The bath control is probably the most unappreciated additions to a Rinnai Tankless water heating system. The bath control is designed to be installed in the same room as a bathtub. It is hardwired so keep that in mind. Once you set it up with the size of your tub you simply tell it what temperature you want the bath water to be and the controller will fill the tub to temperature and shut the water off to the tub all on its own. When you come back to the tub it is full of water at the temperature you requested. This is possible because the Rinnai water heater actually has a solenoid that can shut off the hot water supply. This controller can access that solenoid. It also has an intercom type system that allows calls between the main control and bath control.
Placing the main control close to your kitchen sink can also have a lot of benefits. including being able to turn the hot water to a much higher setting for situations that require it. Once you have finished your task you can immediately return the water heater to a lower safer temperature. It will also let you know if your Rinnai unit is experiencing any problems.
The set is listed as working with R50LSi, R53iPLUS, R75LSi, R85ePlus, R85IPlus, R94LSi, R94LSe. This control should also with the Jacuzzi brand tankless water heater made by Rinnai. Check with the Rinnai or a licensed professional first before ordering.