Nothing is more annoying than going through the hassle of installing a tankless water heater only to realize it doesn't get hot enough for your household.
The default temperature for most Rinnai units is 120°F, and they can be increased to a high of 140°F.
The first steps of adjusting the Rinnai temperature is to turn on the power and remove the front panel of the heater. The majority of Rinnai tankless heaters can be adjusted by flipping a dip switch or using a front button procedure. However, you may need to consult the manual for your specific model.
6 Steps For Rinnai Temperature Adjustments
Step 1 - Turn Power On
In order to adjust the default temperature on a Rinnai unit, the power has to be on.
You will need to modify a dip switch but you will also be pressing buttons on the unit, so the power has to be active.
Step 2 - Remove Front Panel
The first step to changing the default max temperature on a Rinnai tankless heater is to remove the front panel.
There are two plastic trim sections on each side of the water heater that you can slide out. Once the trim pieces are removed, the screw heads are exposed. You can remove the four screws with a screwdriver or electric drill.
Carefully remove the front panel.
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Step 3 - Press Priority Button
The priority button needs to be green and glowing.
If not, press the priority button.
Step 4 - Flip Switch #6 in Dip Switch SW1
Take a look at the dip switches inside the Rinnai tankless heater, these are the tiny switches in series connected to a circuit board.
With A Temperature Controller
If your Rinnai tankless heater has a temperature controller (up/down arrows to change the temperature), then there is a particular switch to flip.
To adjust the max temp to 140F (rather than 120F), you will have to flip switch #6 in the dip switch SW1.
Dip switch SW1 is the row of tan-colored switches inside the heater. You must flip the switch #6.
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Without A Temperature Controller
If your Rinnai tankless heater doesn't have a temperature controller, then there will only be two temperature settings—the default 120F and the max 140F.
To change the temperature setting to 140F, you will have to flip switch #5 (rather than #6) in the SW1 dip switch (tan-colored switches).
Step 5 - Verify Temperature Change
If you have a temperature controller, you simply hit the up arrow to see if you can get to a higher temperature, and to verify that the dip switch worked.
If you don't have a temperature controller, you can open up a faucet and see if you get a higher temperature.
Step 6 - Install Front Panel
After you have changed the default temperature setting, and verified the change, you can now re-install the front panel.
Simply put back in the four screws, and slide the two plastic trim pieces onto the side.
Safety Issues With Raising Max Temperature
Always be careful when adjusting hot water temperatures in a household, especially if you have small children. Scalding can occur in just three seconds at a water temperature of 140F.
If your Rinnai tankless water heater doesn't have a temperature controller, and you have small children, the CDC recommends keeping it at the default 120 degrees Fahrenheit or lower.
If you have a temperature controller, you can adjust it anywhere from 120F and up but below the maximum temp of 140F after raising the default.
Not Enough Hot Water
And after raising the default, if you aren't getting enough hot water, you may want to lower the temperature a bit.
If you lower the temperature to what you actually use at the faucet, then you won't need to mix in as much cold water at the faucet, and you will get more hot water.
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