Rinnai Tankless Water Heater Reviews: 2020 Guide

What's better than an endless supply of hot water, especially in the cold winters? If you are in search of an on-demand tankless water heater, then what better manufacturer is there than Rinnai?

Rinnai is a Japanese company and the most reliable manufacturer of tankless water heaters out there. This company believes in bringing comfort and satisfaction to its customers. In this article, we have laid down a detailed review of some of the best-known Rinnai Tankless water heaters to help you find the perfect one!

When you are in need of a water heater replacement, looking for the right model for your home can be a real chore. No doubt you have heard of Rinnai tankless water heaters, and probably for good reason.

With extremely comprehensive and plentiful warranties and entirely replaceable parts, Rinnai is known for its longevity and durability. Its products display exceptional energy efficiency, while the rigorous testing ensures that all customers receive top quality products. If you’re wondering whether Rinnai tankless water heaters are the ones for you, take a look at this quick guide to the brand.

How Does Rinnai Compare to the Competition?

The term tankless water technology might be new for you; however, heaters based on this technology have been in use in Asia and Europe for decades now. Rinnai has continued to introduce some flawless appliances since its establishment in 1920. 

They are known for their top-notch technology and innovative ideas. Here, we’ve noted down some factors that make it stand out from its rivals. Let's discuss them one by one!

Space Saving

Rinnai is well-known for providing space-saving appliances. Whether you are looking for an indoor or an outdoor water heater, Rinnai is there to serve you. You can simply mount the appliance on the wall and get to enjoy a hot water bath.

You can easily save space and get a maximum of gallons per minute.

Efficient Performance

Unlike other storage style water tanks, Rinnai offers tankless water heaters that emit the least amount of CO2, making them environment-friendly. All of the products stand out in their efficient performance when compared to the competitors.

In fact, their least efficient model boasts 81% efficiency while the best one exhibits more than 92%, which is quite impressive.


All Rinnai products are backed by some amazing warranties, which make this brand one of the most reliable on the market. These warranties guarantee the reliability of the model, and the customer can use the appliance for many years without worrying about the expenditures for frequent replacements.

The Best of Rinnai Tankless

Rinnai Tankless heaters are dedicated to ensuring that their customers have the most comfortable experience. From compact models to quick-to-heat water, their products are designed to give a consistent performance that keeps their customers satisfied. Here are some of the things that give Rinnai Tankless such a great reputation:

Space Efficient 

Space can be valuable, especially if you live in an apartment or a smaller house. In this respect, you need a water heater that isn’t going to significantly reduce your living space. Rinnai Tankless water heaters are designed as compact wall-mounted devices that take up as ​little room as possible.

Not much bigger than a small suitcase, their wall-mounted tankless heaters can be installed both on the exterior and interior walls. Not only that, the smaller size means that water heaters can be installed in more creative places to save space, such as crawl spaces and small attics. This also means it can be installed in modular homes.

Replaceable Parts

Durability is key to ensuring the longevity of your water heater. However, this means the water heater is only as durable as its weakest part. With most water heater manufacturers, when a part breaks, you need to replace the whole water heater with a new model.

Rinnai boasts that its water heaters have replaceable parts that are easy to reinstall. This means that if a component breaks, you don’t have to spend a huge amount of money replacing the water heater. Instead, with replaceable parts straight from Rinnai, you are able to extend the lifetime of your water heater at a low cost. It’s great to know that every single part of a Rinnai water heater can be replaced by the company.


With a keen eye on the environment, Rinnai recognizes that customers want products that are kind to the Earth. By increasing energy efficiency and reducing emissions, Rinnai provides products that stick with this eco-friendly testament.

This is why you will see many of Rinnai’s products displaying the Energy Star seal. This gives Rinnai the merit for producing devices that far surpass the industry standards for energy efficiency. In fact, some of Rinnai’s products have outstanding energy efficient ratings of up to 93%, meaning only 7% of energy is lost. According to Rinnai, their products can reduce energy consumption levels by up to 40% while all reducing carbon dioxide emissions. In terms of eco-friendliness, this helps to reduce your carbon footprint noticeably.

Transitioned to UEF

Last year EF (energy factor) ratings were replaced with the new industry standard for energy efficiency measurements. The new ratings, UEF (universal energy factor) was expected to be adopted by all companies within the industry. Many brands have fallen short of this switchover, but Rinnai has taken the bull by the horns and jumped straight into this new measurement.

Where the EF only previously measured the fuel to heat efficiency rate, the UEF measurement now takes into account others factors and is better positioned to help consumers with selecting correct products based on how they use their hot water supply. While Rinnai’s products haven’t changed, they have taken the plunge to alter their ratings to this new measurement, showing their willingness to be ahead of the curve.

Recirculating Feature: Get Hot Water Quickly

Rinnai promises its customers that they no longer have to wait for hot water when they want to shower, as their products deliver immediate hot water all over the house. Using a re-circulation system to push the water through your plumbing system, hot water becomes available wherever it is needed, without delay.

Due to their dedicated return line installation, the pump pushes the water around the re-circulation system through this line and straight back to the heater. Due to this, Rinnai’s solutions can be installed with any plumbing configuration system already existing in your house. Normally, those households without a dedicated return line find that adding one is a very expensive endeavor. Rinnai, however, solved this issue with the re-circulation system, allowing rapid hot water without a dedicated return line.    

Quality Control Checks During Assembly

With a focus on technological quality and durability, Rinnai ensures that all products are of the best manufacturing level before they are sent out. Designed and engineered with intense precision, Rinnai products are put under extreme stress tests before being sent to the shop floor for consumer purchase.

Rinnai actually puts every product under five different staged quality control tests to ensure that every model is manufactured and assembled correctly so that Rinnai only sends out their highest standard products. On top of this, they have CSA-accredited laboratory technicians who give the products further testing for certification, development, application, and reliability. One of their two labs is dedicated to energy efficiency testing, while the other puts the products through their paces at commercial-grade application testing. All products meet an array of strict standards, including those set by the American National Standards Institute (AMNI).

Impressive Product Warranty Coverage

Rinnai has such a high level of confidence in every one of its products that it offers an outstanding warranty. The warranty is actually the best one available from any tankless water heater manufacturer. The warranty lasts for 12 years on the heat exchanger, 5 years on parts, and one year on labor. Not only that, if your device is registered within 30 days of purchasing the unit, you can register for extended coverage on labor.

When you consider the fact that all parts can be replaced, coupled with this lavish warranty, this really gives Rinnai the top spot for the longevity of products.


While Rinnai certainly looks to go the extra mile for their customers to receive great service, this comes at a price. Rinnai water heaters are quite expensive in comparison to their competitors’ equivalent models. Not only are the upfront costs of the water heaters expensive, but they are also very hard to install. This means that you need a professional installer, and the installation costs are also pricey, resulting in a significant finishing total.

Some customers also complained of limescale build up inside their Rinnai products. The LC code that indicates the presence of calcium was constantly on which demands the tank be serviced and cleaned. For the inexperienced user, this may add an extra cost to have someone come out, and deal with the buildup.

Available Rinnai Tankless Water Heater Models

Rinnai Tankless models are categorized by efficiency, labeled as High Efficiency, High-Efficiency Plus, Super High Efficiency, and Super High-Efficiency Plus. The V model catalog is their high-efficiency range, with a gallon per minute values ranging from 5.3 - 9.5 GPM on the varying models. The models, which come as either propane or gas-fueled, have a UEF of around 0.81 and are wifi capable.

The RL and RLX models are the high-efficiency plus run. They are re-circulation and wifi enabled, and have a UEF rating of up to 0.81. The units come with GPM ratings ranging from 7.5 - 9.8 and can come as either gas or propane fueled devices.

The RUCS and RUS range is categorized as super high-efficiency, with UEF ratings of up to 0.90. It gives these models the Energy Star seal. They are wifi enabled and come with a GPM rating of between 6.5 and 7.5 gallons per minute.

The super high-efficiency category is comprised of the RUR, RUC, and RU models. These have UEF ratings of up to 0.93 and are all Energy Star recognized. They are all re-circulation enabled, with RUR models having a 360 re-circulation pump. Available as both natural gas and propane models, these units come with gallons per minute values of between 9.8 and 11 GPM.

Comparison of the Best Rinnai Tankless Water Heater

If you are in a hurry, you are recommended to go through this brief comparison of the best Rinnai Tankless Water Heaters. This section discusses the comparison of some of the major specifications of tankless water heaters to simplify your search in addition to saving your time.

Model Name

Unit Size (L"xW"xH")

Energy Efficiency (SEER)

Home Sq. Ft.

Condenser Fan Motor

Cost of Unit Only

Installation Cost

Rinnai V Series HE






$600 - $1450

Rinnai RUC98iN






$1000 - $1500

Rinnai RUR98iN






$1500 - $1800

Rinnai RUC80iN






$1450 - $1700

Rinnai C199EN






$600 - $1000

Review of the Best Rinnai Tankless Water Heaters

Investing in a tankless water heater requires some research before making a purchase. Well, leave that to us. Here, we have drawn a detailed review of some of the best Rinnai tankless water heaters that we thought are worth the investment.

Rinnai V65IN Tankless Water Heater, Large, V65iN-Natural Gas/6.5 GPM


  • Offers a great supply of hot water
  • Comes with residential factory warranty
  • Exhibit a great design which is meant to last a long time
  • Mobile app lets you control the appliance from a distance
  • Energy-efficient model that can help you save on your bills


  • For indoor installation only
  • Might encounter a pressure drop
  • Not suitable for those on a tight budget

Our Review

Why it Stands Out to Us 

One of the finest models from Rinnai, this tankless hot water heater comes with a compact design that takes up very little space. It is built from high-quality materials to ensure the reliability of the product. Moreover, the best thing is the least emission of greenhouse gases like carbon dioxide. 

This model holds a 6.5 GPM capacity of hot water. The temperature can be set from 120 degrees F to the maximum 145 degrees F according to the choice of the consumer. Lastly, the product holds an impressive warranty, including 120 months for the heat exchanger, 12 months for the workmanship, and 60 months for multiple components of the appliance.

A natural gas powered water heater, the V65iN is installed inside and is 1.2” gas line compatible. It is wifi enabled and comes with a 10-year residential heat exchanger warranty, a 5-year warranty on parts, and a year’s warranty on labor.

Designed for a family home, this model produces 6.5 gallons per minute of hot water, making it a good model for the standard household single-family application. It has a BTU input of up 150,000 BTU and has anti-frost protection.

This model is quite energy efficient, with a UEF rating of 0.81, and an Energy Star seal which certifies this rating. It also has low NOx emissions and carbon emission, making it a safer and more eco-friendly model.

This unit comes with leak detection that will turn off the water if it suspects problems, which can prevent a great deal of property damage.

Bottom Line

With this model onboard, you get to enjoy hot water supply in a couple of seconds. Not only is the design impressive, but the appliance is great in functionality as well. The most striking feature is the mobile app that lets you control the performance of the heater even at a distance, enhancing the comfort level of the customer.

Moreover, the appliance is completely eco-friendly and energy-efficient as it works on natural gas. You might feel a little drop in the pressure when several showers are running, plus the installation of this model is limited to indoor use only. If you can overlook these factors, then this will be a great pick.

Rinnai RUC98iN

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe


  • No tension of gas leakage
  • Delivers hot water in very little time
  • Compact in size and takes less space
  • Model is quiet and efficient in its performance
  • Installation does not require too much struggle


  • Very expensive model
  • Lacks a re-circulation system
  • A slight drop in pressure if multiple showers are running

Our Review

Why it Stands Out to Us

This reliable model from Rinnai has a maximum BTU of 199,000, and the maximum energy rating is dictated as 0.92. Designed on the basis of low NOx technology, this appliance is great for reducing the emission of carbon dioxide. It is quiet and fast in operation and does not take long to provide hot water. Plus, it offers two venting options, including concentric PVC and twin pipe.

Talking about the design, it is established from high-end materials and tends to last for a long time. Plus, it is very compact and does not take much space, making it a perfect choice for indoor installation. Lastly, you get to enjoy a 12-year warranty on heat exchanger, 5-year on the various components, and a 1-year warranty on labor.

More suitable for larger applications, this natural gas-powered model can generate up to 9.8 gallons of hot water per minute. Extremely compact in size, this model can be installed inside in a little hideaway and has both a concentric of PVC venting option. The warranty on this model lasts for 12 years on the heat exchanger, 5 years on the parts, and a year on labor. This model is also wifi enabled and has a maximum BTU output of 199,000.

With a UEF factor of 0.92, this model is outstandingly efficient and also, therefore, heralds the Energy Star compliant seal. As well as its efficiency in fuel consumption, this unit has ultra-low NOx and carbon emissions, which significantly reduces your carbon footprint, showcasing this model as an eco-friendly device.

Bottom Line

An extraordinary model with a great set of features, this model is known for its superior performance. The design is extremely compact and requires little space for installation. In addition, it works on natural gas and, therefore, one of the energy-efficient models you will find on the market.

There would be no tension of greenhouse gas emission, thanks to the low NOx type design. Similarly, the appliance is backed by an impressive warranty that covers various parts of the appliance to ensure reliability. Moreover, the installation is a breeze, and since it does not take long to heat water, you will save quite a bit on water bills each month.

Best for the Money:
 Rinnai RUR98iN

Rinnai RUR98iN Ultra Series Condensing Indoor Natural Gas Tankless Water Heater, 9.8 Max


  • Package includes the insulation valves
  • Comes with 96% thermal efficiency rating
  • Offers two venting options to choose from
  • Exquisite design that goes with your interior
  • Built-in re-circulation system to provide endless hot water supply


  • Suitable for indoor use only
  • Installation might take longer
  • Does not include the venting kit

Our Review

Why it Stands Out to Us

Another efficient product from Rinnai, this model is immensely popular among the users for its attractive price tag and high-end performance. It comes with 9.8 GPM in order to deliver hot water all across your house. Being a condensing tankless water heater, this model is energy efficient and exhibits 98% thermal efficiency ratings.

Installation of this condensing model takes a longer than a non-condensing one, and you get to choose between concentric PVC or twin pipe venting kit. The most striking feature is its user-friendly design that is not only compact but gives you information about the whole system’s performance by merely looking at the LED display.

Bottom Line

A model packed with a set of exceptional features; this model is one of the most budget-friendly tankless water heaters you’ll find on the market. It is not only eco-friendly but user-friendly as well. It is extremely compact and can be installed indoors to offer hot water supply.

Additionally, it is WiFi compatible, and you can control the operations with the help of an app. The model is backed by a striking warranty of 12-year for the heat exchanger, followed by a 5-year warranty on multiple parts. Lastly, the model incorporates a re-circulation system that ensures an endless supply of hot water all across the house. What else can you ask for at such a price?

Best Rinnai Tankless Gas Water Heater:
Rinnai RUC80iN

Rinnai RUC80iN Ultra Series Natural Gas Tankless Water Heater, Concentric or Twin Pipe Installation


  • Two venting kit options to choose from
  • No tension of greenhouse gases emission
  • A great design that is user-friendly as well
  • Suitable for installation anywhere you want
  • Long warranty of 12-year to guarantee reliability


  • Relatively expensive model
  • Extra expenditure of venting kits
  • Might encounter a slight drop in the water pressure

Our Review

Why it Stands Out to Us

In case you are looking for a reliable tankless water heater that is not only compact in size but also includes some top-notch features, then you must get your hands on this model from Rinnai. It comes with a low NOx type design that ensures the reduction of greenhouse gases, especially carbon dioxide.

The maximum BTU is 152,000, and the energy rating reaches to 0.96. It offers a flow rate of 8 gallons of water per minute. It hardly produces any noise while working, plus the installation can be done both indoor and outdoor according to the requirements of the customer. Lastly, there are two venting options, including concentric PVC and dual PVC venting kits.

Bottom Line

This model is known for its quality, reliability, and durability. Extremely compact in design, this model can be installed both indoors and outdoors to deliver an endless supply of hot water. The thermal efficiency is great, plus it takes far less time to heat the water, which means you can cut short on your electric bills easily.

Talking about the warranty, manufacturers offer a long warranty of 12-year for the heat exchanger and another limited warranty for various parts of the heater. The flow rate is enough for delivering hot water all across the house, be it big or small. All the characteristics contribute to making this eco-friendly heater the best Rinnai heater on the market.

Best Rinnai Commercial Tankless Water Heater:
Rinnai C199EN

Rinnai C199EN Commercial Condensing Tankless Water Heater


  • Offers an endless supply of water
  • Multiple venting options to choose from
  • An energy-efficient model with a 96% rating
  • Suitable for both indoor and outdoor installation
  • Embodies a compact design with an appealing look


  • No batteries included
  • Frequent maintenance required for high-end performance
  • Relatively short warranty when compared to other models on the list

Our Review

Why it Stands Out to Us

The consumers of this product are quite satisfied with its performance, and therefore, this model is rated as the best Rinnai commercial tankless water heater. The model is highly durable and extremely compact in size, which enhances the location flexibility of the appliance. You can either install it indoor or outdoor according to your needs.

The maximum BTU is 199,000, and the energy efficiency goes up to 96%. In the package, you will find the isolation valves, and there are multiple venting options in order to enhance the installation flexibility of the model. Moreover, there is a limited warranty of 6 years on the heat exchanger to enhance the confidence of the customers in the product.

Bottom Line

In case you want a compact heater with installation flexibility, then you should definitely consider this commercial tankless water heater. Not only is the design compact, but there are various venting options in order to ease the installation process.

It works by condensing natural gas or propane. This appliance is capable of providing endless hot water supply all across your house. Moreover, the built-in WiFi capability helps the user to control the operation by merely sitting at a distance. Another striking quality is the least emission of the greenhouse gases, which makes it environment-friendly. Overall, the product boasts quality and reliability.

Rinnai V65EP Tankless Water Heater, Large, V65eP-Propane/6.5 GPM

Our Review

The V65EP model is fueled by propane and is installed outside. It is also ½” gas inch line compatible and is wifi-enabled. This model has the same warranty as above with 10 years for the heat exchanger, 5 years for parts, and 1 year for labor.  It has a 150,000 BTU maximum and heats water instantly, providing 6.5 gallons per minute.

A little less energy efficient than the above model, this water heater has an energy efficiency rating of 0.79 UEF. The temperature lock prevents accidental alterations on the temperature, which helps to increase energy efficiency when in use.

Regarding durability, this model has enhanced scale detection, censoring the buildup of limescale and helping users to troubleshoot this issue. It helps to keep the unit maintained, and prevents blockages and drops in efficiency.

What Kind of Warranty Does Rinnai Offer?

Rinnai is known to offer committed services to its consumers both in terms of reliability and quality. It offers multiple warranties on the product to enhance the overall experience of the customers. However, the warranty works only if the product is purchased from an authorized Rinnai dealer. Plus, you must have the receipt or any other proof of purchase in order to enjoy the customer services.

Mostly the products from Rinnai come with a limited warranty, which involves responsibility for damaged parts or any other defect in the product. Moreover, it will cover the services of workmanship when the appliance is installed according to the instruction manual provided by Rinnai. This warranty only holds for those appliances that are installed properly in the United States and Canada only. In case the appliance was not installed according to the guidelines of Rinnai, the warranty won’t work.

The warranty lasts for 10 years for the heat exchanger, plus other components are guaranteed for 5 years. The services offered by Rinnai will cover the repair or replacement of damaged parts or any other parts of the appliance. However, it may become void if the product is damaged by improper installation, poor handling, use, and operation.

Similarly, there will be no services provided if the model number or serial number has been vandalized.

Who is Rinnai?

Rinnai marks its position as one of the top international Japanese industries. It was founded in Japan a century ago in September 1920 by Hidejiro Naito and Kanekichi Hayashi. It was firstly named Rinnai & Co. and was totally based on the principles of harmony, truth, and spirit.

The fame of Rinnai expanded by virtue of its gas appliances in 1923. However, the company paused the distribution of these appliances for some time and started to manufacture aircraft parts. In 1958, the company made a partnership with Schwank GmbH, and from since then, it has been one of the finest companies working in gas appliances technology.

Tankless Water Heaters vs. Hot Water Tanks

Conventional water heaters come with big tanks that are known to be reliable. Installers and plumbers are more than familiar with how these systems work, and therefore have a sense of trust in a system that they know as straightforward. Due to this, the upfront costs of these kinds of water heaters and the installation costs tend to be relatively inexpensive, in comparison to tankless water heaters. In fact, many people can install them by themselves. Often argued to be inefficient in terms of energy consumption, technology has improved to the point that there are now Energy Star rated conventional water heaters.

However, on the flipside, conventional tank water heaters are always on, meaning that despite their energy efficiency rating, they will always be using energy to keep the water hot, whether needed or not. Equally, their big, bulky size is inconvenient in small spaces and often produces far too much hot water for the average family. Moreover, many people tend to inherit the space for a tank from the previous owners. This means they are limited to the capacity they can have, meaning they may not be able to meet their demand if they cannot fit a big enough tank in.

The big, bulky tanks also mean that installation is less versatile, as the tanks cannot be hidden so easily in smaller spaces. And as it cannot be placed outside the home, there has to be an area dedicated to it.

Tankless water heaters, in contrast, only work when someone needs hot water, heating the water on demand. This can reduce energy costs by around 25% or more per year. While only heating water on demand increases the energy efficiency of tankless water heaters, the models are far more energy efficient by their operational design than tank versions. Some tankless units can have UEF values as high as 0.93 compared to an efficient tank water heater with a UEF of 0.65.

Being small in size allows for more options when it comes to the installation of tankless water heaters. Despite their small size, if correctly fitted, tankless models will generate continuous instantaneous hot water all around the house to meet your demands. You will also find that the long warranties on tankless water heaters demonstrate the durability of the products, with some lasting up to 20 years.

However, tankless models are expensive to buy and have a more complicated installation. This means you often have to pay for a professional to put it in. It is not easy to retrofit a tankless model, and venting materials and labor can be pricey.

Rinnai Tankless Company History

Based in Nagoya, Japan, Rinnai began making products just under 100 years ago. First incorporated in 1920, Rinnai launched its first tankless water heater in 1921. The company went public in 1950 on the Tokyo Stock Exchange to expand its market. By 1967, they had consolidated their research and engineering to open a new technology center for innovation. In 1974, Rinnai established their US-based company Rinnai America Corporation, in Los Angeles.

By the early 2000s, Rinnai was improving its product range with a new tankless water heater in 2000 and a commercial version in 2001. This led to them being voted #1 as Builder Magazine's “Most Popular Product” for their LS Series Tankless Water Heaters in 2006.

In 2009, Rinnai narrowed down their focus to efficiency, and 6 products earned the Energy Star, with condensing tankless models being presented the following year.

Rinnai now has 20 branches around the world. Six of these branches are in Japan, with 86 sales offices across 15 countries, including Thailand, the UK, Vietnam, and the USA.


Winter is just around the corner. Therefore, it is better to do your homework and make sure to purchase the best water heater that completely fits your needs. Take your time to do your research about the perfect choice. Hopefully, this review has helped you enough in finding the model that you have been looking for.

Rinnai is an undoubtedly solid brand to put your confidence in when choosing a water heater. Make sure you understand your requirements when choosing a water heater for your household. A reliable and durable brand with an excellent warranty and a dedication to longevity, Rinnai products are a great choice. Just remember that upfront costs and installation can be a little pricey.

People Also Ask

Rinnai Tankless water heaters are used by a number of people, plus its superior performance has attracted certain new customers as well. Most of them have some queries about the functionalities. This section has summarized some of the frequently asked questions by customers in order to improve their overall experience with Rinnai Tankless water heaters.

Where is the Serial Number on the Rinnai Tankless Water Heater?

A serial number gives information about the manufacturing date as well as the age of the product. It is also known as the model number. You can easily find this number on the left side panel of any tankless water heater manufactured by Rinnai. Moreover, it gives details about the warranty of the model as well.

What Temperature Should I Set My Rinnai Tankless Water Heater?

Pressing the priority button gives a clear indication of the hot water supply. However, you can only adjust the temperature while there is no hot water running. Moreover, the temperature can be only set between 98 and 110 degrees F. You can do this by pressing the up or down button to reach the desired temperature.

What Does Priority Mean on Rinnai Tankless Water Heater?

You will find a priority button on the temperature controller. Pressing this button will light up a green priority light, which indicates that the controller is now responsible for controlling the temperature. From this indication, we get to know that tankless water heater is now ready to deliver hot water to the user.

Can a Tankless Water Heater Run Out of Hot Water?

No, a tankless water heater does not run out of hot water. In fact, one of the major advantages of using these heaters is that there is an unlimited supply of hot water. Moreover, you can enjoy a 5 hour-long shower without worrying about the supply of hot water. However, there is a limitation to the amount of water that can be supplied at a time.

What is Code 11 on a Rinnai?

Code 11 refers to the error code on Rinnai. Basically, this code is an indication of a lack of any built-in ignitions or gas supply to the whole system. These problems can be easily fixed by either checking the system for any loose or damaged part, or you can check the gas supply. Make sure it is turned on by turning on a gas appliance such as the stove.