How To Use Rinnai Tankless Water Heater [Detailed guide]

A detailed Guide on how to use your Rinnai Tankless Water Heater. Learn Step-by-Step Operation, Temperature Control, and Safety Tips for Optimal Performance.

Before we dive into how to use or turn ON Rinnai tankless water heater, let’s start with the basics. Your Rinnai Tankless Water Heater is a marvel of modern technology designed to provide endless hot water on demand. Unlike traditional water heaters that store and constantly reheat water, tankless units instantly heat water as it flows through them, delivering hot water whenever you need it.

Installation Made Easy

If you’ve already installed your Rinnai Tankless Water Heater, congratulations! You’re one step closer to a more efficient and luxurious way of life. If not, don’t worry – Rinnai offers professional installation services to ensure your unit is set up correctly and safely ask for installation and its cost at the time of purchasing the unit. Once your tankless water heater is installed, you’re ready to embark on your journey to hot water bliss.

Understanding the Technology

Once your Rinnai Tankless Water Heater has been professionally installed, it’s time to learn how to use its innovative technology for consistent, reliable, and safe hot water supply for longer years. These tankless heaters are equipped with high end features operated by a small computer chip which monitors and ensures on-demand hot water delivery at given temperatures by maintaining safety features.

rinnai tankless water heater outer parts classification rur 199

Best thing about this tankless water is its Rinnai’s intelligent modulation system, which adjusts water flow to maintain a consistent water temperature, compensating for variations in incoming water temperature during seasonal changes. The modulating gas valve further enhances efficiency by regulating heater output based on demand and desired temperature.

Key Components and Functions

  • Ignition System: Rinnai tankless units employ direct electronic ignition, eliminating the need for a pilot light. This means the unit automatically ignites the burner when hot water is required.
  • Venting: These units use direct venting, drawing combustion air from outside and expelling flue gases outdoors.
  • Manual Gas Valve: While installation a manual gas valve is installed on the gas line which is located near the water heater, it should be fully turned ON by turning the knob parallel to the pipeline.
  • Isolation Valves: The included isolation valves must be installed on both hot and cold water lines to help us to block the water to the system and to the faucets while performing maintenance like draining and flushing Rinnai tankless water heater.turn off and isolate rinnai tankless water heater
  • Water Flow: To initiate the heating process, open a hot water tap with a flow rate higher than the minimum requirement (0.4 GPM) and allow time for hot water to reach the fixture. Adequate water pressure (50-150 PSI) is essential for optimal performance. The time taken for hot water to reach fixture depends on the distance between the tap and the heater unit.

How to turn ON Rinnai tankless water heater and how to use its temperature controller

Turning ON Rinnai Tankless Water Heater is an easy process. Here’s a step-by-step guide to help you get started:

  1. Locate the Temperature Controller: Find the temperature controller on your Rinnai Tankless Water Heater. It’s typically integrated into the front of the unit for indoor models, while it’s provided separately for outdoor models. Please note that the Series V53 does not come with a temperature controller.locating the temperature controller and it buttons of rinnai tankless water heater
  2. Power On the unit: Use the ON/OFF button on the controller to power on the unit. The temperature controller will light up and show the default temperature on the display, indicating that it’s ready for use.
  3. Set the Desired Temperature: The temperature controller allows you to easily adjust the water temperature to your preference. For indoor models, you’ll have an LCD display and several buttons on the control panel. Use the up and down arrow buttons to increase or decrease the temperature setting, which can be displayed in both Fahrenheit and Celsius, by default it will be in Farenheit which you can change according to your preference.
  4. Priority Mode: If you want the temperature controller to take charge of regulating the water temperature, press the “Priority” button. When you press it a green led is lit beside the button, it indicates that the controller is actively managing the temperature, by providing consistent and comfortable hot water supply.
  5. Default Temperature Setting: Rinnai water heaters are factory-set to a default temperature, usually around 120-125°F (approximately 48-52°C). You can adjust this setting to suit your preferences using the temperature controller.
  6. Higher Temperature Options: In certain cases, such as commercial applications, you might need hotter water. Rinnai offers an alternative temperature controller (MCC-91-2) that allows for higher temperatures, up to 185°F (approximately 85°C). This option is available for specific needs and requires professional installation and attention while using.
  7. Diagnostic Codes: The advanced technology of Rinnai water heaters also includes a diagnostic system. If there’s an issue with the unit, it will display an error code on the temperature controller’s LCD screen. This feature makes us easy to understand the problem while troubleshooting and maintenance.
  8. Safety Considerations: Keep safety in mind when adjusting temperatures. Water above 125°F (approximately 52°C) can pose risks, particularly for children and seniors.

Helpful article: Rinnai tankless water heater maintenance: Clean and Descale

Safety Tips to remember before using your Rinnai Tankless Water Heater

Before you start enjoying the benefits of your Rinnai Tankless Water Heater, it’s crucial to prioritize safety. Keep note of these important safety guidelines in mind to to keep your water heater unit worry-free and secure operation. Neglecting and not following the safety measures can lead to damage in property, personal injuries and may even cause more serious issues.

  1. Automatic Ignition Only: Unlike traditional water heaters, your Rinnai tankless unit doesn’t require manual lighting. It comes equipped with an automatic ignition device that handles the ignition process. Avoid attempting to ignite the burner manually; let the unit do its job.
  2. Gas Detection Precautions: Before you begin operating the water heater, take a moment to detect any gas odors around the unit’s vicinity. Since some gases are heavier than air, it’s important to smell near the floor as well. If you detect a gas odor, follow these steps:
    • Refrain from using any appliances or lighting anything in your home.
    • Do not touch any electrical switches, and avoid using your phone indoors.
    • Use a neighbor’s phone to immediately contact your gas supplier.
    • If you’re unable to reach the gas supplier, call the fire department for assistance.
  3. Manual Gas Valve Handling: When dealing with the manual gas control valve, always use your hand to turn it. Do not attempt to use any tools for this task. If you find it difficult to turn the gas valve by hand, it’s best to seek help from a certified technician instead of attempting repairs yourself.
  4. Avoid Water Contact: Never operate the tankless water heater if any part of the unit becomes submerged in water. If the unit does come into contact with water, it’s important to have a qualified plumber inspect and address the situation to resolve any potential issues.

Safety should always be a top priority when operating your Rinnai Tankless Water Heater. In our upcoming articles we will let you learn about the error codes of Rinnai tankless water heaters, so please stay tuned. If you have any doubts please comment below, we are ready to answer every question you ask. Browse through our articles for more helpful content on Water heaters.

TanklessHelp Staff

TanklessHelp Staff has an experienced writers and researchers in the field of water heating technology. With a background in HVAC and plumbing, Tanklesshelp staff has in-depth knowledge in many types of waterheaters in America and Canada. They have a passion for educating homeowners and businesses on solving easy to hard repairs and guide them on how to maintain them to save money.

Related Articles


  1. Can you open the cold water on the shower to change the water temperature? Or if you do that, the heater will turn off because you are decreasing the hot water flow?

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button