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Rinnai RUC98IN Review – (Twin Pipe / Natural Gas or Propane)

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Rinnai-RUC98iN-Ultra-Series-Natural-Gas-Tankless-Water-HeaterThe Rinnai RUC98IN Ultra Series is a gas-powered indoor tankless water heater suitable for residential and commercial use. The water heater weighs 61.7 pounds, with a height of 26 inches and 10 inches wide. The control panel features a digital display, gas and water control, as well as a power button. One unique feature of this unit is that you can lock the temperature button.

The Rinnai RUC98IN can use twin-pipe or concentric PVC venting options and its gas, and water supply inlets and outlets are bigger than most heaters in its class. On standby mode, the heater consumes 2 watts of power. When it is working, its power consumption is 64 watts, and this can rise to 146 watts during winter. The Rinnai RUC98IN uses an electric ignition system instead of a pilot light that consumes more energy.

Energy Star

The Rinnai RUC98IN is one of the top Energy Star certified water heaters and has an energy factor of 0.95, making it one of the most energy-efficient gas-powered tankless water heaters. The unit has a wide minimum to maximum gas burn rate ranging from 15,200-199,000 Btu and hot water flow rate that ranges from 0.26 to 9.8 GPM and an extremely low minimum activation flow rate of 0.4 GPM. With these features, the Rinnai RUC98IN can effectively support the simultaneous use of multiple faucets without interruption in large households.

The residential model can heat water up to 95-140 degrees Fahrenheit while the commercial model has a heating capacity of up to 185 degrees Fahrenheit. The Rinnai RUC98IN is a powerful gas tankless water heater that can use natural gas or propane, but it is an expensive machine.

In addition to the initial cost of buying the unit, the installation is also expensive as it often requires new water and gas pipes and professional installation. Plus, maintenance must be performed by Rinnai-certified technicians.

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The Rinnai RUC98IN offers a variety of advantages over many of its contemporaries in the tankless water heater market. In addition to being energy efficient, it also features advanced technological innovations to ensure you get hot water on demand at all times. Here are some of the great selling points of this unit.

  • Consumes Less Energy

    With an energy efficiency of 95 percent, the Rinnai RUC98IN is one of the most energy efficient in its class. This excellent rating means the heater uses almost all its energy to heat the water, with only a five percent waste. Thus, you need far less energy to operate the heater, effectively reducing your energy bills.

  • Compact and Space Size

    In today’s highly expensive property market, every square meter is a luxury, and nobody needs an oversized water heater unit taking up precious space. The Rinnai RUC98IN comes in a sleek, compact container that makes installation flexible and easy regardless of the size of the space.

    Due to its compact construction, you can install the Rinnai RUC98IN in your bathroom, or close to the point of use to facilitate faster delivery of hot water, increase efficiency and reduce energy loss. The small size is because tankless water heater units do not have to store water in place. And this makes it easier to install them in or out of your home. If space is a luxury in your home, you will have no problem fixing the Rinnai RUC98iN as it comes in a small package but packs a heavy punch.

  • On-demand Hot Water

    How does it feel to open the hot water faucet and have an instant gush of sizzling hot water? It feels great! Unlike conventional storage tank water heaters that have to store and reheat the water for several minutes when the water in the heater is depleted, a tankless water heater like the Rinnai RUC98IN provides hot water when you need it. The feat is achieved by heating the water directly as it passes through the unit rather than first storing it in a tank before heating. If you want hot water without having to wait for it, then the Rinnai RUC98IN is one of the best in its class.

  • High Volume Output

    At 9.8 gallons per minute, the Rinnai RUC98IN has one of the highest levels of output in its class. With this amount of hot water output, the unit can serve up to five showers or water outlets simultaneously without any troubles. It will make an ideal choice for large households or places where the need for hot water is high.

  • Reduced Risk of Contamination

    Because the Rinnai RUC98IN does not need to store water, the water does not sit for long periods, reducing the chances of bacterial contamination significantly. With a tankless unit like this product, you can rest assured of the quality of the water for human use.

  • Advanced Features

    The unit features an intuitive temperature control which allows you to set the ideal hotness you desire. Also, the Rinnai RUC98IN is extremely quiet during operation, making it an excellent appliance for people who love their peace.


Despite its many advantages, the Rinnai RUC98IN is not without a few shortcomings. Here are some of the drawbacks found in this product.

  • Temperature Drop

    The water temperature of the Rinnai RUC98IN may drop when it is serving more than one water outlet. The good news is that the temperature is back to normal a few seconds after.

  • May Take a While to Heat

    Due to its high GPM and heating temperature, the unit may take a while to heat the water, especially after it has not been used for an extended period.

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The Rinnai RUC98iN features innovative technology, compact and sleek design, high water output and best-in-class energy efficiency. This unit is definitely energy efficient. It can also provide hot water on demand for large households and is easy to install. Additionally, you can choose two venting options. If you need high output, high-efficiency tankless water heater, the Rinnai RUC98IN is worth considering.

by Water Heater Mag

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