I have a valve actuator which operates at 24vac/.65 amps. I have obtained a multipurpose (8-16-24v) transformer (the only 24v transformer I could find in the short term) with three terminals on the secondary side. The only information included as to how to obtain 24 volts is embossed on the face of the transformer itself. An arrow pointing to the leftmost screw is embossed 8v. An arrow pointing to the rightmost screw is embossed 16v. An arrow from the leftmost screw to the rightmost screw is embossed 24v. The third screw, I assume to be common (ground).

To obtain 24v, do I connect together leads from both the 8v terminal and the 16v terminal to form the 24v lead to my actuator input? If not, how? Thanks for your help.
Ed Pledger

Look at it this way (0 - 8 - 16 - 24). To get 24, you connect one wire to 0 (common) and the other to 24. You could get 16 volts by connecting to (0 and 16) or (8 and 24).

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Originally Posted by EdPledger

I have a valve actuator which operates at 24vac/.65 amps. I have obtained a multipurpose (8-16-24v) transformer (the only 24v transformer I could find in the short term) with three terminals on the secondary side. The only information included as to how to obtain 24 volts is embossed on the face of the transformer itself. An arrow pointing to the leftmost screw is embossed 8v. An arrow pointing to the rightmost screw is embossed 16v. An arrow from the leftmost screw to the rightmost screw is embossed 24v. The third screw, I assume to be common (ground).

To obtain 24v, do I connect together leads from both the 8v terminal and the 16v terminal to form the 24v lead to my actuator input? If not, how? Thanks for your help.
Ed Pledger

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But... read my first question again. There are only 3 screw terminals on the secondary (left, center and right). The embossed 8v points to the left terminal. The embossed 16v points to the right terminal. NOTHING points to the center terminal (which I presume to be ground). An arrow connecting the left (8v) terminal to the right (16v) terminal is embossed 24v. Logic would seem to tell me to use the left and center terminals for 8v, the right and center terminals for 16v. It seems, then, that you must combine left and right terminals (8v and 16v) on one lead to use with the center terminal to get 24v.

Please provide the make and model number of the transformer.

Each manufacturer does something different with labeling.

That and pictures help prevent guessing, with minimal info, that is the best anyone can do.

Ed:
Based on your better explanation. It would be my best guess to connect your load between 8 and 16. If you have a voltmeter, measure it. If you don't, go get two low current 12 volt bulbs and wire them in series. Connect the series combination together an look at the brightness of the lamps.

With three terminals, the most likely is a center tapped transformer, but not with your markings and 3 terminals.

You have to know a little about transformers. 1) windings can be placed in series or parallel. When in series, the voltages add or subtract. 2) When in parallel, the voltages of the windings must be identical. The resultant voltage will either be 0 or the voltage of the winding. The currents add.

With 3 terminals and different voltages a parallel combination is a no no, so connecting 8 to 16 and using the center terminal doesn't make any sense.

Since you have a arrow from one terminal to another with 24 volts marked on it, surely they have 24 volts between them. The center terminal isn't so much a ground as just a tap positioned to give 8 volts from one end, and 16 from the other.

Plug into AC, Test and write down all secondary volatge combinations with Meter.

Your original assumption was correct. You connect 0/ground from the actuator to the 8v terminal, and hot from the actuator to the 16v terminal.

Gentlemen, you've been very helpful. Turns out that a lead from the 8v terminal and one from the 16v terminal connected to any two of the three leads into my actuator supplied the 24 volts necessary to rotate the cams. But I had to select direction manually with a built-in toggle switch on the actuator. Flip it one way, it turns left, flip it the other, it turns right. Microswitches in the actuator turn the current off when the can hits a stop.
By hooking the 8v lead directly to one wire of the actuator and the 16v lead into the input of a SPDT toggle switch with the outputs to each of the other actuator wires, I can leave the toggle on the actuator on either direction and change the direction remotely by flipping the SPDT toggle. Mission accomplished and I thank you all very much.
EdPledger