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Rinnai RUC98iN Ultra Series Review


This Rinnai water heater is a concentric model which has an option of PVC venting. You can be assured that this unit is an eco-friendly product as it produces ultra-low NOx emissions. This system is characterized by 95% thermal efficiency; it works with natural gas and is capable of up to 199,000 BTU. To be exact, the temperature that it can achieve is from 98 to 140 degrees for residential use and from 98 to 185 degrees for commercial use. Because this water heater’s efficiency is rated with a 0, 96 energy factor, and a 0,92 uniform energy factor, it is not surprising that it is Energy Star certified.

There is an MC-91-2US controller included in the package. However, the commercial controller must be purchased separately. When you decide whether to get this product, take into account that it must be installed only indoors. Of course, this shouldn’t be an issue as its space-saving design allows for indoor installation. If your other pieces of the appliance at home have a metallic finish, this device will perfectly match them.

What Does It Do?

Rinnai RUC98iN Ultra Series Gas Tankless Water HeaterThanks to the condensing technology of this high-tech tankless water heater, it is a highly efficient product. Apart from being efficient, this item will also help you use less energy and spend less money on it. The heater requires a condensate line and offers a PVC venting option or a Rinnai venting one. As it is said in the description of this unit, it can work both with concentric and twin-pipe PVC venting. If you have room for only one pipe, then you need to use the concentric option. However, you should bear in mind that concentric PVC is expensive.

The Content of the Package

  • A tankless water heater;
  • Isolation valves;
  • A pressure relief valve

Attention – the valves are wrapped into the Styrofoam packaging, so you should be careful not to throw them away.

Keep in mind that the commercial controller is not included in the package, and you should buy it separately. There is also no flush kit in the set.


Voltage: 120 volts

Weight: 61,7 lbs

Size: twin Pipe/Ultra

Flow rate: 9.8 GPM

Water consumption: 9. 8 Gallons

Width: 18.5″

Height: 26″

Depth: 10″

Gas Connection: 3/4″

Water Connection: 3/4″

Warranty: Residential use: Limited 12-year on heat exchanger, 5-year on parts, 1-year on labor; Commercial use: Limited 5-year on heat exchanger, 5-year on parts, 1-year on labor

What to Expect?

Whenever the device senses any need for flushing, it is supposed to display a trouble code. To flush the heater, you don’t need any special kit. You just have to hook up a pump to circulate 4 gallons vinegar per minute through the unit for approximately one hour. As this product is a condensing one, it doesn’t need a condensation trap kit. You should be warned that your heater should be installed by a licensed professional if you want to be able to use the warranty. You also need to register the unit through the website once you have it installed so that you can use the warranty if needed. Due to the fact that the firebox is encased and very well insulated, the unit is very quiet. Reportedly, this heater is quieter than your furnace. You can only hear some noise resembling the one of a small fan when the device is actively heating.


  • As this tankless water heater has its box encased and insulated, it is exceptionally quiet even when actively heating.
  • Thanks to its compact design, this unit can be installed indoors without depriving you of your space at home.
  • This water heater is an eco-friendly one as it produces ultralow NOx emissions. So if you are concerned about the environment, this is a good product to consider.
  • With this item, Rinnai gives you the options for both concentric and PVC venting.


  • A disadvantage is that the concentric exhaust requires additional original equipment manufacturer parts, which adds to the product’s initial cost.

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