I'm looking to replace the control board in an industrial air cleaner with something that I can both control from a remote station (These will be mounted in the air) and either control/monitor status from a SCADA or Grafana type setup. The circuitry seems very simple and I believe just connecting power to the proper lead on the motor will dictate which speed it runs at.
The motor nameplate itself shows amp ratings of 9 / 6,5 / 4.5, which I'm assuming corresponds to H / M / L. It looks like the Opto has a relay rating of 10A, but I would worry about the spike in current on startup, not to mention there are not enough outputs to utilize all speeds on two air handlers with one Opto.
Would an industrial arduino or the like controlling a couple SSR's or relays work best in this situation? Aside from monitoring, I would like them to run on a schedule as well as being able to push a physical button (or HMI) to turn on at will without disturbing the schedule. Thoughts?
Please do not do anything based on that schematic. It shows the main switch connects to hot line wire to ground. Also the main wire going to the motor is connected at the same time as any of the three marked speed control wires. This will result in SMOKE!
I modified a similar air handler years ago to make a high power portable fan for my business. The air handler had a large squirrel cage fan and the 4 speed motor. The motor, itself had the wire colors for each speed. I used a large rotary switch for each speed with an off position between each speed contact.
I am willing to bet your device is identical to what I used. Ignore the schematic. Connect the common wire to the common on your 120 volt circuit. Then connect, one at a time, to the 4 power wires from the motor.
What ever you decide, DO NOT connect any of the 4 speed control wires together. That will just short the windings together.
If you use SSR for the speed control, be doubly sure to never allow two relays to be energized at the same time!
Yeah the schematic is a little odd. The actual board proved to provide a little better information. It is using 3 relays to switch the neutral between the 3 different speeds to the motor with the opposite end being connected to L1. I tested that switching either Neutral or Line to each of the leads worked to spin the motor at the different speeds.
The circuit should be really simple to do and I did confirm that the draw is just over 9A on high. As I said, I'd worry about the inrush current on startup for relay choice. The other thing I need to figure out is if I want to just run all 3 lines (plus N and G) all the way back to a controller,or do the switching at the two units locally and just run 24V signal lines to the units.
I did it with three relays where the NC was wired to the common of the next and the NO went to a speed winding. No matter how messed up the code got only one speed was selected. Selection more then one at a time burns them up.
Something like this with relay logic would work. Two relays at each unit, or one 30A relay with 10AWG running to each. Then I would only need the 4 digital outputs at 24V to control on/off, and speed.
