Noritz 6.6 GPM 120,000 BTU Residential Natural Gas Outdoor Condensing Tankless Water Heater (.89 UEF)

The Noritz NRC661-OD-NG Residential 6.6 GPM 120,000 BTU Natural Gas Outdoor Condensing Tankless Water Heater delivers an endless supply of hot water while improving energy efficiency with a 0.89 UEF condensing design. Unlike traditional storage tank water heaters that continuously heat and store a limited amount of water, the NRC661-OD-NG heats water only when needed, helping reduce standby energy loss while providing reliable hot water for showers, sinks, and household appliances.

Designed specifically for outdoor installation, the NRC661-OD-NG eliminates the need for traditional venting while providing a 120,000 BTU heating capacity and up to 6.6 GPM of hot water delivery. With advanced condensing technology, a compact wall-mounted design, and durable internal components, this Noritz tankless water heater provides dependable performance, space savings, and long-term efficiency for residential natural gas applications.

Product Features:

• 120,000 BTU Input: Provides reliable natural gas heating capacity for continuous, on-demand hot water.
• Up to 6.6 GPM Flow Rate: Supplies hot water to multiple fixtures, including showers, sinks, and appliances, depending on incoming water temperature and household demand.
• 0.89 UEF Condensing Efficiency: High-efficiency condensing technology captures additional heat from combustion gases to help reduce energy consumption and improve overall performance.
• Outdoor Installation: Designed for outdoor installation without the need for traditional venting, helping simplify installation and reduce venting costs.
• Compact Wall-Mounted Design: Saves valuable floor space compared to conventional tank water heaters while providing an unlimited supply of hot water.
• Durable Heat Exchanger: Engineered with reliable internal components to provide consistent performance and long service life.
• Freeze Protection: Built-in protection features help safeguard the unit during colder conditions when installed according to manufacturer requirements.
• Energy Star® Certified: Meets high-efficiency performance standards to help reduce utility costs while maintaining dependable hot water delivery.
• Multiple Unit Capability: Compatible with optional accessories that allow multiple units to be connected for increased hot water capacity in larger applications.

What Is an Isolation Valve Kit?

An isolation valve kit is an important accessory used during tankless water heater installation. These valves connect to the hot and cold water lines and allow the water heater to be shut off, serviced, flushed, or descaled without turning off water service to the entire home.

Isolation valves are especially important for tankless water heaters because routine maintenance helps preserve efficiency and extend the life of the heat exchanger. Over time, mineral buildup can collect inside the unit, especially in areas with hard water. Isolation valves make flushing and descaling faster and more convenient for both homeowners and service professionals.

Short vs. Long Isolation Valve Kit

For this Noritz NRC661-OD-NG tankless water heater, you only need to select one isolation valve kit based on your installation application.

• IK-WV-200-5-TH-S Short Isolation Valve Kit: A shorter valve kit designed for installations where space is limited or a more compact plumbing connection is preferred.
• IK-WV-200-5-TH-L Long Isolation Valve Kit: A longer valve kit designed for installations where additional clearance or easier service access is needed.

Both valve kits include 3/4" threaded isolation valves and a lead-free male pressure relief valve. The correct choice depends on available space, piping layout, and servicing preferences.

Understanding Tankless Water Heater Sizing

Unlike traditional storage tank water heaters, tankless water heaters are sized by flow rate (GPM) and temperature rise, not by tank capacity. Flow rate is the amount of hot water the unit can produce each minute, while temperature rise is the difference between your desired hot water temperature and the incoming groundwater temperature.

When sizing a tankless water heater, always use your winter groundwater temperature, as colder incoming water requires more heating. As the required temperature rise increases, the maximum available flow rate decreases.

For example, if your desired water temperature is 120°F and your winter groundwater temperature is 55°F, the required temperature rise is:

120°F - 55°F = 65°F Temperature Rise

Use the Flow Rate Chart in the product images to determine how much hot water the NRC661-OD-NG can produce at your required temperature rise. This helps ensure the unit is properly sized for your home's showers, faucets, dishwashers, washing machines, and other hot water demands.

Warranty

This product includes a manufacturer's limited residential warranty, including up to 12 years on the heat exchanger, 5 years on parts, and 1 year of reasonable labor coverage for qualifying residential installations. Always verify fuel type, installation location, electrical requirements, water quality, required accessories, and local plumbing and mechanical codes prior to installation.