Rinnai RUC98iN Tankless Water Heater Review

The Rinnai RUC98iN Ultra Series is one of the most energy efficient tankless water heaters on the market. Is it worth the investment? Find out in our review.

History of the Rinnai Corporation

When you are looking to make a big purchase such as a tankless water heater, we always advocate for researching the company who makes it. While Rinnai is a well-known company today, you may be surprised to discover that it once had humble origins in Japan. The Rinnai Corporation was co-founded in Japan in 1920 by Kanekichi Hayashi and Hidejiro Naito.

Even at its origin, the company always believed in manufacturing products ethically. During the late 1930s to mid-1940s, they manufactured many gas appliances for aircraft pieces as part of the war effort. During the 1950s, they partnered with Schwank GmbH, moving to the forefront of gas appliance innovation. Today, they are one of the leading producers of tankless water heaters, namely the Rinnai RUC98iN Tankless Water Heater and manufacture units for Bradford White.

rinnai-RUC98iN-tankless-water-heater-review - Rinnai RUC98iN

Rinnai RUC98iN Ultra Series Gas Tankless Water Heater

Efficiency
Ease of Use
Value
Features

Amazing Efficiency

This is one of the most energy efficient tankless water heaters around. It has an Energy Factor of .96 and is ENERGY STAR qualified. It is the only manufacturer to offer concentric and PVC venting options, which gives you the flexibility to install it in just the way you want. Advanced technology produces lower CO2 emissions, while NOx emissions are really low too. The catch is that you pay a bit more for the Rinnai name. Still, you can be assured of its quality.

Check Price
User Rating: Be the first one !

If you have been experiencing some problems with your water heater, it probably needs a replacement and it is about time that you look for a better performing one. Almost everyone is taking advantage of what technology can offer by transferring to a tankless water heater for their homes. If you are not very familiar with tankless water heating and the related products, then you can check out our guide to tankless systems. In this post we examine one of the best and most popular water heater models, while discussing the key features you should be looking for. 

How a Tankless Water Heater Works

To understand this specific product better, it is also important to know how tankless water heaters actually work. Most people are used to having a storage water tank heater and know that this type of heater keeps a huge amount of water inside a large tank, keeping it warm for whenever you or anyone in your family are ready to use hot water.

A tankless water heater, on the other hand, will only give water on demand. This means that it will only heat water up when you turn the hot water tap on. The water is heated through a process using propane, natural gas, or electricity. No water needs to be stored inside a tank as everything is done on demand. With this type of heater, the water can turn from cold to warm in just a few seconds.

The Main Benefits Of Tankless Water Heaters

Tankless (“on-demand” or “endless supply”) water heaters only heat water when the hot water faucet is turned on.  Tankless units most often use natural gas or propane rather than electricity, since it is more efficient to generate heat that way, and this separation from the electric grid means they are often added on the exterior of a building or structure for supplementary water heating. There are also electric tankless water heaters, though an electric heat exchanger typically can’t heat cold water as quickly as gas units. Plus they require a lot of electricity to run to support a sufficient temperature rise. But whether relying on a gas tankless or electric tankless system, the main benefit of instant water heaters is that they provide endless hot water while eliminating the extra cost of keeping 40 to 50 gallons of water hot in a storage tank, so you waste less energy. Because there is less need for constant heating and maintenance (such as prevention of scale build-up) of a large storage system, they also have longer lifespans than traditional water heaters with tanks. Condensing tankless water heater systems have an even higher efficiency rating, generating still more energy savings.

Difference Between Indoor And Outdoor Water Heaters

An indoor tankless water heater is installed inside a structure or building, whereas an outdoor tankless water heater unit is installed outside of the structure or building and is designed to withstand the elements. Outside units usually require less complicated installation than indoor units because air flow needs no special venting or piping  (tankless water heaters require specialized thermal exhaust handling, often concentric venting to provide oxygen while expelling exhaust). Indoor tankless water heaters also require a large amount of oxygen to ensure proper operation and a dedicated drainage system to eliminate condensation from the unit, whereas this step is less necessary with exterior units which can vent more directly. Installation of an outdoor model requires fewer adjustments needed for venting and plumbing and takes up no interior space inside the building. The location of external units can also be adjusted for efficiency in cases where local availability of hot water is important.

Tankless Hot Water Heaters vs Tank Storage Water Heaters

If you have done a little bit of research, you know that purchasing a water heater is a costly investment. When it is time to do some upgrades to your home or replace your old water heater, make sure you consider the cost and the scope of your budget. In this article, we will provide you with a thorough description of the Rinnai RUC98iN Tankless Water Heater as well as the pros and cons of both tankless water heaters and traditional ones. This way, you can make an informed decision. Before we dive into the product description and tech specs, we will give you a breakdown of what a tankless water heater is and why it is worth the investment.

What is a Tankless Water Heater?

Commonly known as on-demand water heaters, tankless water heaters use burners to heat water quickly as it passes through a heat exchanger. The water is directly delivered to your faucets and shower without being stored in a tank first. While tankless water heaters are typically powered by gas or electricity, tests by Consumer Reports showed they are twenty-two percent more energy efficient than traditional water heaters on average.

You may be wondering how traditional water heaters are different from tankless ones. Commonly found in homes, these insulated tanks hold somewhere between thirty to fifty gallons of water and store it until it is needed. When you turn your water on in the shower or at the sink faucet, the water runs from the storage area to the pipes until it is delivered in its destination. Storage water tanks can use either natural gas or electricity for their fuel source.

The Efficiency of Tankless Water Heaters

Homeowners that have tankless water heaters save so much in water usage and energy daily. Investing in a model like the Rinnai RUC98iN Tankless Water Heater will save you a lot of money in the long run. On average, this model has a 20 year + life in comparison to traditional storage tanks, which last anywhere between ten to fifteen years on average before breaking down.

What are the Pros and Cons of Using Tankless Water Heaters?

There is no such thing as a perfect product. To make sure you fully understand what you are investing in, you need to know what the pros and cons of tankless water heaters are.

Pros of Using a Tankless Water Heater

Using a tankless water heater saves you money over time. Energy.gov states that “For homes that use 41 gallons or less of hot water daily, demand (or tankless) water heaters can be 24% to 34% more energy efficient than conventional storage tank water heaters.” You will save over one hundred dollars per year on average.

  • They have a longer lifespan than traditional water heaters do. A tankless water heater can last twenty to thirty years in comparison to the ten to fifteen years of an average water heater.
  • Tankless water heaters can help with hard water filtering
  • They do not take up as much space as traditional water heaters do. They can easily be installed in tight quarters or even on outside walls if space is challenging for you.
  • You will have access to hot water whenever you need to.
  • Tankless water heaters have the ability to deliver two to three gallons of hot water per minute. You will never have to stand and wait for your shower water to warm up.

Cons of Using a Tankless Water Heater

  • There is often a high up-front cost associated with purchasing a tankless water heater.
  • The up-front cost of purchasing and installing a tankless water heater is around $2,000 – $4,500 as opposed to $500 to $800.
  • When you choose a tankless water heater to replace your traditional storage heater, your plumber will need to take time to install it. This increases the overall cost; you may need to relocate existing piping.
  • Washing laundry and taking a shower the same time might be too much for your tankless water heater to keep up with. If you have multiple uses for hot water in your home, you may need to invest in a tankless water heater.

What are the Pros and Cons of Using Traditional Storage Tank Water Heaters?

In this section, we address the pros and cons of using traditional water tank heaters.

Pros of Using a Traditional Storage Tank Water Heater

  • Traditional storage tank water heaters are significantly cheaper when it comes to upfront costs. Instead of spending $2,000 – $4,500 to purchase and install a tankless water heater, it will only cost you between $500 to $800 to purchase and install a traditional storage tank.
  • They are simpler to operate and handle than tankless water heaters, particularly when it comes to maintenance and repairs.

Cons of Using a Traditional Storage Tank Water Heater

  • Utility bills are often higher than when busing a tankless water heater. Investing in a tankless water heater will save you on energy bills in the long run.
  • You will often have to wait for your shower or sink water to warm up. Remember that your water is being stored in a tank and will have to travel through pipes before it reaches the destination. If you need to wait for your water to warm up, this will increase your utility bills.
  • Traditional storage water heaters take up much more space than tankless ones do. If the space in your home is already limited, this can be frustrating. They cannot be stored outside of your home.
  • If you are the last person in your household to take a shower, the water will often be cold.
  • You may need to invest in a larger heater if you have a large household. While this may relieve your shortage of hot water, your energy bills will increase. The average traditional water storage tank can only support three warm showers in a row.
  • Traditional storage tank water heaters need to be replaced every ten to fifteen years, whereas a tankless water heater only needs to be replaced every twenty + years. This means you will need to install them nearly twice as often.

Can your bank account handle the high initial cost of a tankless water heater? Before you make a big purchase, consider the upfront cost and your budget limitations. If you can afford it, making the purchase is worthwhile. You will save a lot of money in the long run by choosing a tankless heater. However, for those of you who are on a fixed income, purchasing a storage tank water heater may make more sense. Discuss the different types of water heaters with your plumber to weigh your options.

Why Do Tankless Water Heaters Need Maintenance?

As we previously mentioned, tankless water heaters can last for over twenty years but only if they are properly maintained. Unfortunately, they are often inaccurately marked as low maintenance. This could not be further from the truth. There is a large difference in how much maintenance the two types of water heaters actually require. Hard water affects both types of heaters.

Hard water refers to how much minerals your water supply carries in it, particularly magnesium and calcium. These minerals can build up in a tankless water heater quickly, often plugging up passages where water can no longer flow. This causes your heater to have to work that much harder in order to warm your water supply. Over time, this strain reduces your heater’s lifespan and raises your electricity bills. Mineral buildup in your home appliances often causes irreparable damage and may require an entire heating unit to be replaced. Unfortunately, a manufacturer’s warranty does not cover this type of damage.

During routine maintenance, a professional will descale (or de-lime) your tankless water heater and remove any accumulated buildup around the essential heating parts. You should have a professional check in to descale your tankless water heater at least once per year. However, you may need additional maintenance if you live in an area with high hard water levels. No matter where you are located, water in your heating system will have minerals in it. However, there are some areas of the country where water is much harder. Have your municipal water supply tested to determine if you need additional water heater maintenance checks.

About The Rinnai RUC98iN Ultra Series Gas Tankless Water Heater

Now that you know all of the pros and cons of using a tankless water heater, it is time to learn about the Rinnai RUC98iN Tankless Water Heater. This device is an indoor gas tankless water heater designed for residential and commercial application. It uses propane or natural gas and comes with various venting options. One of our favorite features about the Rinnai RUC98iN is its compact design. Homeowners with limited space will appreciate that it does not take up much space. The dimensions are 26 inches in height, 10 inches and thickness, and a weight of 61.7 pounds. We recognize that while the body is sleek, it is not a lightweight heater.

Taking a look at the design, you will see a gray exterior with controls located on the lower front panel. There is a power button, water temperature control, gas buttons, and a digital display screen. You can control the temperature of the water and lock the temperature to prevent unauthorized access. When it comes to venting options, there are concentric and twin-pipe PVC features. The Rinnai RUC98iN Tankless Water Heater complies with nitrogen oxide emission standards.

Besides its compact design, this is one of the most efficient and eco-friendly tankless water heaters we have found on the market. Using an electric ignition system, it only uses 2 watts of energy in standby mode and up to 64 watts while actively working. In winter, it may require up to 146 watts to prevent water from freezing. As one of the most powerful home units, it has an energy factor of 0.95 with either gas or propane. While this is a higher-than-average number for gas-powered home water heaters, it is also Energy-Star certified. The flow rate is wide and it has a minimum gpm activation rate. The numbers indicate that the Rinnai tankless water heater can power up multiple faucets and showerheads and can be used in multiple bathrooms without interruption of hot water flow.

The Rinnai RUC98iN Tankless Water Heater can heat your water between 90 to 140 degrees Fahrenheit on average. The hottest recorded temperature it filtered is 185 degrees Fahrenheit. One of the downsides we have to mention though is that it is expensive and uses a 0.75-inch MNPT connection rather than the standard half-inch connection that most homes have. In addition, it can be difficult to install and requires maintenance by its company personnel so you won’t void its warranty. With this said, many of its competitor brands have similar warranty restrictions.


About The Rinnai RUC98iN Ultra Series Gas Tankless Water Heater

The RUC98iN gas tankless water heater was manufactured by Rinnai, who is one of the industry’s benchmark companies. They have been in the business for 45 years, and are known to deliver high quality and innovative water heating and home heating appliances for both residential and commercial use. They also provide and stand by a limited warranty on almost all of their products.

This Rinnai tankless water heater reviews really well on sites like Amazon where it has an average rating of 4.6 stars.


Product Features

  • The Rinnai RUC98iN is an indoor gas tankless water heater which uses propane or natural gas and has either concentric or twin pipe PVC venting options.
  • It complies with nitrogen oxide emission standards.
  • It stands 26 inches tall and weighs 61.7 pounds, roughly the size of a largish carry-on suitcase. But although it is compact and has a sleek design, this hot water heater is not lightweight at all. But, even if it’s quite heavy, the space-saving and sleek design and built-in concentric style vent outlets allow it to be installed almost anywhere in the house.
  • The exterior is gunmetal gray where the controls can also be found, specifically on the lower portion of the front panel. The controls include a power button, gas control, and water temperature buttons, as well as a digital display.
  • It allows control of the temperature of the hot water coming out and you can even lock the temperature button to prevent unauthorized access. That way, you will be ensured that the water temperature will always be constant and will not be too hot for children or the elderly.
  • The Rinnai RUC98iN has bigger inlets and outlets than most gas tankless water heaters and is also bigger and heavier but more powerful too. It has an energy factor of 0.95 which is higher than the average for water heaters powered by gas.
  • It can supply sufficient hot water to multiple showers and faucets in a house with several bathrooms and there will be no interruption to the flow of hot water. This can be attributed to the fact that this heater has a minimum to maximum gas burn rate varying from 15,200 to 199,000 BTU which is considered to be a very wide range. The Rinnai RUC98iN’s hot water flow rate range is also wide at 0.26 to 9.8 gallons per minute, while the minimum activation flow rate is only 0.4 gallons per minute.
  • The Rinnai RUC98iN is capable of heating water from any temperature to 95 to 140 degrees Fahrenheit and in fact, the commercial model has the capacity to provide water as hot as 185 degrees Fahrenheit. This is an excellent temperature range for a unit of this size.

Pros and Cons

Here are some of the benefits that the Rinnai RUC98iN tankless water heater offers:

  • The unit does not need a lot of space so you will have more space at home, which can be used for other purposes.
  • It is Energy Star certified, and environmentally beneficial because of its energy efficiency ratings. It saves energy by heating water only when needed.
  • The Rinnai RUC98iN also helps in the reduction of electricity consumption and saves a considerable amount of water.
  • It is quiet and does not make any distracting sound.
  • Since it is tankless and does not store water, there are lesser chances of getting any kind of unwanted residue from the faucets or shower heads. This makes this heater a cleaner alternative. The water is not stored in a metal tank that can build up scale and rust, which can eventually pollute the water that you use for bathing, brushing your teeth, cleaning, and even cooking.
  • Hot water supply is unlimited and there is no waiting time, unlike a conventional water heater. The latter needs to heat more water once the supply has been used up and that may take a while. However, there are also things which some people did not like and could have been better on the RUC98iN:
  • The price is a bit higher than most gas tankless water heaters available in the market.
  • It is bulkier than most tankless water heaters. Though when compared to a traditional tank based system it is very small.
  • The Rinnai RUC98iN is quite difficult to install and even requires maintenance to be conducted by a repair personnel certified by Rinnai. This is essential so as not to avoid warranty. Take note that the installation process may require a significant amount of money since it has to be conducted by a certified professional.

Rinnai Tankless Water Heater — Frequently Asked Questions

Are you interested in purchasing the Rinnai RUC98iN Tankless Water Heater? We have listed the most frequently asked questions about this device and provided detailed answers below.

What Are its Power Supply Requirements?

Standard Rinnai tankless water heaters need 120 volts AC, 60 Hz, and fewer than three amps.

How Does Self Installation Work with the Rinnai RUC98iN Tankless Water Heater?

You will most likely need to pay for a professional service for your Rinnai installation. Improperly installing a gas appliance can be extremely dangerous and pose a number of risks to both your family and your property. Rinnai highly recommends that all of their products be installed by one of their company’s trained and licensed contractors or an approved and qualified plumber according to federal, state, and local regulations. Remember that improper installation of a Rinnai product can affect your company warranty policy.

What is the Average Cost of a Rinnai Tankless Water Heater?

Suggested prices for a Rinnai tankless water heater span between $900 to $1,995 depending on the model. This does not include installation and venting costs. For an accurate cost estimate, contact your local Rinnai dealer.

Can the Rinnai RUC98iN Tankless Water Heater be used on RVs and Houseboats or for a Pool and Spa?

Do not attempt to use the Rinnai RUC98iN Tankless Water Heater for RVs and Houseboats or for pools and spas. The chemicals from the pools and spas would damage the heating unit.

How Long will the Rinnai RUC98iN Tankless Water Heater Last?

The average life expectancy of the Rinnai RUC98iN Tankless Water Heater is 20 years. However, its actual performance will depend on a number of factors including how often maintenance is performed, water quality (aka hard water vs soft water), usage rates, the condition of its environment, and more.

What Does Temperature Rise Refer to?

This term refers to the maximum flow rate of tankless water heaters. The temperature rise is quite literally the difference between the unit’s set temperature and that of the incoming groundwater. For example, if you set the temperature to 120 degrees Fahrenheit and the incoming water is only 60 degrees Fahrenheit, this is 60-degree temperature rise. The lower you set the temperature and the hotter the incoming water is, the more hot water your unit can produce. If it is sized correctly, your unit should not have a problem producing enough hot water for your needs.

Can You Use a Rinnai External Tankless Water Heater in Cold Climates?

Rinnai external tankless water heaters can be used in cold climates. The unit offers freeze protection for the unit down to negative thirty degrees Fahrenheit. You just need to make sure you have power and gas for the appliance. In addition, trace and insulate your heat pipes to protect them. Rinnai recommends that you install an optional drain system on units installed in outdoors and cold climates. If installed, these systems will allow the water inside of your unit to drain out in the event of a power or gas outage.

Do Rinnai Tankless Water Heaters offer a UL Rating? Do They Manufacture an Electric Tankless Water Heater?

While the Rinnai tankless water heaters are not UL certified, they are certified by CSA International to ANSI Z21.10.3 Standard Gas Water Heaters. They do not make an electric model for two reasons. The first reason is that the power requirements of an electric unit large enough for hot water generation are prohibitive. Second, the operation cost of an electric tankless model is much higher than that of natural gas. Nation averages show that electricity costs twice as much per BTU as natural gas does.

Does Rinnai Have a Backup Battery System? Can it Be Installed in a Mobile Home?

Rinnai does not offer a backup battery system. Check with your local retail store to find an uninterrupted power supply system (UPS) that matches your needs.  They do offer units certified for mobile home installation. They are included as a part of the company’s VB series and include qualifying V53e models too.

What is the Cold Water Sandwich Effect?

This phrase is used to describe the introduction of cold water into a hot water supply line. The cold water sandwich effect occurs during frequent on and off operation of an instantaneous water heater. When present, it creates a temporary drop in temperature as it is discharged from your shower, tub, or faucet. This phenomenon frequently occurs with the operation of most tankless water heaters but is minimized with Rinnai heaters.

How do Rinnai water heaters minimize the cold water sandwich effect? Since they are controlled by microprocessors, when water flow through them stops, they remain in a ready state for one minute. If the water flow through the heater begins within one minute after the water stoppage, the heater backfires within one to two seconds. This reduces the cold water sandwich effect that low tech tankless water heaters and traditional heaters have. Safety standards developed require a delay in the ignition sequence of every type of gas water heater.

It is nearly impossible to eliminate the cold water sandwich effect from standard plumbing systems. With this said, it can be eliminated from plumbing systems with a good circulating system. Rinnai has two proven effective methods to curb the cold water sandwich effect in residential circulating systems. The first method uses a small electric water heater for a dual purpose. This heater offsets the heating losses from the hot water circulatory system. Next, the system utilizes a small storage tank on the outlet of the Rinnai heater. It eliminates the cold water sandwich effect at its fixtures.

What are the Main Reasons Why You Should Invest in a Tankless Water Heater?

  • Save money in the long run on utility bills
  • Continuous hot water supply
  • It’s a space-saver for your home
  • Tankless water heaters have a long lifespan (often 20 years +)
  • They are eco-friendly

What Type of Gas Line Does a Rinnai Tankless Water Heater Use?

As we previously mentioned, the gas connection unit for the Rinnai tankless water heater is a 0.75-inch MNPT. The gas supply needs to be sized to handle all of your appliances. Hire a professional for all gas line sizing and installations. Rinnai recommends contacting your gas provider to get an accurate reading.

Can You Convert a Rinnai Tankless Water Heater to a Different Gas Type?

Rinnai offers a field conversion program. Kits to convert from natural has to propane (or vice versa) are available for most of their tankless water heater models. Have your installation or service provider call 1-800-621-9419 to make sure your model qualifies. You can obtain a step by step instruction kit for the conversion process. These kits are shipped directly from Rinnai only after your service provider has spoken with Rinnai’s technical support. Conversion kits are only approved for non-sold inventory and/or mobile homes.

Frequently Asked Questions of Tankless Water Heater Owners

Are you already an owner of a tankless water heater? Read on to find some of the top FAQs and answers.

Why Does the Fan Keep Running Even After Turn off the Hot Water?

The fan continues to run after you turn off the hot water temperature during rapid starting and stopping.

White Smoke is Coming out of the Exhaust. What Does This Mean?

During cold weather, the exhaust coming from your tankless water heater is hotter than the outside air. When the exhaust fumes condense, they produce water vapor. It is nothing to be concerned about.

I Don’t Have any Hot Water When I Open up the Tap. Why?

Make sure your power and gas are turned on. You need to have gs, water, and electricity connected to your tankless water heater.

Does a Rinnai Tankless Water Heater Have a Standing Pilot?

No. There is no direct electric ignition.

There is a Long Wait Time to Get Hot Water. What is Going On?

How long you wait for hot water directly correlates to the distance between the water heater and the point of use. The Rinnai produces hot water a few seconds after it starts. However, you must first get all of the cold water out of your pipes. To give you an example, if your kitchen sink is fifty feet away from the water source and the flow rate is one gallon per minute, it will take about ninety seconds for hot water to reach your kitchen sink. We all hate having to wait for hot water. The placement of your hot water tank makes all of the difference. Try adding a small hot water tank to the circulating side of your Rinnai tankless water heater with a recirculating loop. This will heat all of the water without shortening the lifespan of your device or impacting the warranty.

What Type of Maintenance Does the Rinnai RUC98iN Tankless Water Heater Require?

There are two types of maintenance that your technician should perform to keep your tankless water heater running smoothly. The first is to check your in-screen filter for debris. When you do this, make sure that your water filter is turned off. Located the inlet fixture by the cabinet and unscrew the plug to remove it. Expect some water drain. Second, flush the unit out periodically between draining. This will keep your unit free of scale and lime deposit buildup.


Final Review of the Rinnai RUC98iN

With an unlimited supply of hot water, savings in the energy and water consumption, great space-saving design, and environmental benefits, it is hard to say no to this product. As indicated, there are many features that would make you want to move from a conventional water heater to a tankless one. Just make sure that you consider the potential issues that were mentioned earlier. If you think that those will not be of major concern, then this might be the perfect choice for you and your family.


Check back soon for more Rinnai tankless water heater reviews.

Hard water is a particular pest to water heaters as it builds up scale on the fixtures like the heating element. This affects the lifespan of the appliance. Check out our guide to water softeners to find out more about these products that prevent scale build up.

We will be happy to hear your thoughts

Leave a reply