Two Rinnai Tankless Water Heaters

How to Adjust the Temperature On a Rinnai Tankless Water Heater

You don’t need to be rocket science to know that hot water may be harmful, especially when it comes to newborns, children, older persons, and people recovering from surgeries. When you set the thermostat too high, the risk for hot water scald is essential, and you should never underestimate it.

Why is hot water dangerous for us?

It may sound surprising, but it doesn’t take high temperatures for burns to occur. Here are some situations that cause first-degree injuries:

  • Exposure to 140F degrees for just three seconds
  • Eight minutes of exposure at 120F degrees
  • Water with 130F degrees can cause burns when touching the skin for 20 seconds

Safety should never undermine when it comes to using hot water with children. For example, you should always verify the temperature of the water before bathing or showering a child. Also, you must never leave a child/infirm person in the bath without any supervision.

You should always check the temperature before trying the bathe a newborn or a child.

What’s the best way to set the temperature on your Rinnai tankless water heater?

Even if there are many models of Rinnai tankless water heaters, adjusting the temperature is quite similar between models.

  1. When your heater is off, you need to press the On/Off button for turning it on. You can also change “Priority” when the hot water isn’t running.
  2. Continue with pressing the “Priority button” on your temperature controller. You will notice the green Priority light glowing. It’s nothing to worry about; the light informs you that the controller is managing the temperature and that your unit can heat the water.
  3. Press the ▲ or ▼ buttons to get to the temperature you planned to have. Every hot water source in the house (connected to the water heater) will be able to give water at the set temperature until you make any other changes to the setting.

Some important notice to consider

there are several aspects to pay attention to when adjusting or using your Rinnai tankless water heater:

  • When the unit gives hot water, you may change the temperature only between 98 and 110F degrees.
  • If you’re using the Rinnai unit in daycare centers, schools, nursing homes, or other commercial applications, you have to check the local codes for the maximum water temperature that is allowed.
  • Should you use a unit that comes with a remote controller, keep in mind that it’s going to return to the default setting (104F degrees) when not used for more than six hours.
  • Some variations between temperature showed on the remote controller and the temp at the tap may develop. The length of the pipe to the water heater and the weather conditions can be the most significant reasons.

The Rinnai tankless water heaters will give hot water at the set temperature even if the water flow isn’t continuous or when you’re using more than one tap at a time.

Are the adjustments different when using a controller?

Some models require an older controller (MC-45), and you need to move dip switch No.6 in the bank of 6 dip switches so that it’s ON. The temperature settings may vary.

There are also Rinnai units that have a maximum temperature of 120F degrees, but you can raise the temp to 140F degrees. The temperature settings vary from 125 to 140F degrees, and you can do it by adjusting dip switch 6 to ON in the SW1 bank of 8 dip switches.

When your application needs higher than 140F degrees, you have to install a mixing valve to moderate the temperature to 140F degrees.

Here are the temperatures to have in the home:

  • Shower- 98-110F degrees
  • Bath fill- 102-110F degrees
  • Kitchen -120F degrees

Let’s not forget that you can also switch from Celsius to Fahrenheit and the other way around. It’s enough to push and hold the “On/Off” button for 5 seconds. Also, make sure that the water heater is Off.

Some Rinnai units feature an MCC-91 controller. It’s a breeze to obtain high temperatures when using the connected controller. We need to highlight that the MCC-91 is designed for commercial and hydronic applications. Should you use it for residential dwelling for the Hydronics application, you need to install a mixing valve so that you control the potable hot water temp at the appropriate value.

Can you adjust the temperature without a controller?

The default temperature setting for some models that don’t include a controller is 120F degrees. If you want, you can go with 140F degrees by merely adjusting the dip switch. You should adjust the dip switch 5 to on in the SW1 bank of 8dip switches. Adjust the dip switch 5 to OFF for obtaining 120F degrees water temperature. Should you also decide to install a temperature controller, the dip switch, five will not affect the temperature adjustments.

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