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Rinnai Ruc98in Ultra Series Review

Product At A Glance!!

Rinnai RUR98iN 9.8 Max GPM Ultra Series Condensing Indoor Natural Gas Tankless Water Heater with Recirculation
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Top Perk > Amazing Efficiency

If you’re looking for a tankless water heater that uses less energy to deliver hot water when you need it, then you won’t a better choice than the Rinnai RUC98iN Ultra Series. This system has been described by many customers as the most energy efficient unit and we couldn’t agree less.

Besides being qualified by ENERGY STAR, this machine has an energy rating of 96% which obviously separates it in its own class. Just like other models from Rinnai, this unit gives you a range of choices for PVC and concentric venting, though without recirculation technology. It all depends on what you want.

In addition to its high energy factor, this unit also produces lower emissions of CO2 and NOX through an advanced technology. Though not highly priced like the RUR98iN model, it still offers a great value

  • 9.8/10
    Efficiency - 9.8/10
  • 8.8/10
    Ease of Use - 8.8/10
  • 9.2/10
    Value - 9.2/10
  • 9.2/10
    Features - 9.2/10


Cost: $$$$

Model Number: RUC98iN

Weight: 82 pounds

Size: 10 x 18.5 x 26 inches (Twin Pipe/Ultra)

Water Consumption: 9.8 gallons

Water Flow Rate: 9.8 gallon per minute (GPM)

Usage: Indoor

Fuel Type: Natural Gas

Similar model: RUR98iN

Warranty: Residential: Limited 12-year on heat exchanger, 5-year on parts, and 1-year on labor (5-year optional on labor). Commercial: Limited 5-year on heat exchanger, 5-year on parts, and 1-year on labor (2-year optional on labor).



Tankless water heaters are important for households for two major reasons- they help prevent the wastage of water and also stop your bills from skyrocketing. Perhaps they do not require large tanks and so do not take up as much valuable space; this makes them more practical than hot water tanks for small homes.

But then, finding the right tankless water heater can be somehow overwhelming especially if you’re a first timer or you’re looking to replace your current heater with a more efficient unit.

The reason is not far-fetched- there are so many brands in the market and it will take more than an impressive sales gimmick to find the best products. Even when you come across a product you’re attracted to, you still need to hear from people who have used the product in order to make an informed decision. This is why a review is important.

One of the tankless water heaters that has attracted of interest from homeowners due to its high efficiency and superior performance is the Rinnai RUC98iN Ultra Series Tankless Water Heater. And it’s no surprise this unit is highly rated considering the fact that it’s a product of an industry benchmark, Rinnai.

Rinnai is a superior brand well known for producing top quality tankless water heaters over the years. And the Rinnai RUC98iN is just one of their many top grade products.

The Rinnai RUC98iN is equipped with a good number of advanced features that really separates it as a tankless water heater in its own class. With a GPM as high as 9.8 with a temperature rise of 50F, this natural gas powered water heater is perfect for nearly every home in the United States. It has a maximum BTU of 199,000 max BTU and option for concentric or PVC venting.

Though it doesn’t feature a recirculation technology, it comes with dual pipe that uses condensation technology for greater efficiency. By the way, you should consider getting a smaller model if you have a small family because you may find this system too powerful.

The Rinnai RUC98iN has a water flow of 9.8 GPM which is enough to simultaneously support multiple bathrooms or sinks without any noticeable drop.

The high efficiency of this unit, though at a cheaper price than the RUR98iN model, makes it the perfect budget choice if you want a tankless heater that will give your additional savings on your bills without compromising performance. It is very easy to install and use; which is not surprising considering the fact it’s a product from Rinnai. And with all its amazing perks, we had no choice but to include it first on our list of the best tankless water heaters.


Anything a regular tankless heater does, you can expect to get from the Rinnai RUR98iN and even more. The unit is specially designed to support the whole house with reliable delivery to multiple bathrooms (up to four) at the same time without any fluctuation in water flow provided the temperature outside is favourable.

You can also be rest assured that won’t be enough time to grow goose bumps while doing the dishes or laundry due to delayed supply of hot water. This system delivers on demand.

The addition of a special ultra-low NOX gas burner in the design of this unit tackles the emission problem. In order words, you can set it up inside the house without worrying about the release of harmful fumes within your home. This is one of the major advantages the Rinnai RUC98iN has over most of its competitors.

This model has a rated water flow rate up to 9.8 gallon per minute and can produce maximum power of 199,000 BTU, which explains why it’s mostly suitable for households.

But just in case you don’t have so much demand for hot water, you can reduce the power and flow rate through the modulating gas valve on the device. You can reduce the 190,000 BTU power to 15,200 BTU and the 9.8 GPM water flow rate to 0.26 depending on your specific needs.

In addition, this unit enables you to monitor and alter the heating settings through a control system. Though it doesn’t feature a recirculation technology, it comes with dual pipe that uses condensation technology that it ensures it also delivers a great performance.


As indicated earlier, the heat outflow of this unit is 9.8 GPM which may fluctuate depending on the weather condition outside the house. Generally, with cooler temperatures, you are likely to experience

As previously mentioned, you’ll enjoy up to 9.8 GPM with the RUC98IN. This number might fluctuate depending on the temperature outside.

The temperature of the unit can be anywhere between 98F to 185F depending on where you are using the system. In residential homes, you can expect temperature between 98F to 140F, with higher upper limit for office buildings at 185F.

The RUC98iN is also equipped with a programmable digital controller that allows you alter temperature and save energy in the process. You can use the remote control provided to adjust temperature to your preferred choice.

This unit has been labelled as an “ultra-efficient” heater and we can’t agree any less. Two heat exchangers are employed to adequately heat the incoming water in a condensing mode where the flue gases are used to preheat the water in the secondary heat exchanger. As a result, the exhaust temperature is greatly reduced leading to higher efficiency of the unit.


With the Rinnai RU98IN, installation is less of a hassle. But of course, you still require a basic technical knowledge to go through with the project.

An installation manual is provided which contains a detailed instruction on how to set up the system. You may also want to watch the video tutorial online.

However, if you don’t feel confidence to carry out the project especially if don’t have any DIY skill set, then you may want to consider hiring someone else to do the installation. We recommend hiring a Rinnai technician; and don’t worry, it won’t cost you much.

The Rinnai RUC98iN weighs 82 pounds and has a dimension of 10 x 18.5 x 26 inches which is not very massive when you compare it with most tanked options. So you will not require much space to install it. In order words, this can be installed almost anywhere.

Although you will be freely provided with special isolator valves, other components that are required to successfully set up the unit will have to be ordered by you.

Some of the things you will need to get started include:

  • Weather proofing equipment
  • Circuit breakers
  • Ground lines
  • Exhaust pipes

You may actually need other parts or less, depending on what you already have at home. Like we mentioned earlier, even though the installation has been made as simple as possible, you may want to hire a professional to do it for you because any little mistake can void the product warranty.

Other features

  • Twin pipe PVC/CPVC configuration for greater flexibility
  • Comes with safety features like thermal fuse, flame rod and combustion fan rpm check
  • Has boiling and frost protection
  • Has OHS and over-current protection.

You can follow any of the installation videos online.


  • Doesn’t require much space, so can be installed almost anywhere
  • Highly energy efficient
  • Delivers hot water on demand and doesn’t makes noise
  • Delivers up to 9.8 GPM which is pretty massive
  • Special system to greatly reduce NOX emission makes it super safe
  • Multiple applications- home or office buildings
  • Doesn’t require expansion kit
  • Great warranty
  • Comes with dual pipes for added efficiency
  • Very Silent


  • System requires venting during installation and no venting kit is provided
  • May be too powerful for small homes
  • You may need to hire a professional for installation
  • Requires scheduled maintenance by a certified repair personnel certified from Rinnai.

Frequently Asked Questions

Q: Which other parts are necessary besides purchasing the tankless heater itself?
A: You need isolators and special vent pipes to go thru the roof, and a roof jack.
Q: Does this come with the LP conversion kit?
A: No
Q: How many gallons per minute dose this produce?
A: Rinnai RUC98iN – at 75 degree rise you get 5 GPM; see page 50 of manual for graph
Q: Is there any reason an external circulation pump couldn't be installed with this model?
A: None. An external pump can he installed
Q: What is the difference between this model and the RL94iN?
A: The RL94 is a non-condensing model and is slightly less efficient. This model (indoor unit) must be vented using Rinnai vent pipe. The RU98in is a condensing model and requires a condensate line (very simple) and is very efficient. It also produces 9.8 gallons per minute as opposed to 9.4 Gallons.
Q: Does this come with a vent kit
A: No, it does not.
Q: What can I expect to pay for installation?
A: That depends on your building. Aside from mounting the heater and connecting the water pipes, there must be appropriate accommodations for air intake, exhaust venting, and condensate disposal.
Q: Can this heater handle the weather at high altitudes (e.g. 5200)?
A: Yes, it also has high altitude settings
Q: How fast is hot water delivered to multiple locations in a typical 2000 ft2 home and do I really need a recirculating system?
A: Less than 2 minutes and one unit should be fine for your needs.
Q: Does this unit have condensing technology?
A: Yes this is a condensing unit; it requires a condensate line and offers PVC venting option or Rinnai venting option.

The Bottom Line

If you have a large family and you’re looking for a powerful water heater that will meet your household needs, then the Rinnai RUC98iN will make a great buy. You will be fascinated by its great power and high energy efficiency, compact size and environmental friendliness. Though you may find the price a little too high, the value it provides makes it well worth the investment.  This unit is one of the best tankless heaters you can rely on to provide you with continuous supply of hot water whenever you need it, no matter how long. With this unit in your home, your bills will never skyrocket anymore!


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