easy to mount and Functional devices create just about any configuration (coil voltage and switch configuration and high amperage contacts) you want. The 1/2 inch conduit connection makes it easy to add this to any control setup. I like it because I used it to slave a set of contacts to control a Dust collector when a motor turns on. I've used Functional Devices for over 40 years and they are a USA company.

I will order again for sure.

I added two inline booster fans in my HVAC ducts at home and used a similar relay, the Functional Devices RIBU1C, to automatically turn on the booster fans when the main fan comes on. It was working perfectly until I decided to add a third booster fan. The relay failed, and the fans ran all the time, whether HVAC was running or not. When I added up the total current drawn by all three loads, I realized that adding that the additional fan exceeded the 10amp load rating on the RIBU1C. The startup load had shorted out the contact and it was always closed. I liked the RIB product, but I needed one with a higher current rating.I found this RIB2421B unit with a 20A current rating. The 20A replacement unit had the exact same wiring diagram and functionality. Since I had already wired up the 10A rated relay in my power circuit, replacement was easy, one wire at a time. The failed 10A unit is in the photo nearby, showing markings on the circuit diagram indicating how I chose to connect the power relay. These connections provide normally open (NO) operation. After installation, functionality was restored. My booster fans have been operating for months now and I've had no trouble with my setup. The adjustable booster fan speeds simplified airflow balancing in my home which had been a problem for more than 20 years. Installing fans with this power relay is far less expensive than replacing the entire duct system -- as one contractor had proposed. I saved thousands and now my home is much more comfortable, in summer and winter. This simple device makes it all work!

After getting a misrepresented hot tub controller that wouldn't run my 2 speed pump, I decided to use this relay to make my own 2 speed. Works great.