In this quick installation tutorial we will help you in installing an additional Rinnai controller which is an excellent addition to your Rinnai tankless water heater, to adjust the control over the temperature and to display Rinnai error codes to identify the exact issue and solve accordingly. On a Rinnai heater there is only one controller on the front panel and for some outdoor units it is located inside the front panel. In this guide, our expert Joseph will show you how to properly and easily install an additional controller to your Rinnai tankless water heater.
Why Install an Additional Rinnai Controller?
As we install water heater in the basement, garage or even outdoors, it is sometimes inconvenient to reach the water heater location just to change the temperature. So to make it easier Rinnai tankless water heaters has an option to connect an additional controllers and fix it in a location where you have easy access.
Rinnai controllers comes with part numbers MC-91-2 for residential purpose and MCC-91-2 for commercial purposes. It comes with 1 controllers, 2screws and 2 anchors to fix on the wall.
Tools and Materials Required for Installation
Before starting the installation of the Rinnai MC-91 controller, make sure you have the following tools and materials ready:
- Phillips Head Screwdriver – For mounting the controller and securing screws in place.
- Drill – Needed for creating holes in the wall if mounting the controller on drywall or other surfaces.
- Wire Stripper/Crimper – Used to strip and prepare the wires for connection and crimping to ensure secure electrical connections.
- Additional Wire – use a non-polarized two-core cable with a minimum gauge of 22 AWG.
- Wire Nuts – For safely securing electrical connections between the wires during installation.
The maximum cable length depends on the number of controllers connected; for a single controller, longer cables are allowed, but when multiple controllers are connected, the cable length should be reduced to ensure optimal performance. Always refer to the Rinnai installation manual for precise cable length limits based on your setup.
For a single controller setup you can use a maximum of 100 meters wire, but as the number increased to 2 the wire should be under 50 meters. If the setup has 3 or more the wires should be less than 20 meters. For multiple controller setup, they should be wired in parallel and not in series.
Controller Location guidelines
When selecting a location for your controller, follow these guidelines:
- Keep out of children’s reach to prevent accidental adjustments.
- Avoid hot areas such as near ovens or radiant heaters, as heat can affect performance.
- Avoid areas prone to splashing with liquids to prevent damage.
- Keep out of direct sunlight, as it can make the digital display hard to read.
- Do not install in public areas where unauthorized people can adjust the settings.
Guide to Install the Rinnai Controller
1. Turn Off Power to the Water Heater
As with any electrical work, safety is the first priority. Begin by turning off the power to your Rinnai tankless water heater by unplugging it or turning off the circuit breaker. This ensures there are no electrical hazards during installation.
2. Drill the holes
Remove the face plate of the controller to expose the screwing holes location, to mark and drill 2 holes for screws. If you’re mounting the controller on drywall, insert wall anchors for extra support. In the middle drill a hole for the wires to get the wires from the water heater unit to the controller.
3. Mount the Controller
Use a Phillips head screwdriver to attach the mounting screws to the wall. If you’re mounting the controller on drywall, first use a drill and insert wall anchors for extra support. Ensure that the unit is mounted level and at a comfortable height.
4. Connect the Controller to the Water Heater
- Remove the plastic screw covers: Begin by locating the two small plastic screw covers on each side of the front cover of your water heater. Gently pry them off to expose the screws underneath. These covers protect the screws and keep the front panel securely in place.
- Unscrew the front cover: Using a Phillips head screwdriver, remove the four screws (two on each side) that hold the front cover of the water heater. Be careful to keep the screws in a safe place, as you’ll need them to reattach the cover later.
- Take off the front cover: After removing the screws, carefully lift off the front cover of the water heater. Set it aside. This will reveal the internal components of the unit, including the PC board.
- Locate the PC Board: The PC board (Printed Circuit Board) is located in the lower right-hand corner of the water heater. This is where you’ll connect the controller, so take a moment to identify its location.
- Thread the controller cable: Take the cable from the controller and guide it through the grommet access hole found at the base of the water heater. This hole is designed to allow the cable to pass through the casing without damaging it.
- Lift the plastic cover on the PC board: The PC board has a transparent plastic cover to protect it from dust and debris. Gently lift this cover to access the controller connection points.
- Identify the connection point: Look for the specific port where the controller cable will connect to the PC board. This port is usually labeled for easy identification. Once located, connect the controller cable to the port and attach the field supplied wire by stripping its end and connecting it with the cable port. If there is no port on the PC board and has screw terminals labeled “TERMINALS FOR CONTROLS” you can directly strip the wire and connect it to the terminals.
5. Power On the Water Heater
Once the controller is connected and securely mounted, restore power to the water heater by plugging it back in or turning the circuit breaker on.
6. Set the Desired Temperature
After installation, the controller will display the current water temperature. You can now set the desired water temperature by using the up and down arrows on the controller. For most households, a setting of 120°F is ideal for safety and energy efficiency, but the temperature can be adjusted as needed.
7. Test the System
Once the controller is installed and the temperature is set, turn on a hot water tap to test the system. Verify that the controller is functioning correctly by observing the temperature display and making sure the water reaches the set temperature.
If you encounter any issues, refer to the error code display on the controller. The controller will show error codes that help identify problems with the water heater, such as insufficient gas supply, blockages, or temperature sensor issues. If your controller display is showing LC codes you need to perform maintenance, follow our guide “How to Flush Rinnai tankless water heater” to fix it.
