Noritz 5.0 GPM 120,000 BTU Residential Natural Gas Outdoor Tankless Water Heater (.82 UEF)

The Noritz NR501-OD-NG 5.0 GPM 120,000 BTU Residential Natural Gas Outdoor Tankless Water Heater delivers dependable, on-demand hot water in a compact, energy-efficient design that's ideal for apartments, condominiums, townhomes, and smaller single-family homes. Unlike traditional storage tank water heaters that continuously heat and store a limited amount of hot water, the NR501-OD-NG heats water only when a hot water fixture is opened, providing an endless supply of hot water while helping reduce standby energy loss.

Designed exclusively for outdoor installation, the NR501-OD-NG requires no additional venting, helping simplify installation while preserving valuable indoor space. Delivering up to 120,000 BTU of natural gas heating power and a maximum flow rate of 5.0 gallons per minute, this compact wall-mounted tankless water heater provides reliable hot water for homes with one to two bathrooms. Its commercial-grade copper heat exchanger, fully modulating burner, built-in freeze protection, and user-friendly temperature controls offer dependable performance and long-lasting durability.

Product Features:

• 120,000 BTU Maximum Input: Provides dependable natural gas heating capacity for everyday residential hot water needs.
• Up to 5.0 GPM Flow Rate: Supplies continuous hot water for showers, sinks, dishwashers, and washing machines depending on incoming water temperature and simultaneous household demand.
• Outdoor Installation: Designed exclusively for outdoor installation, eliminating the need for vent piping while helping simplify installation.
• Non-Condensing Design: Delivers reliable on-demand performance with a Uniform Energy Factor (UEF) of 0.82 while heating water only when needed.
• Commercial-Grade Copper Heat Exchanger: Heavy-duty copper heat exchanger is engineered for long-lasting residential durability and dependable heat transfer.
• Compact Wall-Mounted Cabinet: Small footprint helps maximize indoor living space while providing convenient outdoor installation.
• Adjustable Temperature Settings: Factory default temperature is 120°F with additional selectable settings of 130°F, 135°F, and 140°F for residential applications.
• Fully Modulating Burner: Automatically adjusts between approximately 15,000 and 120,000 BTU to help maintain consistent outlet water temperatures while improving fuel efficiency.
• Built-In Freeze Protection: Helps protect the unit during cold weather when installed according to Noritz requirements and connected to electrical power.
• Advanced Safety Features: Includes flame sensing, overheat protection, fan rotation monitoring, lightning protection, temperature lockout, high elevation adjustment, and self-diagnostic monitoring for dependable operation.

What Is an Isolation Valve Kit?

An isolation valve kit is a recommended accessory for every tankless water heater installation. These valves connect to the hot and cold water lines and allow the unit to be isolated for flushing, descaling, maintenance, or servicing without shutting off water to the rest of the home.

Routine flushing helps remove mineral buildup that naturally accumulates inside the heat exchanger, especially in hard water areas. Installing isolation valves simplifies maintenance while helping preserve efficiency, maintain performance, and extend the life of the water heater.

Short vs. Long Isolation Valve Kit

For the Noritz NR501-OD-NG, only one isolation valve kit is required based on the available installation space.

• IK-WV-200-5-TH-S Short Isolation Valve Kit: Ideal for installations where limited space requires a compact plumbing layout.
• IK-WV-200-5-TH-L Long Isolation Valve Kit: Recommended when additional clearance is available, making future maintenance and servicing more convenient.

Both isolation valve kits include durable 3/4-inch threaded hot and cold isolation valves along with a lead-free pressure relief valve. The appropriate kit depends on your installation layout and available working space.

Understanding Tankless Water Heater Sizing

Unlike traditional storage tank water heaters, tankless water heaters are sized using flow rate (GPM) and temperature rise rather than storage capacity. Flow rate represents the amount of hot water the unit can produce each minute, while temperature rise is the difference between the incoming groundwater temperature and your desired outlet water temperature.

Always size a tankless water heater using your area's winter groundwater temperature, since colder incoming water requires more heating capacity and reduces the maximum available flow rate.

For example, if your desired hot water temperature is 120°F and your incoming groundwater temperature is 50°F, the required temperature rise is:

120°F − 50°F = 70°F Temperature Rise

Use the Noritz flow rate chart included with the product literature to determine the expected hot water output at your required temperature rise. This helps ensure the water heater is properly sized for your household's simultaneous hot water demand.

Warranty

The NR501-OD-NG includes Noritz's residential limited warranty featuring a 12-year heat exchanger warranty for standard residential installations, a 5-year parts warranty, and a 1-year reasonable labor warranty. When used with a recirculation system, the heat exchanger warranty is reduced to 3 years. Always verify natural gas supply, installation location, water quality, electrical requirements, local plumbing and mechanical codes, and all required accessories prior to installation.