goes to pin 2 of the relay.

2. Pin 7 of the relay goes to neutral

3. 120V line goes to the to terminals 1 and 8 of the relay, and to the controller's output relay.

4. Pins 3 and 6 of the relay go to the 120V terminal of the heater.

5. The neutral end of the heater goes to neutral power feed.

hope that helps,

regards,

Graham

Works great! Thanks. I do have the AC relay and am running a 4500W 220V heating element on 110V...so I'm at 1125W keeping me well within the margin of error when using both contacts of the relay.

Now it makes sense that terminal 7 needs neutral to complete the "relay activation" circuit when 2 becomes hot.

I'm on a 20A circuit but will double-check the wire sizes and circuit breaker as you suggested.

...and to think it all worked with no sparks or smoke. Thanks for your help. Dan.