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Rinnai RUC98i Series – RUC98iP/RUC98iN Tankless Water Heater Review

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Rinnai Corporation was founded in 1920 in Nagoya, Japan. Its subsidiary, Rinnai America Corporation was established in Peachtree City, GA in 1975.

Rinnai is the leading seller of tankless water heaters in North America. Rinnai is known for its products equipped with superior quality, safety, technology, and sophisticated control systems.

The Rinnai RUC98i is a gas tankless water heater that comes in two different models. The RUC98iN uses natural gas as the fuel, whereas, the RUC98iP uses propane to heat water.

It is capable of saving up to 96% of energy and is commonly used for residential water heating purposes. Its compact design allows for the indoor installation of this product.

Key Specifications

Rinnai RUC98iN Ultra Series Natural Gas Tankless Water Heater, Twin Pipe The Rinnai RUC98i is an indoor installation type gas tankless water heater that Energy Star qualified. It is capable of producing a maximum flow rate of 9.8 GPM.

The temperature of the hot water can be set from a range of 98˚F to 140˚F without affecting the output flow rate.

This product has low NOx emissions of the order 20ppm and it adheres to the standards set by the South Coast Air Quality Management.

Two variations of this model that use propane and natural gas for fuel are available –

Key Specifications – Rinnai RUC98iN / Rinnai RUC98iP

Some of the other main specifications of this product are as shown below – 

Parameter Specification
Dimensions 10 × 18.5 × 26 inches
Weight 82 pounds
Uniform Energy Factor 0.92
Service connections ¾ inches MNPT
Minimum Water supply pressure 50 psi
Maximum Water supply pressure 150 psi
Minimum Gas rate (input) 15,200 BTU/h
Maximum Gas rate (input) 199,000 BTU/h
Appliance 120 V AC, 60 Hz
Temperature controller 12 V DC
Electrical consumption on Normal Mode 75 W
Electrical consumption on Stand-by Mode 2 W
Electrical consumption on Anti-freeze protection Mode 146 W
Amperage With pump (max) 8 A
Amperage Without pump (max) 4 A
Fuse 10 A

Assembly / Installation

The Rinnai RUC98i series requires connections dedicated venting and condensate discharge, making it a little harder to install than electric type tankless water heaters.

However, if you are certain that you will be able to carry out the process yourself, then proceed with the installation yourself.

Otherwise, contact a trained professional.

The rudimental steps in the installation procedure are choosing the installation location, mounting, connecting the plumbing, exhaust, and electrical lines, and installation of the temperature controller.

Ensure that you adhere to the gas and electrical local or state codes during installation.



The warranty period for the Rinnai RUC98i series heat exchangers is 12 years when used for residential applications, 5 years for commercial applications and 10 years for residential and space heating applications.

The parts are covered under warranty for 5 years and a 1-year warranty period is allowed for labor.

The warranty is reduced to 3 years if the product is used as a circulating heater within a circulation loop. There are also several instances that could void your warranty.

So, read the terms carefully before installing the product.

To avail warranty, contact your place of purchase, visit the Rinnai website (www.rinnai.us), place a call to Rinnai at 1‐800‐621‐9419 or write to Rinnai at 103 International Drive, Peachtree City, Georgia 30269.

Consumer Comments

Customers who have installed the RUC98iP / RUC98iN are quite content with the performance of the unit.

Not only does it have a greater energy efficiency than most other gas tankless models, but it is also able to produce enough hot water for an entire house.

Most users have reckoned that the unit is pretty easy to install for a whole house unit and the warranty terms are not terminated if the users install the heaters themselves.

Apart from the ease of installation, operating the unit is also simple due to the user-friendly control buttons and the digital display on the heater.

Consumers are happy with the space-saving and sleek design and the noiseless operation of the heater which is not very common in tankless water heaters.

While most customers are satisfied with the product, a few have had trouble trying to avail the warranty services. Some users also feel that the temperature of the output water is not hot enough.

However, if you purchase the product after proper sizing and follow the instructions in the manuals carefully, this product can help save a lot of energy and money.



Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe
120 Reviews
Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe
  • INDOOR installation only. Fuel Type: NATURAL GAS.
  • Concentric or PVC venting option
  • Up to 0.96 Energy Factor/Up to 0.92 Uniform Energy Factor



  • It is capable of providing hot water to an entire household.
  • It saves a lot of energy during operation and is Energy Star certified. A significant amount of money can be saved on utility bills with the use of this product.
  • Its NOx emissions are lower than 20 ppm, and its electrical ignition system does not use up much fuel making it an environment-considerate choice.
  • It operates without much noise.


  • It is bulkier and a little expensive than other tankless water heaters.
  • It requires frequent maintenance to be done by Rinnai-certified professionals which can be a costly procedure.
  • Upgrades to your home may be necessary for installation.


Recommended Accessories

Condensing Vent Pipe

Condensing vent pipe extension can be used to withstand the flue temperature variations that may occur after constant use of the product. Rinnai 224087PP Condensing Vent Pipe Extension, 10-Inch


Remote Controller for the Temperature Controller Module Rinnai MC-91-2S Standard Remote Controller - Residential or Commercial, 98-Degree -140-Degree F, Silver



Why is there no Hot Water when I Turn on the Tap?

Although the product heats water instantaneously, it does not deliver hot water instantly due to the cold water already present in the pipes. This can be dealt with by using a recirculating pump.

What is the Life Expectancy of this Tankless Water Heater?

It can last up to 20 years. However, the performance of the unit varies depending on the quality of installation, maintenance, water, and environmental conditions.

What is the Difference between RUC98i and RUC98iN?

RUC98i is the model name of the gas tankless water heater. The N in RUC98iN represents natural gas which is the type of fuel that can be used for that model.

Can this unit be Installed in a Crawl Space?

The unit can be installed in small spaces only if there are adequate adjustments done for air circulation and exhaust.

Does this unit come with a Flush Kit?

No. Rinnai does not provide flush kits for any products. Flush kits can be purchased from other manufacturers or you can contact Rinnai for assistance during flushing.

Our Recommendation

The Rinnai RUC98i has a maximum flow rate of 9.8 GPM and is capable of providing an endless supply of hot water. It emits low levels of pollutants into the atmosphere and has an energy efficiency of 96%.

Rinnai’s RUC98i is ideal for medium to large households that require a large amount of hot water and also for some commercial applications. It can also be combined to use for space heating purposes.

This product is an excellent choice for people who are looking to save energy and money on their water heaters.


Last update on 2022-12-01 / Affiliate links / Images from Amazon Product Advertising API

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